What is phosphoric acid

Phosphoric Acid (H₃PO₄) is a clear colorless liquid or transparent crystalline solid, an odorless phosphorus-containing strong inorganic acid. Phosphoric acid contains not less than 85% of H₃PO₄. Phosphoric acid is a sequestering agent which binds many divalent cations, including Fe++, Cu++, Ca++, and Mg++. Phosphoric acid is used in dentistry and orthodontics as an etching solution, to clean and roughen the surfaces of teeth where dental appliances or fillings will be placed. In addition, phosphoric acid is a constituent in bone and teeth, and plays a role in many metabolic processes. Phosphoric acid liquid is usually an 85% aqueous solution. Shipped as both a solid and liquid. Corrosive to metals and tissue. Phosphoric acid is also used in making fertilizers, detergents and in foods and beverages processing, water treatment, pickling and rust proofing metals, and for many other purposes. Phosphoric acid also used in photography (platinum printing) and as a wet etchant in semiconductor manufacturing at a standard concentration of 85%.

Phosphorus-containing substances occur very widely in natural foods usually as free phosphoric acid or as the potassium, sodium or calcium salts. Phosphate is found in highest concentrations (0.1-0.5% or more, in terms of phosphorus) in such foods as milk, cheese, nuts, fish, meat, poultry, eggs (yolk), and certain cereals ¹.

Phosphoric acid in food is used as a sequestrant, an antioxidant and a “synergist” for other antioxidants; also as an acidulant and flavor in beverages and fruit
products ¹.

Figure 1. Phosphoric acid

What does phosphoric acid do?

Phosphoric acid is an essential constituent of the human organism, not only in the bones and teeth, but also in many enzyme systems. Phosphorus plays an important role in carbohydrate, fat and protein metabolism.

The daily intake of phosphate necessary for human lies between 1 and 2 g ¹. Insufficient supply of phosphate produces deficiency in the bones. Since the phosphate concentration of serum and tissues is maintained by physiological regulations, the intestinal absorption depends on requirements and is therefore limited. Doses of 2 to 4 g act as weak saline cathartics. Excretion takes place mainly in the feces as calcium phosphate, so that the continuous use of excessive amounts of sodium phosphate and phosphoric acid may cause a loss of calcium ¹.

There have been a great many publications on phosphorus metabolism, on the interrelationships of calcium and phosphorus in foods and nutrition and on the impact thereon of the use of phosphate as a food additive.

Low-quality evidence from 1 study ² showed that patients (any kidney stone type) with baseline soft drink consumption of more than 160 mL per day who were instructed to abstain from drinking soda had a reduced risk for symptomatic kidney stone recurrence compared with no treatment (33.7% vs. 40.6%). Subgroup analysis showed that the benefit was limited to patients who drank soda that was acidified by phosphoric acid (typically colas) rather than those acidified by citric acid (typically fruit-flavored sodas) (29.7% vs. 45.6%). Therefore decreasing soft drink intake in people with a high baseline intake of soft drinks acidified by phosphoric acid also decreased kidney stone recurrence ³.

Is phosphoric acid bad for you?

According to the Joint The Food and Agriculture Organization of the United Nations and the World Health Organization Expert Committee on Food Additives ⁴, “there is ample evidence to support the safety of the addition of small quantities of phosphoric acid to food. Thus, the use of 0.01-0.02% as a sequestrant, an antioxidant or “synergist” inantioxidant mixtures should present no health hazards whatsoever”.

The Joint The Food and Agriculture Organization of the United Nations and the World Health Organization Expert Committee on Food Additives ⁴, further added, “the use of phosphoric acid to compensate for deficiency of fruit acidity, as a flavor component and in other ways, essentially within the “normal” concentration of phosphates naturally occurring in foods, should present no problem”.

Estimate of acceptable daily intakes for man ⁴:

• Unconditional acceptance 0-5 mg/kg body-weight
• Conditional acceptance 5-15 mg/kg body-weight

The total dietary intake of phosphorus from both foods and food additives should not exceed ⁴:

• Unconditional acceptance up to 30 mg/kg body-weight
• Conditional acceptance 30-70 mg/kg body-weight

A report by the U.S. Food and Drug Administration [FDA] ⁵ found that high phosphate intakes can affect calcium distribution in the body and may in some cases produce soft tissue calcification and affect bone formation. Kidney damage, soft tissue calcification and bone effects were the main findings in laboratory animals fed phosphates ⁶. However, such effects were not observed in studies in humans, except in pa-tients with end stage renal disease. In ill individuals, hypophosphatemia is caused by vomiting and se-vere diarrhoea, and is associated with various liver diseases ⁷.

In the same FDA report ⁵, the FDA found no conclusive evidence of reproductive effects has been demonstrated in feeding studies with phosphate salts in animals. No carcinogenic potential was demonstrated in feeding studies in rats treated with phosphates; however several phosphates have been shown to
promote the effects of known carcinogens in rodents. Genotoxicity assays have yielded essentially negative results with phosphate salts ⁵.

Human Toxicity Studies

Studies on 15 students, who drank 2000-4000 mg of phosphoric acid in fruit juices every day for 10 days, and on 2 males who received 3900 mg of phosphoric acid every day for 14 days, revealed no observable change in urine composition indicative of a disturbed metabolism ⁸.

Consumption of soft drinks containing phosphoric acid has been linked to the recurrence of urinary stones in adult men ⁹. The mechanism is likely to involve increased calcium phosphate precipitation ⁹.

15 non-smoking adults aged 18-36 years were exposed to phosphoric acid aerosols. No airways irritation was reported at a concentration of 1.6 mg/m³. 18% of subjects reported airways irritation at 7.2 mg/cu m and 82% at 11.0 mg/m³ ¹⁰.

In a study in which the daily basal diet of 4 men contained 450 mg calcium and 1400 mg phosphorus, supplementation with 750 mg phosphorus as phosphoric acid for 1 week resulted in a slight decrease in urinary excretion of calcium. When the treatment was continued for 12 weeks, there was a further decrease in urinary calcium excretion ⁴.

A 42 year-old man presented with oropharyngeal burns and hematemesis one hour after ingesting 240 mL phosphoric acid. Endoscopy revealed moderate distal esophagitis and severe proximal gastritis. The duodenum was normal. The gastric injuries healed completely ¹¹.

A 64 year-old man ingested 90-120 mL 20% hydrogen phosphate in attempted suicide. On admission one hour later he complained of a burning throat, hoarseness, mild abdominal pain and nausea. He had watery stools and vomited approximately 100 mL blood-stained liquid. The posterior pharynx was inflamed with discrete patches of mucosal pallor, the abdomen tender and the stool contained blood. Patient developed hyperphosphatemia, hypocalcaemia and a metabolic acidosis. Serum concentrations of calcium and phosphate were 2.05 mmol/L and 2.3 mmol/L respectively. Arterial blood gas analysis showed pH 7.19, HCO3- 6 mmol/L and an anion gap of 23 mmol/L. These abnormalities resolved within 36 hours following intravenous fluid and sodium bicarbonate plus oral aluminium hydroxide (as a phosphate binder). The patient recovered fully ¹¹.

Phosphoric acid (orthophosphoric acid, metaphosphoric acid) topically may irritate and injure the eyes, owing to its acidity, but systemically phosphate has no poisonous action on the eye ¹². Tested on human eyes, 0.16 M orthophosphoric acid buffered to pH 2.5 caused moderate brief stinging sensation but no injury when applied as a single drop. A drop of the same solution adjusted to pH 3.4 caused no discomfort.

A railroad accident in Somerville, Massachusetts led to a phosphorus trichloride liquid spillage ¹³. Attempted clean up with water led to the liberation of phosphorus trichloride, phosphorus acid, hydrogen chloride, and phosphorous oxides. Seventeen people exposed to this mixture were studied. Patients experienced eye irritation, lacrimation, nausea, vomiting, and dyspnea. Six patients had transient lactic dehydrogenase elevation. Although all patients had normal chest roentgenographic findings, pulmonary function tests showed statistically significant decreases in vital capacity, maximal breathing capacity, and forced expiratory volume vital capacity in those closest to the accident site. Patients exposed < 1.5 hour had significantly greater maximal expiratory flow rates at 25% of vital capacity when compared with patients who had been exposed longer. In seven patients, repeated pulmonary function tests one month later showed improvement, suggesting that the acute effects may have been due to phosphorus acid toxicity ¹³.

Phosphoric acid at high concentrations is corrosive to all tissues with which it comes in contact. It can cause severe skin burns at concentrations of 75% or greater. Inhalation of the vapor or mist can cause eye, nose, throat, and respiratory irritation or coughing. When ingested, it can produce nausea, vomiting, abdominal pain, bloody diarrhea, acidosis, shock, and irritation or burns of the oropharyngeal mucosa, esophagus, and stomach.

When used as an agent for metal cleaning, phosphoric acid may react with impurities in the metal and release phosphine gas.

Phosphoric acid toxicity

Ten to 25 per cent phosphoric acid solutions are irritant and more concentrated solutions corrosive.

Skin exposure, inhalation or ingestion of any quantity of a concentrated solution can be dangerous.

5 mL of a 1.0 per cent phosphoric acid solution was not caustic to the oral mucosa ¹⁴. A patient has survived ingestion of 90-120 mL of a metal cleaner containing 20 per cent “hydrogen phosphate” ¹⁵.

Skin

• Solutions greater than 10 per cent phosphoric acid are irritating to the skin and higher concentrations may cause burns.

Eyes

• Direct contact with phosphoric acid may irritate or burn the eye causing pain, blepharospasm, lacrimation and/or photophobia.

Inhalation

• Cough and retrosternal discomfort may be the only early features following phosphoric acid inhalation. Following significant exposure hoarseness, dyspnea (shortness of breath) and stridor (due to laryngeal edema) may develop. In the most severe cases the onset of non-cardiogenic pulmonary edema with increasing breathlessness, wheeze and cyanosis may be delayed for up to 36 hours.
• Bronchitis was reported in 46% and an obstructive lung function defect in 37% of 35 workers at a phosphoric acid production plant ¹¹.
• A patient with no previous history of asthma developed wheeze associated with chemical pneumonitis after accidental phosphoric acid inhalation. Evidence of airways hyper-responsiveness persisted one year later ¹¹.

Ingestion

• Ingestion of greater than 10 per cent phosphoric acid solutions will cause immediate burning of the mouth and throat possibly with retrosternal and abdominal pain, nausea and vomiting.
• Severe irritant or corrosive effects are likely following ingestion of greater than 20 per cent phosphoric acid solutions with hypersalivation, hematemesis (vomiting blood) and hypovolemic shock.
• There is a risk of gastric antrum ulceration, hemorrhage and perforation.
• The larynx may be burned, with edema causing airway obstruction.
• Obstructive symptoms due to esophageal or gastric stricture may develop weeks or months later.
• There is a single report of hyperphosphatemia, hypocalcemia and metabolic acidosis occurring after acute ingestion of 90-120 mL of 20 per cent phosphoric acid ¹⁵.
• Investigators described the death of one individual 19 days after ingestion of phosphoric acid as a result of recurrent internal hemorrhage. Necrosis of the and lower digestive tract and of the pancreas was evident at autopsy ¹⁶.

What is phosphoric acid used for?

The dominant use of phosphoric acid is for fertilizers, consuming approximately 90% of production ¹⁷.

Food additive

Food-grade phosphoric acid (additive E 338) is used to acidify foods and beverages such as various colas and jams ¹⁸. It provides a tangy or sour taste. Various salts of phosphoric acid, such as monocalcium phosphate, are used as leavening agents ¹⁷. Phosphoric acid in soft drinks has the potential to cause dental erosion ¹⁹. Phosphoric acid also has the potential to contribute to the formation of kidney stones, especially in those who have had kidney stones previously ²⁰.

Rust removal

Phosphoric acid may be used to remove rust by direct application to rusted iron, steel tools, or other surfaces. The phosphoric acid changes the reddish-brown iron(III) oxide, Fe2O3 (rust), to ferric phosphate, FePO4.

Liquid phosphoric acid may be used for dipping, but phosphoric acid for rust removal is more often formulated as a gel. As a thick gel, it may be applied to sloping, vertical, or even overhead surfaces. Different phosphoric acid gel formulations are sold as “rust removers,” “rust killers” or “naval jelly.” Multiple applications of phosphoric acid may be required to convert all rust. Rust may also be removed by phosphate conversion coating. This process can leave a black phosphate coating that provides moderate corrosion resistance such protection is also provided by the superficially similar Parkerizing and blued electrochemical conversion coating processes.

In dentistry

Phosphoric acid is used in dentistry and orthodontics as an etching solution, to clean and roughen the surfaces of teeth where dental appliances or fillings will be placed. Phosphoric acid is also an ingredient in over-the-counter anti-nausea medications that also contain high levels of sugar (glucose and fructose). This acid is also used in many teeth whiteners to eliminate plaque that may be on the teeth before application.

Other applications

Among many applications, phosphoric acid is used:

• As a solution for anodizing.
• As an external standard for phosphorus-31 nuclear magnetic resonance (31P NMR).
• As a buffer agent in biology and chemistry. For example, a buffer for high-performance liquid chromatography.
• As a chemical oxidizing agent for activated carbon production, as used in the Wentworth process.[20]
• As the electrolyte in phosphoric acid fuel cells.
• With distilled water (2–3 drops per gallon) as an electrolyte in oxyhydrogen generators.
• As a catalyst in the hydration of alkenes to produce alcohols, predominantly ethanol.
• As an electrolyte in copper electropolishing for burr removal and circuit-board planarization.
• As a flux by metal workers and hobbyists (such as model railroaders) as an aid to soldering.
• In compound semiconductor processing, phosphoric acid is a common wet etching agent: for example, in combination with hydrogen peroxide and water it is used to etch InGaAs selective to InP ²¹.
• Heated in microfabrication to etch silicon nitride (Si3N4). It is highly selective in etching Si3N4 instead of SiO2, silicon dioxide ²².
• As a cleaner by construction trades to remove mineral deposits, cementitious smears, and hard-water stains.
• As a chelant in some household cleaners aimed at similar cleaning tasks.
• In hydroponics pH solutions to lower the pH of nutrient solutions. While other types of acids can be used, phosphorus is a nutrient used by plants, especially during flowering, making phosphoric acid particularly desirable.
• As a pH adjuster in cosmetics and skin-care products.
• As a dispersing agent in detergents and leather treatment.
• As an additive to stabilize acidic aqueous solutions within a wanted and specified pH range.
• As a sanitizing agent in the dairy, food, and brewing industries ²³.
• As a main reactive agent in electrochemical weld cleaning.
• In soil organic carbon determination.

References

1. Eighth Report of the Joint FAO/WHO Expert Committee on Food Additives, Wld Hlth Org. techn. Rep. Ser., 1965, 309; FAO Nutrition Meetings Report Series 1965, 38. http://www.inchem.org/documents/jecfa/jecmono/v38aje10.htm
2. ShusterJJenkinsALoganCBarnettTRiehleRZacksonDet alSoft drink consumption and urinary stone recurrence: a randomized prevention trial., J Clin Epidemiol, 1992, vol. 45, pg. 911-6
3. Dietary and pharmacologic management to prevent recurrent nephrolithiasis in adults: A clinical practice guideline from the American College of Physicians”. Annals of Internal Medicine. 161 (9): 659–67. http://annals.org/aim/fullarticle/1920506/dietary-pharmacologic-management-prevent-recurrent-nephrolithiasis-adults-clinical-practice-guideline
4. WHO/FAO; Joint Expert Committee on Food Additives (JECFA): Phosphoric acid and phosphate salts (WHO Food Additives Series 17 http://www.inchem.org/documents/jecfa/jecmono/v38aje10.htm
5. GRAS Notice (GRN) No. 718 for Calcium acid pyrophosphate. https://www.fda.gov/downloads/food/ingredientspackaginglabeling/gras/noticeinventory/ucm593669.pdf
6. Sanderson, P. H. (1959) Functional aspects of renal calcification in rats, Clin. Sei., 18,67-79
7. Latner AL. 1975. Clinical biochemistry. Philadelphia: W.B. Saunders Co., 47-49, 279-315, 479, 842
8. WHO/FAO: Expert Committee on food additives. FAO Nutrition Meetings Report Series 38a for Phosphoric acid (7664-38-2) (1964). http://www.inchem.org/documents/jecfa/jecmono/v38aje10.htm
9. Shuster J, Jenkins A, Logan C, Barnett T, Riehle R, Zackson D, Wolfe. Soft drink consumption and urinary stone recurrence: A randomized prevention trial. J Clin Epidemiol 1992: 45: 911-6.
10. National Poisons Information Service; United Kingdom Poison Information Documents (UKPID): Phosphoric Acid (7664-38-2) (January 28, 1998). http://www.inchem.org/documents/ukpids/ukpids/ukpid73.htm
11. National Poisons Information Service; United Kingdom Poison Information Documents (UKPID): Phosphoric Acid (7664-38-2);January 28, 1998 http://www.inchem.org/documents/ukpids/ukpids/ukpid73.htm
12. Grant, W.M. Toxicology of the Eye. 3rd ed. Springfield, IL: Charles C. Thomas Publisher, 1986., p. 733
13. Phosphorus trichloride toxicity. Preliminary report. Am J Med. 1984 Dec;77(6):1039-42. https://www.amjmed.com/article/0002-9343(84)90185-2/pdf
14. von Muhlendahl KE, Oberdisse U, Krienke EG. Local injuries by accidental ingestion of corrosive substances by children. Arch Toxicol 1978; 39: 299-314.
15. Caravati EM. Metabolic abnormalities associated with phosphoric acid ingestion. Ann Emerg Med 1987; 16: 904-6.
16. American Conference of Governmental Industrial Hygienists. Documentation of the TLV’s and BEI’s with Other World Wide Occupational Exposure Values. CD-ROM Cincinnati, OH 45240-4148 2010
17. Klaus Schrödter, Gerhard Bettermann, Thomas Staffel, Friedrich Wahl, Thomas Klein, Thomas Hofmann “Phosphoric Acid and Phosphates” in Ullmann’s Encyclopedia of Industrial Chemistry 2008, Wiley-VCH, Weinheim. https://doi.org/10.1002/14356007.a19_465.pub3
18. EU Approved additives and E Numbers. https://www.food.gov.uk/business-guidance/eu-approved-additives-and-e-numbers
19. Dietary advice in dental practice. British Dental Journal volume 193, pages 563–568; 23 November 2002. https://www.nature.com/articles/4801628.pdf
20. Dietary and pharmacologic management to prevent recurrent nephrolithiasis in adults: a clinical practice guideline from the American College of Physicians. Ann Intern Med. 2014 Nov 4;161(9):659-67. doi: 10.7326/M13-2908. http://annals.org/aim/fullarticle/1920506/dietary-pharmacologic-management-prevent-recurrent-nephrolithiasis-adults-clinical-practice-guideline
21. Wet Chemical Etching. http://terpconnect.umd.edu/~browns/wetetch.html
22. Wolf, S.; R. N. Tauber (1986). Silicon processing for the VLSI era: Volume 1 – Process technology. p. 534. ISBN 0-9616721-6-1.
23. http://www.fivestarchemicals.com/wp-content/uploads/StarSanTech-HB2.pdf

What is calcium pantothenate

Calcium pantothenate is the calcium salt of the water-soluble vitamin B5 (pantothenic acid), ubiquitously found in plants and animal tissues with antioxidant property. Vitamin B5 (pantothenic acid) is an essential nutrient that is naturally present in some foods, added to others, and available as a dietary supplement. The main function of this water-soluble B vitamin is in the synthesis of coenzyme A (CoA) and acyl carrier protein ¹. Pentothenate is a component of coenzyme A (CoA) and a part of the vitamin B2 complex. Calcium pantothenate is a butyryl-beta-alanine that can also be viewed as pantoic acid complexed with beta alanine. Calcium pantothenate is used in the synthesis of coenzyme A (CoA) and protects cells against peroxidative damage by increasing the level of glutathione. Coenzyme A (CoA) may act as an acyl group carrier to form acetyl-CoA and other related compounds; this is a way to transport carbon atoms within the cell ². Coenzyme A (CoA) is important in energy metabolism for pyruvate to enter the tricarboxylic acid cycle (Kreb cycle) as acetyl-CoA, and for α-ketoglutarate to be transformed to succinyl-CoA in the cycle ³. Coenzyme A (CoA) is essential for fatty acid synthesis and degradation, transfer of acetyl and acyl groups, and a multitude of other anabolic and catabolic processes ⁴. Acyl carrier protein’s main role is in fatty acid synthesis ⁵. Vitamin B5 (pantothenic acid) is a growth factor and is essential for various metabolic functions, including the metabolism of carbohydrates, proteins, and fatty acids. This vitamin is also involved in the synthesis of cholesterol, lipids, neurotransmitters, steroid hormones, and hemoglobin.

Figure 1. Calcium pantothenate formula

Vitamin B5 is commercially available as D-pantothenic acid, as well as dexpanthenol and calcium pantothenate, which are chemicals made in the lab from D-pantothenic acid.

Calcium pantothenate uses

Pantothenic acid is frequently used in combination with other B vitamins in vitamin B complex formulations. Vitamin B complex generally includes vitamin B1 (thiamine), vitamin B2 (riboflavin), vitamin B3 (niacin/niacinamide), vitamin B5 (pantothenic acid), vitamin B6 (pyridoxine), vitamin B12 (cyanocobalamin), and folic acid. However, some products do not contain all of these ingredients and some may include others, such as biotin, para-aminobenzoic acid (PABA), choline bitartrate, and inositol.

Pantothenic acid has a long list of uses, although there isn’t enough scientific evidence to determine whether it is effective for most of these uses. People take pantothenic acid for treating dietary deficiencies, acne, alcoholism, allergies, baldness, asthma, attention deficit-hyperactivity disorder (ADHD), autism, burning feet syndrome, yeast infections, heart failure, carpal tunnel syndrome, breathing problems, celiac disease, colitis, pink eye (conjunctivitis), seizures, and bladder infections. It is also taken by mouth for dandruff, depression, diabetic nerve pain, enhancing immune function, improving athletic performance, tongue infections, gray hair, headache, hyperactivity, low blood sugar, trouble sleeping (insomnia), irritability, low blood pressure, multiple sclerosis, muscular dystrophy, leg cramps associated with pregnancy or alcoholism, general nerve pain, and obesity.

Pantothenic acid is also taken by mouth for osteoarthritis, rheumatoid arthritis, Parkinson’s disease, premenstrual syndrome (PMS), enlarged prostate, protection against mental and physical stress and anxiety, reducing side effects of thyroid therapy for people with decreased function of the thyroid gland, reducing signs of aging, reducing the risk of getting a cold or other infection, delayed growth, shingles, skin disorders, stimulating adrenal glands, sore mouth (stomatitis), chronic fatigue syndrome, toxicity related to medications such as salicylates or streptomycin, dizziness, constipation, and wound healing. It is also used following surgery to improve movement in the intestines and to reduce sore throat.

People apply dexpanthenol, which is made from pantothenic acid, to the skin for itching, promoting healing of mild eczemas and other skin conditions, insect stings, bites, poison ivy, diaper rash, and acne. It is also applied topically for preventing and treating skin reactions to radiation therapy. It is also applie to reduce skin reactions to radiotherapy treatment, for dry eyes and eye trauma, and for sprains.

Dexpanthenol is given with a needle in to the vein or muscle to improve intestinal movement (intestinal peristalsis), possibly following surgery of the gut, for abdominal bloating (distension) due to reduced intestinal function, and for gas following surgery or pregnancy.

A nasal spray containing dexpanthenol is used to reduce the feeling of having a stuffed nose (nasal obstruction) and to reduce a runny nose (nasal discharge).

Dietary supplements

Pantothenic acid is available in dietary supplements containing only pantothenic acid, in combination with other B-complex vitamins, and in some multivitamin/multimineral products ⁶. Some supplements contain pantethine (a dimeric form of pantetheine) or more commonly, calcium pantothenate ⁶. No studies have compared the relative bioavailability of pantothenic acid from these different forms. The amount of pantothenic acid in dietary supplements typically ranges from about 10 mg in multivitamin/multimineral products to up to 1,000 mg in supplements of B-complex vitamins or pantothenic acid alone ⁶.

Recommended Intakes

Intake recommendations for pantothenic acid and other nutrients are provided in the Dietary Reference Intakes (DRIs) developed by the Food and Nutrition Board at the National Academies of Sciences, Engineering, and Medicine ⁷. DRI is the general term for a set of reference values used for planning and assessing nutrient intakes of healthy people. These values, which vary by age and sex, include:

• Recommended Dietary Allowance (RDA): Average daily level of intake sufficient to meet the nutrient requirements of nearly all (97%–98%) healthy individuals; often used to plan nutritionally adequate diets for individuals.
• Adequate Intake (AI): Intake at this level is assumed to ensure nutritional adequacy; established when evidence is insufficient to develop an RDA.
• Estimated Average Requirement (EAR): Average daily level of intake estimated to meet the requirements of 50% of healthy individuals; usually used to assess the nutrient intakes of groups of people and to plan nutritionally adequate diets for them; can also be used to assess the nutrient intakes of individuals.
• Tolerable Upper Intake Level (UL): Maximum daily intake unlikely to cause adverse health effects.

When the Food and Nutrition Board at the National Academies of Sciences, Engineering, and Medicine ⁷ evaluated the available data, it found the data insufficient to derive an EAR for pantothenic acid. Consequently, the Food and Nutrition Board at the National Academies of Sciences, Engineering, and Medicine established Adequate Intakes (AIs) for all ages based on usual pantothenic acid intakes in healthy populations ⁷. Table 1 lists the current Adequate Intakes (AIs) for pantothenic acid ⁷.

Table 1: Adequate Intakes (AIs) for Pantothenic Acid

Age	Male	Female	Pregnancy	Lactation
Birth to 6 months	1.8 mg	1.7 mg
7–12 months	1.8 mg	1.7 mg
1–3 years	2 mg	2 mg
4–8 years	3 mg	3 mg
9–13 years	4 mg	4 mg
14–18 years	5 mg	5 mg	6 mg	7 mg
19+ years	5 mg	5 mg	6 mg	7 mg

[Source ⁷]

Few data on pantothenic acid intakes in the United States are available. However, a typical mixed diet in the United States provides an estimated daily intake of about 6 mg, suggesting that most people in the United States consume adequate amounts ⁸. Some intake information is available from other Western populations. For example, a 1996–1997 study in New Brunswick, Canada, found average daily pantothenic acid intakes of 4.0 mg in women and 5.5 mg in men ⁹.

Sources of Pantothenic Acid

Food

Almost all plant- and animal-based foods contain pantothenic acid in varying amounts. Some of the richest dietary sources are beef, chicken, organ meats, whole grains, and some vegetables ¹⁰. Pantothenic acid is added to various foods, including some breakfast cereals and beverages (such as energy drinks) ¹⁰. Limited data indicate that the body absorbs 40%–61% (or half, on average) of pantothenic acid from foods ¹¹.

Edible animal and plant tissues contain relatively high concentrations of pantothenic acid. Food processing, however, can cause significant losses of this compound (20% to almost 80%) ¹².

Several food sources of pantothenic acid are listed in Table 2.

Table 2: Selected Food Sources of Pantothenic Acid

Food	Milligrams (mg) per serving	Percent DV*
Breakfast cereals, fortified with 100% of the DV	10	100
Beef liver, boiled, 3 ounces	8.3	83
Shitake mushrooms, cooked, ½ cup pieces	2.6	26
Sunflower seeds, ¼ cup	2.4	24
Chicken, breast meat, skinless, roasted, 3 ounces	1.3	13
Tuna, fresh, bluefin, cooked, 3 ounces	1.2	12
Avocados, raw, ½ avocado	1.0	10
Milk, 2% milkfat, 1 cup	0.9	9
Mushrooms, white, stir fried, ½ cup sliced	0.8	8
Potatoes, russet, flesh and skin, baked, 1 medium	0.7	7
Egg, hard boiled, 1 large	0.7	7
Greek yogurt, vanilla, nonfat, 5.3-ounce container	0.6	6
Ground beef, 85% lean meat, broiled, 3 ounces	0.6	6
Peanuts, roasted in oil, ¼ cup	0.5	5
Broccoli, boiled, ½ cup	0.5	5
Whole-wheat pita, 1 large	0.5	5
Chickpeas, canned, ½ cup	0.4	4
Rice, brown, medium grain, cooked, ½ cup	0.4	4
Oats, regular and quick, cooked with water, ½ cup	0.4	4
Cheese, cheddar, 1.5 ounces	0.2	2
Carrots, chopped, raw, ½ cup	0.2	2
Cabbage, boiled, ½ cup	0.1	1
Clementine, raw, 1 clementine	0.1	1
Tomatoes, raw, chopped or sliced, ½ cup	0.1	1
Cherry tomatoes, raw, ½ cup	0	0
Apple, raw, slices, ½ cup	0	0

Notes:

*DV = Daily Value. DVs were developed by the U.S. Food and Drug Administration (FDA) to help consumers compare the nutrient contents of products within the context of a total diet. The DV for the values in Table 2 is 10 mg for adults and children age 4 years and older. This value, however, decreases to 5 mg when the updated Nutrition and Supplement Facts labels are implemented ¹³. The updated labels must appear on food products and dietary supplements beginning in January 2020, but they can be used now ¹⁴. The FDA does not require food labels to list pantothenic acid content unless a food has been fortified with this nutrient. Foods providing 20% or more of the DV are considered to be high sources of a nutrient.

The U.S. Department of Agriculture’s (USDA’s) National Nutrient Database for Standard Reference ¹⁵ lists the nutrient content of many foods and provides a comprehensive list of foods containing pantothenic acid arranged by pantothenic acid content ¹⁶ and by food name ¹⁷.

[Source: United States Department of Agriculture Agricultural Research Service. ¹⁵]

A wide variety of plant and animal foods contain pantothenic acid ¹². About 85% of dietary pantothenic acid is in the form of coenzyme A (CoA) or phosphopantetheine ⁴. These forms are converted to pantothenic acid by digestive enzymes (nucleosidases, peptidases, and phosphorylases) in the intestinal lumen and intestinal cells. Pantothenic acid is absorbed in the intestine and delivered directly into the bloodstream by active transport (and possibly simple diffusion at higher doses) ⁴. Pantetheine, the dephosphorylated form of phosphopantetheine, however, is first taken up by intestinal cells and converted to pantothenic acid before being delivered into the bloodstream ¹⁸. The intestinal flora also produces pantothenic acid, but its contribution to the total amount of pantothenic acid that the body absorbs is not known ⁴. Red blood cells carry pantothenic acid throughout the body ⁴. Most pantothenic acid in tissues is in the form of CoA, but smaller amounts are present as acyl carrier protein or free pantothenic acid ⁴.

Pantothenic acid status is not routinely measured in healthy people. Microbiologic growth assays, animal bioassays, and radioimmunoassays can be used to measure pantothenic concentrations in blood, urine, and tissue, but urinary concentrations are the most reliable indicators because of their close relationship with dietary intake ¹². With a typical American diet, the urinary excretion rate for pantothenic acid is about 2.6 mg/day ¹⁹. Excretion of less than 1 mg pantothenic acid per day suggests deficiency ¹. Like urinary concentrations, whole-blood concentrations of pantothenic acid correlate with pantothenic acid intake, but measuring pantothenic acid in whole blood requires enzyme pretreatment to release free pantothenic acid from CoA ¹. Normal blood concentrations of pantothenic acid range from 1.6 to 2.7 mcmol/L, and blood concentrations below 1 mcmol/L are considered low and suggest deficiency ¹. Unlike whole-blood concentrations, plasma levels of pantothenic acid do not correlate well with changes in intake or status ¹.

Calcium pantothenate benefits

Pantothenic acid is important for our bodies to properly use carbohydrates, proteins, and lipids and for healthy skin.

Effective for pantothenic acid deficiency. Taking pantothenic acid by mouth prevents and treats pantothenic acid deficiency.

Possibly ineffective for skin reactions from radiation therapy. Applying dexpanthenol, a chemical similar to pantothenic acid, to areas of irritated skin does not seem to reduce skin reactions caused by radiation therapy.

Insufficient evidence to rate effectiveness for:

• Athletic performance. Some research suggests that taking pantothenic acid in combination with pantethine and thiamine does not improve muscular strength or endurance in well-trained athletes.
• Attention deficit-hyperactivity disorder (ADHD). There is conflicting evidence regarding the usefulness of pantothenic acid in combination with large doses of other vitamins for the treatment of ADHD.
• Constipation. Early research suggests that taking dexpanthenol, a chemical similar to pantothenic acid, by mouth daily or receiving dexpanthenol shots can help treat constipation.
• Eye trauma. Early research shows that applying drops containing dexpanthenol, a chemical similar to pantothenic acid, reduces eye pain and discomfort after surgery to the retinal. But applying dexpanthenol ointment doesn’t seem to help improve wound healing after surgery to the cornea.
• Osteoarthritis. Early research suggests that pantothenic acid (given as calcium pantothenate) does not reduce symptoms of osteoarthritis.
• Recovery of the bowels after surgery. Taking pantothenic acid or dexpanthenol, a chemical similar to pantothenic acid, does not seem to improve bowel function after gallbladder removal.
• Sore throat after surgery. Taking dexpanthenol, a chemical similar to pantothenic acid, by mouth might reduce sore throat symptoms after surgery.
• Rheumatoid arthritis. Early research suggests that pantothenic acid (given as calcium pantothenate) does not reduce the symptoms of arthritis in people with rheumatoid arthritis.
• Nasal dryness. Early research suggests that using a specific spray (Nasicur) that contains dexpanthenol, a chemical similar to pantothenic acid, helps relieve nasal dryness.
• Sinus infection. Early research suggests that using a nasal spray containing dexpanthenol, a chemical similar to pantothenic acid, after sinus surgery reduces discharge from the nose, but not other symptoms.
• Skin irritation. Applying dexpanthenol, a chemical similar to pantothenic acid, does not seem to prevent skin irritation caused by a certain chemical in soap. But it might help treat this type of skin irritation.
• Alcoholism.
• Allergies.
• Asthma.
• Carpal tunnel syndrome.
• Colitis.
• Convulsions.
• Dandruff.
• Diabetic problems.
• Enhancing immune function.
• Eye infections (conjunctivitis).
• Hair loss.
• Headache.
• Heart problems.
• Hyperactivity.
• Inability to sleep (insomnia).
• Irritability.
• Kidney disorders.
• Low blood pressure.
• Lung disorders.
• Multiple sclerosis.
• Muscle cramps.
• Muscular dystrophy.
• Other conditions.

More evidence is needed to rate the effectiveness of pantothenic acid for these uses.

Hyperlipidemia

Because of pantothenic acid’s role in triglyceride synthesis and lipoprotein metabolism, experts have hypothesized that pantothenic acid supplementation might reduce lipid levels in patients with hyperlipidemia ²⁰.

Several clinical trials have shown that the form of pantothenic acid known as pantethine reduces lipid levels when taken in large amounts ²¹, but pantothenic acid itself does not appear to have the same effects ¹. A 2005 review ²¹ included 28 small clinical trials (average sample size of 22 participants) that examined the effect of pantethine supplements (median daily dose of 900 mg for an average of 12.7 weeks) on serum lipid levels in a total of 646 adults with hyperlipidemia. On average, the supplements were associated with triglyceride declines of 14.2% at 1 month and 32.9% at 4 months. The corresponding declines in total cholesterol were 8.7% and 15.1%, and for low-density lipoprotein (LDL) “bad” cholesterol were 10.4% and 20.1%. The corresponding increases in high-density lipoprotein (HDL) “good” cholesterol were 6.1% and 8.4%.

A few additional clinical trials have assessed pantethine’s effects on lipid levels since the publication of the 2005 review. A double-blind trial in China ²² randomly assigned 216 adults with hypertriglyceridemia (204–576 mg/dl) to supplementation with 400 U/day CoA or 600 mg/day pantethine. All participants also received dietary counseling. Triglyceride levels dropped by a significant 16.5% with pantethine compared with baseline after 8 weeks. Concentrations of total cholesterol and non–HDL cholesterol also declined modestly but significantly from baseline. However, these declines might have been due, at least in part, to the dietary counseling that the participants received.

Two randomized, blinded, placebo-controlled studies by the same research group in a total of 152 adults with low to moderate cardiovascular disease risk found that 600 mg/day pantethine for 8 weeks followed by 900 mg/day for 8 weeks plus a therapeutic lifestyle change diet resulted in small but significant reductions in total cholesterol, LDL cholesterol, and non-HDL cholesterol compared with placebo after 16 weeks ²³, ²⁰. Increasing the amount of pantethine from 600 to 900 mg/day did not increase the magnitude of reduction in the lipid measures.

Additional studies are needed to determine whether pantethine supplementation has a beneficial effect on hyperlipidemia independently of, and together with, eating a heart-healthy diet. Research is also needed to determine the mechanisms of pantethine’s effects on lipid levels.

Pantothenic Acid Deficiency

Because some pantothenic acid is present in almost all foods, deficiency is rare except in people with severe malnutrition ¹². When someone has a pantothenic acid deficiency, it is usually accompanied by deficiencies in other nutrients, making it difficult to identify the effects that are specific to pantothenic acid deficiency ¹². The only individuals known to have developed pantothenic acid deficiency were fed diets containing virtually no pantothenic acid or were taking a pantothenic acid metabolic antagonist ²⁴.

On the basis of the experiences of prisoners of war in World War II and studies of diets lacking pantothenic acid in conjunction with administration of an antagonist of pantothenic acid metabolism, a deficiency is associated with numbness and burning of the hands and feet, headache, fatigue, irritability, restlessness, disturbed sleep, and gastrointestinal disturbances with anorexia ¹².

Groups at Risk of Pantothenic Acid Inadequacy

The following group is most likely to have inadequate pantothenic acid status.

People with a pantothenate kinase-associated neurodegeneration 2 mutation (PANK2)

Pantothenic acid kinase is an enzyme that is essential for CoA and phosphopantetheine production. It is the principle enzyme associated with the metabolic pathway that is responsible for CoA synthesis. Mutations in the pantothenate kinase 2 (PANK2) gene cause a rare, inherited disorder, pantothenate kinase-associated neurodegeneration (PKAN). PKAN is a type of neurodegeneration associated with brain iron accumulation ¹⁰. A large number of PANK2 mutations reduce the activity of pantothenate kinase 2, potentially decreasing the conversion of pantothenic acid to CoA and thus reducing CoA levels ⁵.

The manifestations of PKAN can include dystonia (contractions of opposing groups of muscles), spasticity, and pigmentary retinopathy ¹⁰. Its progression is rapid and leads to significant disability and loss of function ²⁵. Treatment focuses primarily on reducing symptoms ²⁶. Whether pantothenate supplementation is beneficial in PKAN is not known, but some anecdotal reports indicate that supplements can reduce symptoms in some patients with atypical PKAN ²⁷.

Calcium pantothenate side effects

Health risks from excessive pantothenic acid: the Food and Nutrition Board at the National Academies of Sciences, Engineering, and Medicine ⁷ was unable to establish Tolerable Upper Intake Levels (ULs) [Maximum daily intake unlikely to cause adverse health effects] for pantothenic acid because there are no reports of pantothenic acid toxicity in humans at high intakes. Some individuals taking large doses of pantothenic acid supplements (e.g., 10 g/day) develop mild diarrhea and gastrointestinal distress, but the mechanism for this effect is not known ²⁸.

Are there safety concerns?

Pantothenic acid is LIKELY SAFE for most people when taken by mouth in appropriate amounts. The recommended amount for adults is 5 mg per day. Even larger amounts (up to 10 grams) seem to be safe for some people. But taking larger amounts increases the chance of having side effects such as diarrhea.

Dexpanthenol, a derivative of pantothenic acid, is POSSIBLY SAFE when applied to the skin, used as a nasal spray, or injected as a shot into the muscle appropriately, short-term.

Special precautions and warnings

Pregnancy and breast-feeding: Pantothenic acid is LIKELY SAFE when taken by mouth in recommended amounts of 6 mg per day during pregnancy and 7 mg per day during breast-feeding. However, it is not known if taking more than this amount is safe. Avoid using larger amounts of pantothenic acid.

• Children:Dexpanthenol, a derivative of pantothenic acid, is POSSIBLY SAFE for children when applied to the skin.
• Hemophila: Do not take dexpanthenol, a derivative of pantothenic acid, if you have hemophila. It might increase the risk of bleeding.
• Stomach blockage: Do not receive injections of dexpanthenol, a derivative of pantothenic acid, if you have a gastrointestinal blockage.
• Ulcerative colitis: Use enemas containing dexpanthenol, a derivative of pantothenic acid, cautiously if you have ulcerative colitis.

Are there interactions with medications?

It is not known if this product interacts with any medicines.

Before taking this product, talk with your health professional if you take any medications.

Are there interactions with herbs and supplements?

• Royal jelly: Royal jelly contains significant amounts of pantothenic acid. The effects of taking royal jelly and pantothenic acid supplements together aren’t known.

Are there interactions with foods?

There are no known interactions with foods.

What dose is used?

The following doses have been studied in scientific research:

By MOUTH:

As a dietary supplement to prevent deficiency: 5-10 mg of pantothenic acid (vitamin B5).

Dietary Reference Intakes (DRI) are based on adequate intakes (AI) for pantothenic acid (vitamin B5) and are as follows: Infants 0-6 months, 1.7 mg; infants 7-12 months, 1.8 mg; children 1-3 years, 2 mg; children 4-8 years, 3 mg; children 9-13 years, 4 mg; men and women 14 years and older, 5 mg; pregnant women, 6 mg; and breastfeeding women, 7 mg.

What is d calcium pantothenate

Calcium D-pantothenate is also called calcium Dextro-Pantothenic acid, D-Pantothenic acid hemicalcium salt, Vitamin B5 or (R)-(+)-N-(2,4-Dihydroxy-3,3-dimethyl-1-oxobutyl)-β-alanine hemicalcium salt with chemical formula HOCH₂C(CH₃)₂CH(OH)CONHCH₂CH₂CO₂ ·1/2Ca ²⁹.

Figure 2. Calcium d pantothenate

References

1. Miller JW, Rucker RB. Pantothenic acid. In: Erdman JW, Macdonald IA, Zeisel SH, eds. Present Knowledge in Nutrition. 10th ed. Washington, DC: Wiley-Blackwell; 2012:375-90.
2. Voet, D., Voet, J.G., Pratt, C.W. (2006). Fundamentals of Biochemistry: Life at the Molecular Level, 2nd ed. Hoboken, NJ: John Wiley & Sons, Inc.
3. Gropper, S. S, Smith, J. L., Groff, J. L. (2009). Advanced nutrition and human metabolism. Belmont, CA: Wadsworth, Cengage learning.
4. Trumbo PR. Pantothenic acid. In: Ross AC, Caballero B, Cousins RJ, et al., eds. Modern Nutrition in Health and Disease. 11th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2014:351-7
5. Sweetman L. Pantothenic acid. In: Coates PM, Betz JM, Blackman MR, et al., eds. Encyclopedia of Dietary Supplements. 2nd ed. London and New York: Informa Healthcare; 2010:604-11
6. National Institutes of Health. Dietary Supplement Label Database. http://www.dsld.nlm.nih.gov/dsld/
7. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes: Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academy Press; 1998.
8. Iyenga GV, Wolfe WR, Tanner JT, et al. Content of minor and trace elements, and organic nutrients in representative mixed total diet composites from the USA. Sci Total Environ 2000;256:215-26 https://www.ncbi.nlm.nih.gov/pubmed/10902848
9. Provincial Epidemiology Service, New Brunswick Department of Health and Wellness. New Brunswick nutrition survey; 1997.
10. Trumbo PR. Pantothenic acid. In: Ross AC, Caballero B, Cousins RJ, et al., eds. Modern Nutrition in Health and Disease. 11th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2014:351-7.
11. Tarr JB, Tamura T, Stokstad EL. Availability of vitamin B6 and pantothenate in an average American diet in man. Am J Clin Nutr 1981;34:1328-37.
12. Miller JW, Rucker RB. Pantothenic acid. In: Erdman JW, Macdonald IA, Zeisel SH, eds. Present Knowledge in Nutrition. 10th ed. Washington, DC: Wiley-Blackwell; 2012:375-90
13. U.S. Food and Drug Administration. Food Labeling: Revision of the Nutrition and Supplement Facts Labels. https://www.federalregister.gov/documents/2016/05/27/2016-11867/food-labeling-revision-of-the-nutrition-and-supplement-facts-labels
14. U.S. Food and Drug Administration. Food Labeling: Revision of the Nutrition and Supplement Facts Labels and Serving Sizes of Foods That Can Reasonably Be Consumed at One Eating Occasion. https://www.federalregister.gov/documents/2017/10/02/2017-21019/food-labeling-revision-of-the-nutrition-and-supplement-facts-labels-and-serving-sizes-of-foods-that
15. U.S. Department of Agriculture, Agricultural Research Service. USDA Food Composition Databases. https://ndb.nal.usda.gov/ndb/
16. https://ndb.nal.usda.gov/ndb/nutrients/report/nutrientsfrm?max=25&offset=0&totCount=0&nutrient1=410&nutrient2=&nutrient3=&subset=0&sort=c&measureby=m
17. https://ndb.nal.usda.gov/ndb/nutrients/report/nutrientsfrm?max=25&offset=0&totCount=0&nutrient1=410&nutrient2=&nutrient3=&subset=0&sort=f&measureby=m
18. Sweetman L. Pantothenic acid. In: Coates PM, Betz JM, Blackman MR, et al., eds. Encyclopedia of Dietary Supplements. 2nd ed. London and New York: Informa Healthcare; 2010:604-11.
19. Tarr JB, Tamura T, Stokstad EL. Availability of vitamin B6 and pantothenate in an average American diet in man. Am J Clin Nutr 1981;34:1328-37 https://www.ncbi.nlm.nih.gov/pubmed/7258123
20. Rumberger JA, Napolitano J, Azumano I, et al. Pantethine, a derivative of vitamin B(5) used as a nutritional supplement, favorably alters low-density lipoprotein cholesterol metabolism in low- to moderate-cardiovascular risk North American subjects: a triple-blinded placebo and diet-controlled investigation. Nutr Res 2011;31:608-15 https://www.ncbi.nlm.nih.gov/pubmed/21925346
21. McRae MP. Treatment of hyperlipoproteinemia with pantethine: A review and analysis of efficacy and tolerability. Nutrition Research 2005;25:319-33.
22. Chen YQ, Zhao SP, Zhao YH. Efficacy and tolerability of coenzyme A vs pantethine for the treatment of patients with hyperlipidemia: A randomized, double-blind, multicenter study. J Clin Lipidol 2015;9:692-7 https://www.ncbi.nlm.nih.gov/pubmed/26350816
23. Evans M, Rumberger JA, Azumano I, et al. Pantethine, a derivative of vitamin B5, favorably alters total, LDL and non-HDL cholesterol in low to moderate cardiovascular risk subjects eligible for statin therapy: a triple-blinded placebo and diet-controlled investigation. Vasc Health Risk Manag 2014;10:89-100. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3942300/
24. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes: Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academy Press; 1998
25. Hayflick SJ. Defective pantothenate metabolism and neurodegeneration. Biochem Soc Trans 2014;42:1063-8 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5906047/
26. Gregory A, Hayflick SJ. Pantothenate Kinase-Associated Neurodegeneration. In: Adam MP, Ardinger HH, Pagon RA, et al., eds. GeneReviews. Seattle, WA: University of Washington, Seattle; 2017.
27. Kurian MA, Hayflick SJ. Pantothenate kinase-associated neurodegeneration (PKAN) and PLA2G6-associated neurodegeneration (PLAN): review of two major neurodegeneration with brain iron accumulation (NBIA) phenotypes. Int Rev Neurobiol 2013;110:49-71 https://www.ncbi.nlm.nih.gov/pubmed/24209433
28. Chawla J, Kvarnberg D. Hydrosoluble vitamins. Handb Clin Neurol 2014;120:891-914. https://www.ncbi.nlm.nih.gov/pubmed/24365359
29. Calcium D-pantothenate https://pubchem.ncbi.nlm.nih.gov/compound/25021359

Hexyl acetate in food

Hexyl acetate is an ester with the molecular formula C₈H₁₆O₂. Hexyl acetate is found in alcoholic beverages. Hexyl acetate is used in fruit essences and fruit aroma concentrates. Hexyl acetate is present in wines, black tea, soya bean and other food. Hexyl acetate, produces a characteristic apple, banana, grass, herb and pear aroma. Intake estimates USA ~ 160 µg/person per day and Europe ~ 3200 µg/person per day. The component hexyl alcohol is oxidized to hexanoic acid which is endogenous as an intermediary metabolite in the fatty acid pathway and acetate is a component of the tricarboxylic acid cycle. In the opinion of the Joint FAO/WHO Expert Committee on Food Additives (JECFA), the endogenous levels of these two metabolites would not give rise to perturbations outside the physiological range. Therefore, hexyl acetate was also determined to be of no safety concern based on its structural class and known metabolism ¹. No safety concern at current levels of intake when used as a flavoring agent ².

Hexyl acetate is mainly used as a solvent for resins, polymers, fats and oils. It is also used as a paint additive to improve its dispersion on a surface.

Hexyl acetate is a colorless liquid with a mild sweet odor. Flash point 113°F (45 °C). Hexyl acetate is a moderate fire risk. Inhalation of hexyl acetate is may cause adverse effects.

Hexyl acetate is insoluble in water and very soluble in alcohols and ethers. When heated to high temperatures emits acrid smoke and fumes. Used as a solvent and as a propellant in aerosols. Hexyl acetate has a boiling point of 334.4 to 338° F (168-170 °C) at 760 mm Hg and melting point of -112° F (−80 °C).

Figure 1. Hexyl acetate chemical structure

Toxicological data

• LD₅₀ oral rat. Lethal Dose 50% (LD₅₀) or median lethal dose is the amount of the substance required (usually per body weight) to kill 50% of the test population.
  Value: 36,100 mg/kg body weight ³
• LD₅₀ dermal rabbit. Value: > 5000 mg/kg body weight ⁴

Acute toxicity

The acute potential of hexyl acetate was examined in series of animal experiments. Since the results imply the typical active profile of alkyl acetates with comparable chain lengths, relevant general experiences with this substance group can be used as a supplement.

In a test on the eye-irritating potential on rabbit eyes, undiluted hexyl acetate (0.5 ml) triggered only minor irritations (irritation index 1 of max. 10). Labeling of the substance as eye-irritating proved to be unnecessary ⁵.

Undiluted hexyl acetate caused minor irritations (irritation index 3 of max. 10) in a trial on rabbit skin. Based on this finding hexyl acetate was classified as a weakly skin-irritating substance ⁵.

The skin-sensitizing potential was investigated in a test on probands (Repeat Insult Patch Test on 25 test persons) with 4% hexyl acetate in Vaseline. Skin reactions were not reported. Nor did a trial (Freund’s complete adjuvant test) of the ester on the skin of guinea pigs reveal any skin reactions. Although this test does not count among the standard methods, the result was considered sufficient to assess hexyl acetate as a non-skin irritating substance ⁵.

The dermal toxicity of the substance proved to be minor in older tests on rabbits. One of ten rabbits died after dermal application of undiluted hexyl acetate doses of 5,000 mg per kg of body weight; details were not provided ⁵. The other animals did not exhibit any toxicity symptoms during and after the exposure; the follow-up monitoring period amounted to 14 days. Other researchers did not observe any fatalities after the application of 20 ml per kg of body weight (approx. 17 g per kg of body weight) in a screening test on rabbits ⁵.

In humans, exposures to the vapors of alkyl acetates of comparable chain lengths (particularly the pentyl acetates) entailed chiefly irritations of the upper respiratory tract in humans, and, to a minor extent, eye irritations; exposures to very high concentrations also triggered CNS disorders (CNS-depressive effects) ⁵.

Corresponding effects are expected after exposure to hexyl acetate, but relevant data pertaining to the dose-response relation are scant:

An RD50 value determined for hexyl acetate in mice amounted to 740 ppm (The RD50 concentration is that concentration which reduces respiratory rate by 50%. RD50 gauge is used for measuring the sensory irritation: Decrease in the respiratory rate by 50%). It was determined that this concentration is not tolerable for humans due to the irritative effects on the eyes and the nose and throat region. Exposures to 74 ppm are expected to entail minor irritations ⁵. This assessment corresponds with the observation that 15-minute exposures to concentrations of 100 ppm of the isomer 1,3-dimethylbutyl acetate (sec-hexyl acetate) triggered irritations of the eyes and the upper respiratory tract in probands.

Systemic effects appear to occur only after exposures to much higher concentrations:

In a screening test rats tolerated 8-hour exposures to an atmosphere saturated with hexyl acetate vapors (approx. 1,450 ppm) without the occurrence of fatalities.
A more recent test available for the homologous 1PAcetate yielded similar results: Six-hour exposures to 3,000 ppm entailed neither toxicity symptoms nor the death of any rats.
In an animal experiment orally applied hexyl acetate proved to be almost non-toxic. Intragastral administration of the undiluted substance yielded an LD50 value of 41.5 ml per kg of body weight (approx. 36 g per kg of body weight). Symptoms or findings were not reported ⁵.
In humans the ingestion of large substance doses is expected to trigger irritations in the mouth and the throat as well as disorders of the CNS (depressive effects) ⁵.

Chronic toxicity

Specific experience reports on the industrial handling of the substance or results of long-term animal experiments are not available for hexyl acetate. Analogous to comparable alkyl acetates, repeated skin contact is expected to result in dehydration and chapped skin, followed by inflammations (dermatitis) ⁵.

Data from the industrial handling of pentyl acetates indicated that long-term exposures to very high vapour concentrations (> 3,500 ppm) triggered damage to the visual nerve in addition to pronounced eye irritations in individual exposed persons ⁵.

More recent long-term animal experiments with hexyl acetate homologues did not demonstrate any pronounced chronic systemic potential. Manufacturers refer to a series of subchronic inhalation studies performed with 1-butyl acetate in which rats had tolerated substance concentrations of 500 or 750 ppm ⁵.

A 13-week study performed with 1PA in which exposures of rats to concentrations of 600 or 1,200 ppm entailed decreased activities of the animals only in the first weeks appears to be of particular relevance. In the further development, exposures were tolerated without toxicity symptoms or other toxic effects. Nor did special tests on the neurotoxicity of the substance reveal corresponding dysfunctions in the animals; the dissection did not demonstrate changes in the nerve tissues ⁵.

With regard to the determination of work-place threshold values, it is assumed that irritative effects in the respiratory tract present the critical effect produced by the pentyl acetates. An analogous estimation is also available for the hexyl acetate isomer 1,3-dimethyl butyl acetate (sec-hexyl acetate) ⁵.

Reproductive toxicity, Mutagenicity and Carcinogenicity

Reproductive toxicity

Test results pertaining to hexyl acetate are not available ⁵. With regard to the developmental toxicity manufacturers refer to results of studies performed with 1-octyl acetate and 1-butyl acetate on rats that exhibited slight foetotoxic effects only after exposures to maternal toxic doses. In a study on rats n-hexanol, the hydrolysis product of hexyl acetate, triggered slight foetotoxic effects only after exposures to very high, maternal toxic doses. Suspicion of a specific developmental toxic potential of hexyl acetate could not be derived from these findings ⁵.

Relevant studies investigating the impact of the substance on fertility are not available ⁵.

Mutagenicity

The available information is insufficient ⁵. In a series of microbiological tests performed with hexyl acetate, 1 of 5 test systems yielded a positive result pointing to a mutagenic effect. However, this test result could not be reproduced in a later, analogous trial ⁵. Other in-vitro or in-vivo test results are lacking ⁵.

Carcinogenic potential

Information is not available ⁵.

Biotransformation and Excretion

Hexyl acetate is rapidly hydrolysed to 1-hexanol and acetic acid in the organism. In an in-vitro study on the metabolism of alkyl acetates (including hexyl acetate) performed with tissue preparations of nose, liver, lungs and trachea, the highest hydrolytic activities were found in the liver, followed by the nasal tissue. In acetates of straight-chain alcohols the hydrolyse process increased up to the pentyl residue but decreased with further increasing chain lengths. Hexyl acetate thus belongs to the very rapidly hydrolysed acetates, considerable portions of which are expected to be hydrolysed as early as in the respiratory tract ⁵. In the organism, hydrolytically generated 1-hexanol can be transformed to valeric acid via oxidation. Hexanoic acid, like the hydrolysis product acetic acid, is included in the physiological metabolism, since both metabolites are also formed endogenously ⁵.

Hexyl acetate uses

Hexyl acetate is present in wines, black tea, soya bean and other food. Hexyl acetate is used as a flavoring agent because it produces a characteristic apple, banana, grass, herb and pear aroma.

Hexyl acetate is mainly used as a solvent for resins, polymers, fats and oils. It is also used as a paint additive to improve its dispersion on a surface.

Hexyl acetate msds

References

1. Joint FAO/WHO Expert Committee on Food Additives (JECFA). WHO FOOD ADDITIVES SERIES 40. World Health Organization, Geneva 1998. http://www.inchem.org/documents/jecfa/jecmono/v040je14.htm
2. http://www.inchem.org/documents/jecfa/jeceval/jec_1044.htm
3. Toxicology and Applied Pharmacology. Vol. 28, Pg. 313, 1974
4. Food and Cosmetics Toxicology. Vol. 12, Pg. 913, 1974.
5. http://gestis-en.itrust.de/nxt/gateway.dll/gestis_en/570141.xml?f=templates$fn=default.htm$3.0

What is glycerol

Glycerol is also called glycerine or glycerin, is a trihydroxy sugar alcohol that is an intermediate in carbohydrate and lipid metabolism. Glycerol occurs naturally in several types of lipid and is an endogenous metabolite in mammals. Glycerol is rapidly and near completely absorbed from the gastrointestinal tract, it is then distributed into the total body water space and primarily metabolized in the liver. After phosphorylation and oxidation, glycerol is used as an energy substrate via glycolysis or participates in gluconeogenesis and lipogenesis. When the body uses stored fat as a source of energy, glycerol and fatty acids are released into the bloodstream. Circulating glycerol does not glycate proteins as do glucose or fructose, and does not lead to the formation of advanced glycation endproducts. Glycerol is extensively oxidized and exhaled as carbon dioxide, with only minor amounts excreted via urine or feces. Glycerol is a colorless, odorless, viscous liquid that is sweet-tasting and non-toxic. Glycerol (glycerin) is used as a solvent, emollient, humectant and vehicle in various pharmaceutical preparations, or sweetening agent in the food industry. As a sugar substitute, it has approximately 27 kilocalories per teaspoon (sugar has 20) and is 60% as sweet as sucrose. It does not feed the bacteria that form plaques and cause dental cavities. As a food additive, glycerol is labeled as E number E422. It is added to icing (frosting) to prevent it from setting too hard. Glycerol (glycerin) elevates the blood plasma osmolality thereby extracting water from tissues into interstitial fluid and plasma. Glycerol concentrations in blood higher than 92 mg/L would result in renal elimination of glycerol in rats and humans by preventing water reabsorption in the proximal tubule in the kidney leading to an increase in water and sodium excretion and a reduction in blood volume. Administered rectally, glycerol exerts a hyperosmotic laxative effect by attracting water into the rectum, thereby relieving constipation. In addition, glycerol (glycerin) is used as a solvent, humectant and vehicle in various pharmaceutical preparations.

In a subchronic toxicity study (in drinking water) in rats, the effects reported were observed with doses in the range of the oral median lethal dose (Lethal Dose 50% or LD50) values for glycerol. Lethal Dose 50% (LD50) or median lethal dose is the amount of the substance required (usually per body weight) to kill 50% of the test population The local irritating effects of glycerol in the gastrointestinal tract reported in some gavage studies in rat (100% glycerol at 2,800 mg/kg body weight (bw) per day, the lowest dose tested), and dogs (100% glycerol at 5,600 mg/kg body weight per day) was likely due to the hygroscopic and osmotic effects of large bolus doses of glycerol administered by gavage.

Glycerol did not show any genotoxic activity in a variety of in vitro assays. A lack of valid in vivo genotoxicity data was not of concern since clear negative findings were observed in in vitro assays. On this basis, the European Food Safety Authority (EFSA) Panel considered that glycerol as a food additive did not raise concern with respect to genotoxicity ¹.

From the available chronic toxicity and carcinogenicity studies, glycerol was not carcinogenic in mice and rats and did not show evidence of adverse effects in a 2‐year chronic toxicity study. The European Food Safety Authority (EFSA) Panel noted that no adverse effects were reported in rats receiving doses up to 10,000 mg/kg body weight per day for 1 year, the highest dose tested. The European Food Safety Authority (EFSA) Panel also noted that there was no increase in tumor incidences in rats receiving doses up to 5,000 mg/kg body weight per day for 2 years, the highest dose tested ².

The reports of the two and multigeneration reproductive toxicity studies have limitations but no adverse effects were reported. Prenatal developmental toxicity studies were also limited but showed no dose‐related developmental and maternal effects up to the highest dose tested (1,280, 1,600 or 1,180 mg glycerol/kg body weight per day for mice, rats and rabbits, respectively) ¹.

The European Food Safety Authority (EFSA) Panel considered that none of the animal studies available identified an adverse effect for glycerol ².

The European Food Safety Authority (EFSA) Panel considered that the therapeutic oral use of glycerol at 1,000–1,500 mg/kg body weight given as bolus in patients with glaucoma triggered an increase in plasma osmolality and dehydration and resulted in some patients with side effects such as headache, nausea and vomiting. Given the dose‐ and time period‐range reported in a study, the European Food Safety Authority (EFSA) Panel calculated that the minimum dose of glycerol required to induce a therapeutic reduction in intracranial pressures was within the range of 125–333 mg/kg body weight per hour. The European Food Safety Authority (EFSA) Panel considered that a conservative estimate of the lowest oral bolus dose of glycerol required for therapeutic effect was 125 mg/kg body weight per hour. The European Food Safety Authority (EFSA) Panel considered this dose would also be responsible for the side effects (nausea, headache and/or vomiting) observed in some patients.

The European Food Safety Authority (EFSA) Panel considered that the exposure estimates in all exposure scenarios resulted in overestimates of the exposure to glycerol from its use as a food additive according. Furthermore, the European Food Safety Authority (EFSA) Panel noted that the additional exposure to glycerol via natural sources, including wine and honey (the sources for which analytical data were available) did not significantly change the exposure to glycerol (E 422). The highest 95th percentile of exposure of glycerol and natural sources was estimated at 460 mg/kg body weight per day in children in the refined non‐brand‐loyal exposure scenario.

The European Food Safety Authority (EFSA) Panel considered that the most relevant situation where an acute bolus exposure to glycerol used as a food additive can be similar to the one occurring during therapeutic use is consumption of a beverage. Therefore, the European Food Safety Authority (EFSA) Panel calculated the volume of flavored drinks required to be consumed in order to exceed the acute bolus exposure (125 mg/kg body weight per hour) calculated by the European Food Safety Authority (EFSA) Panel to be the minimum dose required to have a therapeutic effect. When considering the available data, the European Food Safety Authority (EFSA) Panel noted that infants and toddlers can be exposed to more than 125 mg glycerol/kg body weight per hour by drinking less than the volume of one can (330 mL) of a flavored drink.

According to the conceptual framework for the risk assessment of certain food additives re‐evaluated under European Food Safety Authority (EFSA) Panel on Food Additives and Nutrient Sources added to Food 2014 and given that:

• the safety assessment carried out by the Panel is limited to the use and use levels received from industry and member states in 28 food categories out of 68 food categories in which glycerol is authorized;
• the highest 95th percentile of exposure of glycerol and natural sources was estimated at 460 mg/kg body weight per day in children in the refined non‐brand‐loyal exposure scenario;
• glycerol as a food additive is identical to a compound which is a normal constituent in the body (an endogenous compound) and is a regular component of the diet;
• sufficient toxicity data were available;
• the toxicological studies in animals did not provide any indication for adverse effects, including at the highest dose tested in a chronic toxicity study (10,000 mg/kg body weight per day);

The European Food Safety Authority (EFSA) Panel concluded that there is no need for a numerical Acceptable Daily Intake (ADI) for glycerol.

The European Food Safety Authority (EFSA) Panel concluded that there is no safety concern regarding the use of glycerol as a food additive for the general population at the refined exposure assessment for the reported uses of glycerol as a food additive ³.

However, the European Food Safety Authority (EFSA) Panel identified that there remain uncertainties over the lack of identification and quantification of residuals, especially those that are genotoxic and carcinogenic. The European Food Safety Authority (EFSA) Panel noted that these residuals are mostly present when chemical synthesis is used to produce glycerol. The European Food Safety Authority (EFSA) Panel concluded that the manufacturing process for glycerol should not allow the production of a food additive, which contains these residuals at a level, which would result in a margin of exposure (MOE) below 10,000.

The European Food Safety Authority (EFSA) Panel concluded that if 3‐monochloropropane‐1,2‐diol (3‐MCPD) is present at its maximum authorised level of 0.1 mg 3‐MCPD/kg glycerol, the maximum exposure to 3‐MCPD was below the tolerable daily intake (TDI) of 0.8 μg/kg body weight per day, and therefore exposure via glycerol alone was of no concern.

The European Food Safety Authority (EFSA) Panel could not calculate exposures to other genotoxic impurities or contaminants that may be present in glycerol as a result of the manufacturing process, e.g. glycidol, due to the lack of data on their concentrations in the food additive.

The European Food Safety Authority (EFSA) Panel concluded that infants and toddlers could be exposed to more than 125 mg/kg body weight per hour by drinking less than the volume of one can (330 mL) of a flavored drink. The European Food Safety Authority (EFSA) Panel further concluded that the acute bolus exposure to glycerol by its use as a food additive should stay below doses at which pharmacological or side effects could occur.

The European Food Safety Authority (EFSA) Panel recommended that:

• given that during the manufacturing processes of glycerol, genotoxic impurities – e.g. glycidol, epichlorohydrin – could be formed, limits for such impurities should be included in the specifications for glycerol (E 422);
• given that during the manufacturing processes of glycerol, other potential impurities of toxicological concern (e.g. dichlorohydrin) could be formed, limits for such impurities should be included in the specifications for glycerol (E 422);
• more data should be generated to decrease uncertainty arising from the presence in the food additive (E 422) of compounds of toxicological concern (e.g. acrolein, 3‐MCPD or 3‐MCPD ester), which can be produced under some food processing conditions (e.g. use of glycerol in parallel with lactic acid bacteria; use of glycerol in food containing significant amounts of sodium chloride (more than 5%) and treated at temperatures above 160°C, etc.);
• a numerical limit for acrolein should be included in the  specifications for glycerol ;
• the maximum limits for the impurities of toxic elements (arsenic, lead, mercury and cadmium) in the specification for glycerol should be revised in order to ensure that glycerol as a food additive will not be a significant source of exposure to those toxic elements in food;
• more information on uses and use levels and analytical data should be made available to the European Food Safety Authority (EFSA) Panel in order to perform an adequate exposure assessment, in particular in the case of estimate acute exposure, more data on flavored drinks is needed.

Glycerol chemical formula

Glycerol is described as a clear, colourless, hygroscopic syrupy liquid, with not more than a slight characteristic odor, which is neither harsh nor disagreeable. Glycerol is miscible in water and ethanol and immiscible in ether ⁴. The glycerol backbone is found in all lipids known as triglycerides. Glycerol has three hydroxyl groups that are responsible for its solubility in water and its hygroscopic nature (Figure 1).

Glycerol is generally obtained from plant and animal sources where it occurs as triglycerides. Triglycerides are esters of glycerol with long-chain carboxylic acids. The hydrolysis, saponification, or transesterification of these triglycerides produces glycerol as well as the fatty acid derivative.

Typical plant sources include soybeans or palm. Animal-derived tallow is another source.

Glycerol from triglycerides is produced on a large scale, but the crude product is of variable quality, with a low selling price of as low as 2-5 U.S. cents per kilogram in 2011 ⁵. Glycerol can be purified, but the process is expensive. Some glycerol is burned for energy, but its heat value is low.

Crude glycerol from the hydrolysis of triglycerides can be purified by treatment with activated carbon to remove organic impurities, alkali to remove unreacted glycerol esters, and ion exchange to remove salts. High purity glycerol (> 99.5%) is obtained by multi-step distillation; vacuum is helpful due to the high boiling point of glycerol (290 °C).

• Glycerol molecular weight is 92.094 g/mol
• Glycerol molar mass is 92.094 g/mol
• Glycerol melting point is 64.4 °F (18 °C)
• Glycerol boiling point is 554° F (290 °C) at 760 mm Hg
• Density of glycerol is 1.2613 g/cu cm at 68 °F (20 °C)

Figure 1. Glycerol molecule

 

 

Gycerol uses

Glycerol as an ingredient in food

The use of glycerol in beverages for athletes to enhance and maintain hydration status and to improve endurance exercise performance is described ⁶. Glycerol when used as a component of a hyperhydration strategy is prohibited by the World Anti‐Doping Agency (WADA) ⁷.

Pharmaceutical use

Glycerol is used in pharmaceutical products as an active ingredient as well as an excipient, e.g. solvent, plasticiser or lubricant ⁸. When glycerol is used as an excipient in medicinal products for oral administration and the glycerol intake is equal or above 10 g per single dose of the medicinal product, the information ‘May cause headache, stomach upset and diarrhea’ is required for the package leaflet ⁸. As an active ingredient, glycerol is used as an osmotic dehydrating agent. It is given orally, e.g. for the reduction in intra‐ocular pressure before and after ophthalmic surgery and as an adjunct in the management of acute glaucoma or to reduce intracranial pressure ⁸.

Glycerol has been used therapeutically by intravenously or oral administration to mobilize edema and to induce osmotic diuresis. Clinical experience and data from clinical studies are found in the literature indicating that doses up to 60,000 mg intravenously, infused over 1–4 hour, for a treatment duration of 1 week and in some studies, several weeks ⁹, and bolus oral doses (initial dose 1,500 mg/kg body weight, followed by 500–700 mg/kg body weight every 3 hour) ¹⁰ or 500–1,000 mg/kg body weight ¹¹.

The European Food Safety Authority (EFSA) Panel considered that the therapeutic administration of glycerol by oral administration to patients reported to be suffering disease that could impact significantly on their physiological functionality was not relevant in the safety assessment of glycerol as a food additive. However, glycerol has been prescribed for reduction in intraocular pressure in patients with glaucoma and may be prescribed prior to intraocular surgery ¹². For this indication, glycerol was reported to be administered orally as a bolus dose of 1,000–1,500 mg/kg body weight (as a 50% solution) with a daily total oral dose not higher than 120,000 mg (about 1,700 mg/kg body weight) ¹³. The European Food Safety Authority (EFSA) Panel considered that the therapeutic administration of glycerol by oral administration to patients reported to be suffering ocular disease – such as glaucoma and administration of glycerol to control participants in clinical studies – were relevant for the safety assessment of glycerol as a food additive.

The European Food Safety Authority (EFSA) Panel noted that for oral therapies to patients with ocular disease or healthy controls, glycerol was administered as a bolus at 1,350 mg/kg body weight ¹⁴; 1,500 mg/kg body weight ¹⁵; 1,500 mg/kg body weight ¹⁶; 1,000 mg/kg body weight ¹⁷; 1,000–1,270 mg/kg bw (McCurdy et al., 1966); 1,350 mg/kg body weight ¹⁸; 1,200 mg/kg body weight ¹⁹ and 1,260 mg/kg body weight ²⁰. The only side effects observed in these oral therapies to patients with ocular disease or healthy controls were either none or one or more of nausea, headache and/or vomiting.

Guidelines for glycerol use in hyperhydration and rehydration associated with exercise report 28 studies in which oral doses between 500 mg/kg body weight and 1,500 mg/kg body weight were given in the total of 238 subjects ²¹. Three studies reported side effects after rapidly administering the glycerol as a concentrated bolus followed by fluid ingestion. Four subjects in two of the trials were nauseous after glycerol ingestion. In another study, two subjects developed diarrhea in the 24 hours after the trial. In a further three studies, a low incidence of gastrointestinal distress (bloatedness) or light‐headedness were reported.

Using the studies of Wald and McLaurin ¹¹, the European Food Safety Authority (EFSA) Panel noted that patients were administered glycerol orally as bolus doses of 500–1,000 mg/kg body weight every 3–4 hour, dependent on the patients’ intracranial pressures (ICPs). Specific individual dosages ranged from 4,000 mg to 70,000 mg (average 54,000 mg) and it was administered via a nasogastric tube as a 50% solution (by mixing a 100% glycerol solution with an equal volume of either 5% dextrose in water or 5% dextrose in 0.4% normal saline, depending upon the systemic electrolyte status). If no change in intracranial pressure was achieved or a significant volume of solution was aspirated from the stomach, intravenous mannitol was administered and another trial of the drug was initiated 4–24 hour later. For the six patients in which data were reported in this study, maximum intracranial pressure reduction and maximum serum glycerol concentration occurred around 60–90 min after oral bolus ingestion. In most cases, the serum glycerol concentration returned to pre‐treatment levels around 3 hour after oral administration.

Given the dose‐ and time period‐range reported in this study, the European Food Safety Authority (EFSA) Panel calculated that the dose of glycerol required to induce a therapeutic reduction in intracranial pressure (ICP) was within the range of 125–333 mg/kg body weight per hour.

The European Food Safety Authority (EFSA) Panel therefore considered that a conservative estimate of the lowest oral bolus dose of glycerol required for therapeutic effect was 125 mg/kg body weight per hour. The European Food Safety Authority (EFSA) Panel considered this dose would also be responsible for the side effects (nausea, headache and/or vomiting) observed in some patients.

Glycerol therapy in diabetics

Hyperosmolar non‐ketotic coma occurred in diabetic patients after repeated use of oral and intravenous glycerol [e.g. Oakley and Ellis ²²; Sear ²³]. According to Sear ²³, the non‐ketotic hyperosmolar hyperglycaemic state usually occurs in cases of maturity onset diabetes or pre‐diabetes and not in non‐diabetic subjects.

Food industry

In food and beverages, glycerol serves as a humectant, solvent, and sweetener, and may help preserve foods. It is also used as filler in commercially prepared low-fat foods (e.g., cookies), and as a thickening agent in liqueurs. Glycerol and water are used to preserve certain types of plant leaves ²⁴.

As used in foods, glycerol is categorized by the Academy of Nutrition and Dietetics as a carbohydrate. The U.S. Food and Drug Administration (FDA) carbohydrate designation includes all caloric macronutrients excluding protein and fat. Glycerol has a caloric density similar to table sugar, but a lower glycemic index and different metabolic pathway within the body.

It is also recommended as an additive when using polyol sweeteners such as erythritol and xylitol which have a cooling effect, due to its heating effect in the mouth, if the cooling effect is not wanted.

Personal care applications

Glycerol is used in medical, pharmaceutical and personal care preparations, mainly as a means of improving smoothness, providing lubrication, and as a humectant. It is found in allergen immunotherapies, cough syrups, elixirs and expectorants, toothpaste, mouthwashes, skin care products, shaving cream, hair care products, soaps, and water-based personal lubricants. In solid dosage forms like tablets, glycerol is used as a tablet holding agent. For human consumption, glycerol is classified by the U.S. FDA among the sugar alcohols as a caloric macronutrient.

Glycerol is a component of glycerin soap. Essential oils are added for fragrance. This kind of soap is used by people with sensitive, easily irritated skin because it prevents skin dryness with its moisturizing properties. It draws moisture up through skin layers and slows or prevents excessive drying and evaporation.

Glycerol can be used as a laxative when introduced into the rectum in suppository or small-volume (2–10 ml) enema form; it irritates the anal mucosa and induces a hyperosmotic effect ²⁵.

Taken orally (often mixed with fruit juice to reduce its sweet taste), glycerol can cause a rapid, temporary decrease in the internal pressure of the eye. This can be useful for the initial emergency treatment of severely elevated eye pressure in glaucoma ²⁶.

Antifreeze

Like ethylene glycol and propylene glycol, glycerol is a non-ionic kosmotrope that forms strong hydrogen bonds with water molecules, competing with water-water hydrogen bonds. This interaction disrupts the formation of ice . The minimum freezing point temperature is about −36 °F (−38 °C) corresponding to 70% glycerol in water.

Glycerol was historically used as an anti-freeze for automotive applications before being replaced by ethylene glycol, which has a lower freezing point ²⁷. While the minimum freezing point of a glycerol-water mixture is higher than an ethylene glycol-water mixture, glycerol is not toxic and is being re-examined for use in automotive applications.

In the laboratory, glycerol is a common component of solvents for enzymatic reagents stored at temperatures below 0 °C due to the depression of the freezing temperature. It is also used as a cryoprotectant where the glycerol is dissolved in water to reduce damage by ice crystals to laboratory organisms that are stored in frozen solutions, such as bacteria, nematodes, and mammalian embryos.

Vibration dampening

Glycerol is used as fill for pressure gauges to dampen vibration ²⁸. External vibrations, from compressors, engines, pumps, etc., produce harmonic vibrations within Bourdon gauges that can cause the needle to move excessively, giving inaccurate readings. The excessive swinging of the needle can also damage internal gears or other components, causing premature wear. Glycerol, when poured into a gauge to replace the air space, reduces the harmonic vibrations that are transmitted to the needle, increasing the lifetime and reliability of the gauge.

Film industry

Glycerol is used by the film industry when filming scenes involving water to stop areas from drying out too quickly.

Glycerine is used—combined with water (around in a 1:99 proportion)—to create a smooth smoky environment. The solution is vaporized and pushed into the room with a ventilator.

References

1. Re‐evaluation of glycerol (E 422) as a food additive. https://efsa.onlinelibrary.wiley.com/doi/full/10.2903/j.efsa.2017.4720
2. Re‐evaluation of glycerol (E 422) as a food additive. EFSA Journal 2017;15(3):4720 https://efsa.onlinelibrary.wiley.com/doi/full/10.2903/j.efsa.2017.4720
3. Re‐evaluation of glycerol (E 422) as a food additive. EFSA Journal 2017;15(3):4720. https://efsa.onlinelibrary.wiley.com/doi/full/10.2903/j.efsa.2017.4720
4. JECFA (Joint FAO/WHO Expert Committee on Food Additives), 2006. Monograph 1. Combined compendium of food additive specifications.
5. Conversion of crude and pure glycerol into derivatives: A feasibility evaluation. Renewable and Sustainable Energy Reviews Volume 63, September 2016, Pages 533-555. https://www.sciencedirect.com/science/article/pii/S1364032116301666
6. Savoie FA, Asselin A and Goulet ED, 2016. Comparison of sodium chloride tablets–induced, sodium chloride solution–induced, and glycerol‐induced hyperhydration on fluid balance responses in healthy men. The Journal of Strength and Conditioning Research, 30, 2880–2891. https://www.ncbi.nlm.nih.gov/pubmed/26849790
7. WADA (World Anti‐Doping Agency), 2016. World Anti‐Doping Code, International Standard, https://www.wada-ama.org/sites/default/files/resources/files/wada-2016-prohibited-list-en.pdf
8. EMA (European Medicines Agency), 2003. Excipients in the label and package leaflet of medicinal products for human use, Guidelines Medicinal products for human use, Safety, environment and information, Vol. 3B. http://www.ema.europa.eu/docs/en_GB/document_library/Scientific_guideline/2009/09/WC500003412.pdf
9. Frank MSB, Nahata MC and Hilty MD, 1981. Glycerol: a review of its pharmacology, pharmacokinetics, adverse reactions and clinical use. Pharmacotherapy, 1, 147–160
10. Cantore G, Guidetti B and Virno M, 1964. Oral glycerol for the reduction of intracranial pressure. Journal of Neurosurgery, 21, 278–283.
11. Wald SL and McLaurin RL, 1982. Oral glycerol for the treatment of traumatic intracranial hypertension. Journal of Neurosurgery, 56, 323–331.
12. Bartlett JD, 1991. Adverse effects of anti‐glaucoma medications. Optometry Clinics, 1, 103–126. https://www.ncbi.nlm.nih.gov/pubmed/1686842
13. Gilman AG, 1990. Glycerol. Goodman and Gilman’s The pharmacological basis of therapeutics. 8th Edition. Pergamon Press, New York, 715 pp.
14. Buckell M and Walsh L, 1964. Effect of glycerol by mouth on raised intracranial pressure in man. The Lancet, 2, 1151–1152.
15. Drance SM, 1964. Effect of oral glycerol on intraocular pressure in normal and glaucomatous eyes. Archives of Ophthalmology, 72, 491–493. https://jamanetwork.com/journals/jamaophthalmology/article-abstract/627736
16. Consul BN and Kulsretha OP, 1965. Oral glycerol in glaucoma. American Journal of Ophthalmology, 60, 900–907.
17. Kornblueth W, Gombos G and Traud B, 1967. The effect of osmotic agents employed before cataract extraction. American Journal of Ophthalmology, 62, 220–222.
18. Charan H and Sarda RP, 1967. Glycerol in cataract surgery. American Journal of Ophthalmology, 63, 88–89
19. Krupin T, Kolker AE and Becker B, 1970. A comparison of isosorbide and glycerol for cataract surgery. American Journal of Ophthalmology, 69, 737–740
20. Friedman Z, Neumann E, Merksamer E and Garty J, 1980. Ocular hypotensive effect of oral glycerol in relation to blood osmolarity, glucose and electrolytes. Metabolic and Pediatric Ophthalmology, 4, 217–219.
21. Van Rosendal SP, Osborne MA, Fassett RG and Coomber JS, 2010. Guidelines for glycerol use in hyperhydration and rehydration associated with exercise. Sport Medicine, 40, 113–139. https://www.ncbi.nlm.nih.gov/pubmed/20092365
22. Oakley DE and Ellis PP, 1976. Glycerol and hyperosmolar nonketotic coma. American Journal of Ophthalmology, 81, 469–472
23. Sear ES, 1976. Nonkitotoc hyperosmolar hyperglycemia during glycerol therapy for cerebral edema. Neurology, 26, 89–94. https://www.ncbi.nlm.nih.gov/pubmed/942774
24. Gouin, Francis R. (1994). “Preserving flowers and leaves” (PDF). Maryland Cooperative Extension Fact Sheet. 556: 1–6. https://extension.umd.edu//sites/extension.umd.edu/files/_images/programs/hgic/Publications/non_HGIC_FS/FS556.pdf
25. https://www.drugs.com/cdi/glycerin-enema.html
26. https://www.mayoclinic.org/drugs-supplements/glycerin-oral-route/description/drg-20067747
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What is canthaxanthin

Canthaxanthin (β-β-carotene-4,4-dione) is a naturally occurring carotenoid pigment or keto-carotene which is synthesized by microorganisms and plants ¹. Canthaxanthin is one of the carotenoids without provitamin activity ². Canthaxanthin can be found in fruits, vegetables, and fish and primarily occurs in human tissue as a result of dietary ingestion. Like other carotenoids, it is fat-soluble and intensely colored. Canthaxanthin carries a red to orange hue and is used as an agent for coloring foods, dyes, and for skin bronzing. Experimental use has been successful for photoprotection for erythropoietic protoporphyria and cosmetic improvement in vitiligo ³. The bronzing effect is achieved through carotenoid deposition in the dermis and subcutaneous tissue. Past reports have concluded that this chemical canthaxanthin does not carry genotoxic, reproductive, or carcinogenic risks and does not have allergic potential as an oral medication and that acceptable daily intake is 0.03 mg/kg/day ⁴. However, there have been reports of adverse impacts on human health, mainly canthaxanthin retinopathy, which manifests as birefringent, yellow to red crystals in the macula ⁵. In addition, a case of aplastic anemia has been reported in association with canthaxanthin ingestion ⁶.

Both the Joint FAO/WHO Expert Committee on Food Additives (JECFA) and Scientific Committee on Food (SFC) committees have established an Acceptable Daily Intake (ADI) of 0.03 mg/kg body weight/day based on the formation of crystalline deposits in the retina (canthaxanthin retinopathy), which was observed in monkeys ⁷ and humans ⁸. The Acceptable Daily Intake (ADI) is defined as an estimate of the amount of a food additive, expressed on a body weight basis that can be ingested on a daily basis over a lifetime without appreciable risk to health. A no-observed-adverse-effect-level (NOAEL) of 0.25 mg/kg body weight/day for scotopic b-wave changes (without impairment of vision) was reported in a human study and a benchmark dose (BMD)05 of 12-20 mg/day, amounting to 0.20-0.33 mg/kg body weight/day for a 60 kg person, were derived in a worst case benchmark dose (BMD) analysis of the data from a meta-analysis on the crystal incidence in human eyes with increasing daily doses of canthaxanthin. Based on these two studies, the European Food Safety Authority (EFSA) Panel allocated an Acceptable Daily Intake (ADI) of 0.03 mg/kg body weight/day. This Acceptable Daily Intake (ADI) is in line with the ADI derived previously by JECFA and the SCF. The European Food Safety Authority (EFSA) Panel concluded that for both adults and children, total anticipated combined exposure to canthaxanthin from application as food and feed additive is unlikely to exceed the ADI.

The acute oral toxicity of canthaxanthin is very low. The oral Lethal Dose 50% (LD50) of canthaxanthin in mice is reported to be 10 000 mg/kg body weight. Lethal Dose 50% (LD50) is the amount of the substance required (usually per body weight) to kill 50% of the test population. In subchronic (13-week) studies with canthaxanthin, doses of 500 mg/kg body weight/day and higher in mice and of 2000 mg/kg body weight/day in rats were associated with small decreases in body weight compared with controls and discoloration of some internal tissues, but no toxicologically relevant changes were seen. From the few available in vitro and in vivo studies, there are no indications that canthaxanthin is genotoxic.

Canthaxanthin was not carcinogenic in doses amounting to 1000 mg/kg body weight/day in laboratory rodents. In two carcinogenicity studies in rats increased plasma cholesterol (especially in females) and increases in other clinical-chemistry parameters along with increased relative liver weights (females only) and histological changes in the liver were indicative of liver injury, but some of the changes were reversible after a recovery period. There were no indications that canthaxanthin had adverse effects on reproduction and/or the developing fetus in doses up to 1000 mg/kg body weight/day in rats and in doses up to 400 mg/kg body weight/day in rabbits.

There are no indications that canthaxanthin has an allergenic potential upon oral intake.

In animals, only 3 to 8% of orally administered canthaxanthin is absorbed and faecal excretion is the major route of elimination (85 to 89% of the dose in monkeys). Canthaxanthin is further distributed to liver, spleen, adipose tissue and adrenals. It is suggested by studies in rats that the amount of lipids ingested with the diet can increase the absorption of canthaxanthin. In monkeys, the concentration of canthaxanthin in the retina is dose-related, but nonlinear, suggesting that saturation could occur. In animals as well as in humans, elimination from adipose tissue is very slow, while canthaxanthin is eliminated from other tissues soon after withdrawal. In humans, a part of the orally ingested canthaxanthin is absorbed (9 to 34% of the dose) and its elimination is characterized by a long half-life of about 5 days. No data on canthaxanthin metabolism were reported in humans.

Figure 1. Canthaxanthin chemical structure

Canthaxanthin is also not generally considered a dietary carotenoid, but it may be included in the human diet by its widespread application as a coloring factor in foods and animal feeds ⁹, ¹⁰. In addition, Canthaxanthin has an antioxidant action, are free radical quenchers, potent quenchers of reactive oxygen species and nitrogen oxygen species, and chain-breaking antioxidants ¹¹. Canthaxanthin is a superior antioxidant and scavengers of free radicals when compared with the carotenoids such as β-carotene ¹². Canthaxanthin is documented to be able to suppress the development of preneoplastic liver cell lesions caused by aflatoxin B1 in rats by the deviation of aflatoxin B1 metabolism towards detoxification pathways ¹³.

Anti-cancer activity

Canthaxanthin may prevent proliferation of human colon cancer cells protect mouse embryo fibroblasts from transformation ¹⁴ and kept mice from mammary and skin tumor development ¹⁵. Canthaxanthin has also proved effective at preventing both oral and colon carcinogenesis in rats ¹⁶. Although it is a potent antioxidant, the chemopreventive impacts of canthaxanthin may also be associated to its ability to up-regulate gene expression, resulting in increased gap junctional cell-cell communication ¹⁷. There are evidences showing that the canthaxanthin is pure antioxidants because it shows little or no prooxidative behavior even at high carotenoid content and high oxygen tension ¹⁸. The chemopreventive effects of canthaxanthin may also be correlated to its ability to induce xenobiotic metabolizing enzymes, as has been shown in the liver, lungs and kidneys of rats ¹⁹. Canthaxanthin overuse as a sunless tanning product has caused to the appearance of crystalline deposits in the human retina ²⁰. There are some other studies showing induction of some enzymes by canthaxanthin. The group of researchers showed canthaxanthin induced P4501A1 and 1A2, and CYP1A1 and 1A2, which are involved in the metabolism of such potential carcinogens as polycyclic aromatic hydrocarbons, aromatic amines and aflatoxin ²¹. This xanthophyll also induced selected P450 enzymes in rat lung and kidney tissues, but not in the small intestine ²². On the basis of these studies, canthaxanthin shows inhibitory effects on cancer development in urinary bladder ²³, tongue ²⁴ and colorectum ²⁵ by the prevention of cell proliferation. Canthaxanthin has also showed cancer chemopreventive actions in UV-B-induced mouse skin tumorigenesis ²⁶ and chemically-induced gastric ²⁷ and breast carcinogenesis ²⁸. Canthaxanthin may inhibit the proliferation of human colon cancer cells and kept mouse embryo fibroblasts from transformation ¹⁴ and mice from mammary and skin tumor development ¹⁵. Canthaxanthin is efficient in preventing both oral and colon carcinogenesis in rats ²⁹.

Canthaxanthin retinopathy

In the setting of canthaxanthin retinopathy, it is thought that damage occurs at the level of the macular vascular system around areas of canthaxanthin-lipoprotein complex deposits, which comprise the visible crystals ³⁰. It is proposed that vascular dysfunction occurs due to aggregation of these complexes in vessel lipid layers, which modify and disrupt lipid membrane properties ³⁰.

Incidence and prevalence of canthaxanthin-induced retinopathy are difficult to predict due to the generally asymptomatic course of canthaxanthin retinopathy. Some reports state an incidence between 12 and 14% ³¹. Harnois et al. ³¹ noted that crystal appearance follows a dose-dependent correlation, seen with 50% of patients ingesting a total dose of 37 g and with 100% ingesting greater than 60 g.

To reproduce and investigate in a primate animal model the phenomenon of the red carotenoid canthaxanthin (beta, beta-carotene-4’4′-dione) to induce crystal-like retinal deposits as they have been observed in the ocular fundus of humans after high canthaxanthin intake (i.e., more than 30 mg/day), this study involving cynomolgus monkeys ⁷. The researchers found a high intake of canthaxanthin 5.4, 16.2, or 48.6 mg canthaxanthin/kg body weight daily orally for 2.5 years led to the deposition of crystal-like birefringent inclusions in the inner layers of the peripheral retina and, to some extent, the central retina of cynomolgus monkeys ⁷.

Several animal studies investigated ocular toxicity related to canthaxanthin deposition in the eye. The crystalline deposits were not observed in animals receiving 0.2 mg canthaxanthin/kg body weight/day. The canthaxanthin-induced retinal inclusions were not accompanied by adverse effects on visual function measured by electroretinography (ERG). In humans, a meta-analysis of the published studies and the available unpublished reports on crystal formation by Köpcke et al. ³² indicated a significant dose-response relationship for both total and daily doses of canthaxanthin. The incidence rates were, for the following daily doses (per subject), <30mg = 0%, 30 mg = 9.6%, 45 mg = 20.3%, 75-105 mg = 43.1%, > 105 mg = 52%. Crystal formation was reversible as evidenced by their disappearance albeit slowly over time in patients that had ceased high-dose consumption of canthaxanthin.

Funduscopic examination generally reveals highly reflective, tiny (30 μm) crystals accumulating in the perifoveal area. Daicker et al. ³³ reported that, when examined posthumously, light microscopy revealed birefringent crystals in the inner layers of the entire retina, and analysis with ultrahigh resolution optical coherence tomography (OCT) has shown that canthaxanthin retinopathy crystals are found in the outer plexiform layer ³⁴. While the vast majority of patients with canthaxanthin retinopathy remain asymptomatic, visual field defects, decreased visual acuity, abnormal electroretinogram testing, and low static luminance threshold may be present ³⁵. Decreased static perimetry testing in patients with canthaxanthin retinopathy compared to control group was described by Harnois et al. ³⁶, with a positive correlation with total drug dosage. On long-term followup, static perimetry testing returned to normal following discontinuation of the canthaxanthin. While often normal, fluorescein angiography may show a perifoveal ring of blocked fluorescence corresponding to areas of crystal deposition ⁸.

Treatment for canthaxanthin retinopathy is immediate discontinuation of the drug as soon as crystals are identified, even if the patient is asymptomatic ¹. Prognosis is very good with complete recovery occurring in the vast majority of patients. Hueber et al. ⁸ followed five patients for 16–24 years and no long-term adverse effects were found, and fluorescein angiography results were normal, although complete resolution of golden particle appearance took up to 20 years.

In summary, canthaxanthin retinal crystal deposition is a very common finding in patients with prolonged use of the canthaxanthin pills. Symptomatic visual loss is less common and correlates with total dosage and possibly patient age. Even with profound visual loss, prognosis for improvement is very good with recognition and discontinuation of the canthaxanthin drug ¹.

Figure 2. Canthaxanthin retinopathy

Note: Fundus photographs of a woman showing diffuse canthaxanthin crystal deposition. (A) Right eye. (B) Left eye.

[Source ¹]

Canthaxanthin tanning pills

According to the U.S. Food and Drug Administration (FDA) there are no such tanning pills approved for this purpose ³⁷. Nevertheless, pills bearing tanning claims continue to appear on the market. Consumers should be aware of risks associated with such products, as well as doubts about their efficacy.

Although canthaxanthin is approved by FDA for use as a color additive in foods, where it is used in small amounts, its use in so-called tanning pills is not approved ³⁷. Imported tanning pills containing canthaxanthin are subject to automatic detention as products containing unsafe color additives ³⁸.

The so-called tanning pills are promoted for tinting the skin by ingesting massive doses of color additives, usually canthaxanthin. When taken at these large doses – many times greater than the amount normally ingested in food – this substance is deposited in various parts of the body, including the skin, where it imparts a color. The color varies with each individual, ranging from orange to brownish. The bronzing effect is achieved through carotenoid deposition in the dermis and subcutaneous tissue. This coloration is not the result of an increase in the skin’s supply of melanin, melanin is the substance that is produced naturally in the skin to help protect it against UV radiation and gives skin its natural tan color.

Canthaxanthin side effects

Side effects of canthaxanthin pills include the deposition of crystals in the eye also known as “canthaxanthin-induced retinopathy” (see Figure 2 above). Hulisz and Boles ³⁹ also referred to reports of “nausea, cramping, diarrhea, severe itching, and welts” associated with the use of canthaxanthin “tanning” pills.

References

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20. Goralczyk R, Wu A, Goukassian D. Occurrence of birefringent retinal inclusions in cynomolgus monkeys after high doses of canthaxanthin. Invest Ophthalmol Vis Sci. 1997;38:741–52 https://www.ncbi.nlm.nih.gov/pubmed/9071228
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32. Köpcke W, Barker FM and Schalch W, 1995. Canthaxanthin-deposition in the retina. A biostatistical evaluation of 411 cases taking this carotenoid for medical or cosmetical purposes. Journal of Toxicology-Cutaneous and Ocular Toxicology 14, 89-104.
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What is citric acid

Citric acid (2-hydroxy-1,2,3-propane-tricarboxylic acid) is a weak organic acid found in the greatest amounts in citrus fruits, such as lemon, lime, grapefruit, tangerine, and orange ¹. Lemon and lime juices are rich sources of citric acid, containing 1.44 and 1.38 g/oz, respectively, comprising as much as 8% of the dry fruit weight ². The citric acid content of commercially available lemonade and other juice products varies widely, ranging from 0.03 to 0.22 g/oz. Citric acid is frequently used as a food additive as a natural preservative and also to add an acidic (sour) taste to foods and beverages ³. Citric acid is also a key intermediate in cellular metabolism, being a component of the tricarboxylic acid or Krebs cycle, citric acid is found in all human and animal tissues as an intermediary substance in oxidative metabolism. A major source of citric acid in your body results from endogenous metabolism in the mitochondria via the production of ATP in the citric acid cycle (see Citric acid cycle below).

Citric acid molar mass is 192.027 g/mol (anhydrous) and 210.14 g/mol (monohydrate) ⁴.

Figure 1. Citric acid formula (C₆H₈O₇)

[Source ⁵]

Is citric acid bad for you?

No. Citric acid occurs in all living organisms as an intermediate substance in oxidative metabolism in the tricarboxylic acid or Krebs cycle. A major source of citric acid in your body results from endogenous metabolism in the mitochondria via the production of ATP in the citric acid cycle (see Citric acid cycle below). Citric acid is a natural component of fruit, vegetables and plants (roots and leaves). Citric acid is found in significant quantities in lemon and lime juices (41 and 39 mg/kg for ready-to-consume juice and 31 and 30 mg/kg for concentrates, respectively). Levels of citric acid in commercial lemon juice-baseddrinks, such as lemonade, fall in the range of 0.62 to 0.96 mg/kg. Other dietary sources of citric acid include grapefruits and oranges (significant levels), berries and beans.

Citric acid (E330, anhydrous and monohydrate) is approved as a food additive ⁶ for general use in foodstuffs following the quantum satis principle (limits set for some food products, i.e. juices, infantfoods). It has a long history of use as an additive in food ⁷, cosmetics ⁸, pharmaceuticals (human and veterinary), plant protection products, biocides ⁹ and household cleaning products.
Citric acid has been assessed by the Joint FAO/WHO (Food and Agriculture Organization/World Health Organization) Experts Committee on Food Additives ⁸. The Committee allocated an acceptable daily intake (ADI) of ‘not limited’ for citric acid and its calcium, potassium and sodium salts. This position was retained by the Scientific Committee on Food (SCF) ¹⁰.

Furthermore, both the European Food Safety Authority (EFSA) ¹¹, ¹², ¹³ and U.S. Food and Drug Administration (FDA) has granted citric acid GRAS status (Generally Recognized as Safe) as an antioxidant, emulsifier, stabilizer and thickener in infant formula ¹⁴ and as an emulsifier in combination with lauramide ethyl ester in food in general, including meat and poultry ¹⁵.

Citric acid in food

Table 1. Citric Acid Content, in Descending Order, of Various Fruit Juices and Commercially-Available Juice Formulations (Grams per Liter)

Product	Type of product	Total citric acid Mean
Lemon juice	fresh, from fruit	48
Lime juice	fresh, from fruit	45.8
Lemon juice, Concord Foods	juice concentrate	39.2
Lime juice, ReaLime 100%	juice concentrate	35.4
Lemon juice, ReaLemon 100%	juice concentrate	34.1
Grapefruit juice, Florida’s Ruby Red	ready-to-consume	25
Orange juice, Tropicana Pure Premium	ready-to-consume	16.9
Orange juice, Tropicana Light ‘n Healthy	ready-to-consume	16.7
Orange juice	fresh, from fruit	9.1
Limeade/limonada, Minute Maid	ready-to-consume	7.3
Lemonade, Newman’s Own	ready-to-consume	6.7
Lemonade, Florida’s Natural	ready-to-consume	6.2
Lemonade, Minute Maid Light	ready-to-consume	5.2
Raspberry lemonade, Minute Maid	ready-to-consume	5
Lemonade, Tropicana	ready-to-consume	4.83
Pink lemonade, Minute Maid	ready-to-consume	4.8
Lemonade, Tropicana Sugar-Free	ready-to-consume	4.6
Lemonade, Minute Maid	ready-to-consume	4.4
Lemonade mix, Crystal Light	drink mix	4.2
Pink lemonade mix, Crystal Light	drink mix	3.4
Raspberry lemonade mix, Crystal Light	drink mix	3.1
Lemonade mix, Kool-Aid Sugarfree	drink mix	2.1
Lemonade mix, Country Time	drink mix	1.6
Crystallized lemon, True Lemon	dry mix	0.92

[Source ¹⁶]

Citric acid uses

Functional uses of citric acid as synergist for antioxidants, sequestrant, acidity regulator and flavoring agent ¹⁷. Citric acid is a preservative that more effective than acetic and lactic acids at inhibiting the growth of thermophilic bacteria ¹⁸. Citric acid is widely used in carbonated drinks and as an acidifier (reduce pH) of foods. It is less effective at controlling the growth of yeasts and mold than the other acids.

Citric acid (anhydrous and monohydrate) is approved as a food additive for use as a preservative in a wide range of commonly consumed foods and is authorized as a preservative in feed for all animal species without restrictions ¹⁹. “Citric acid is a normal constituent of the diet of humans and animals and, when ingested, is rapidly and completely metabolised to carbon dioxide and water; therefore, the use of citric acid in animal nutrition would not pose a risk to the environment”¹⁹.

Citric acid is used as an excipient in pharmaceutical preparations due to its antioxidant properties. Citrate salts of various metals are used to deliver minerals in biologically-available forms; examples include dietary supplements and medications. It maintains stability of active ingredients and is used as a preservative. Citric acid is also used as an acidulant to control pH.

Gastrointestinal absorption of citric acid from dietary sources has been associated with a modest increase in urinary citrate excretion ²⁰. The salts of citric acid (citrates) or anhydrous citric acid can be used as anticoagulants due to their calcium chelating ability in blood and as calcium kidney stones dissolution agent. The mechanism of action of anhydrous citric acid in calcium kidney stones dissolution agent is its acidifying activity and calcium chelating activity. Furthermore, knowledge of the citric acid content of beverages may be useful in nutrition therapy for calcium urolithiasis (formation of calcium kidney stones), especially among patients with hypocitraturia ¹⁶. Citrate is a naturally-occurring inhibitor of urinary crystallization; achieving therapeutic urinary citrate concentration is one clinical target in the medical management of calcium urolithiasis. When provided as fluids, beverages containing citric acid add to the total volume of urine, reducing its saturation of calcium and other crystals, and may enhance urinary citrate excretion.

Urinary citrate is a potent, naturally-occurring inhibitor of urinary crystallization ¹⁶. Citrate is freely filtered in the proximal tubule of the kidney. Approximately 10% to 35% of urinary citrate is excreted; the remainder is absorbed in various ways, depending on urine pH and other intra-renal factors. Citrate is the most abundant organic ion found in urine. Hypocitraturia, defined as <320 mg (1.67 mmol) urinary citrate/day ²¹, is a major risk factor for calcium urolithiasis. The activity of citrate is thought to be related to its concentration in urine, where it exhibits a dual action, opposing crystal formation by both thermodynamic and kinetic mechanisms. Citrate retards stone formation by inhibiting the calcium oxalate nucleation process and the growth of both calcium oxalate and calcium phosphate stones, largely by its ability to bind with urinary calcium and reduce the free calcium concentration, thereby reducing the supersaturation of urine. Citrate binds to the calcium oxalate crystal surface, inhibiting crystal growth and aggregation ²². There is also evidence that citrate blocks the adhesion of calcium oxalate monohydrate crystals to renal epithelial cells ²³. Medical interventions to increase urinary citrate are a primary focus in the medical management of urolithiasis ²⁴. The amount of diet-derived citrate that may escape in body conversion to bicarbonate is reportedly minor ²⁵. Nonetheless, a prior study reported increased urinary citrate after 1 week on 4 ounces lemon juice per day, diluted in 2 L water, in stone formers with hypocitraturia ²⁰. Two retrospective studies showed an effect in calcium stone formers of lemon juice and/or lemonade consumption on urinary citrate ²⁶, but a recent clinical trial showed no influence of lemonade on urinary citrate ²⁷.

Studies indicated that citrate decreases lipid peroxidation and downregulates inflammation by reducing polymorphonuclear cell degranulation and attenuating the release of myeloperoxidase, elastase, interleukin (IL)-1β, and platelet factor 4 ²⁸. In test tube study, citrate improved endothelial function by reducing the inflammatory markers and decreasing neutrophil diapedesis in hyperglycemia ²⁹. Moreover, citric acid has been shown to reduce hepatocellular injury evoked in rats by carbon tetrachloride ³⁰. Citric acid might thus prove of value in decreasing oxidative stress. Another animal study in mice ¹ suggests an antioxidant and anti-inflammatory effect for orally given citric acid at 1–2 g/kg in brain tissue, but this protective effect is lost when the dose is increased to 4 g/kg. Citric acid also demonstrated a beneficial hepatic protective effect at this dose range. Given that both increased brain oxidative stress and chronic inflammation have been linked to the development of neurodegenerative diseases, citric acid might thus prove of clinical benefit in such conditions.

Citric acid cycle

The citric acid cycle is the central metabolic hub of the cell, oxidizing carbon fuels, usually in the form of acetyl coenzyme A (acetyl CoA), as well as serving as a source of precursors for biosynthesis ³¹. The main function of the citric acid cycle is to transform fuel molecules into ATP. The citric acid cycle, in conjunction with oxidative phosphorylation, provides the vast majority of energy used by aerobic cells—in human beings, greater than 95%. The function of the citric acid cycle is the harvesting of high-energy electrons from carbon fuels. Note that the citric acid cycle itself neither generates a large amount of ATP nor includes oxygen as a reactant (Figure 5). Instead, the citric acid cycle removes electrons from acetyl CoA and uses these electrons to form NADH and FADH₂. In oxidative phosphorylation, electrons released in the reoxidation of NADH and FADH₂ flow through a series of membrane proteins (referred to as the electron-transport chain) to generate a proton gradient across the membrane. These protons then flow through ATP synthase to generate ATP from ADP and inorganic phosphate. Oxygen is required for the citric acid cycle indirectly inasmuch as it is the electron acceptor at the end of the electron-transport chain, necessary to regenerate NAD⁺ and FAD.

Citric acid cycle is highly efficient because a limited number of molecules can generate large amounts of NADH and FADH₂. Note in Figure 4 that the four-carbon molecule, oxaloacetate, that initiates the first step in the citric acid cycle is regenerated at the end of one passage through the cycle. The oxaloacetate acts catalytically: it participates in the oxidation of the acetyl group but is itself regenerated. Thus, one molecule of oxaloacetate is capable of participating in the oxidation of many acetyl molecules.

The overall pattern of the citric acid cycle is shown in Figure 4. A four- carbon compound (oxaloacetate) condenses with a two-carbon acetyl unit to yield a six-carbon tricarboxylic acid (citrate). An isomer of citrate is then oxidatively decarboxylated. The resulting five-carbon compound (α-ketoglutarate) also is oxidatively decarboxylated to yield a four-carbon compound (succinate). Oxaloacetate is then regenerated from succinate. Two carbon atoms enter the cycle as an acetyl unit and two carbon atoms leave the cycle in the form of two molecules of carbon dioxide. Three hydride ions (hence, six electrons) are transferred to three molecules of nicotinamide adenine dinucleotide (NAD⁺), whereas one pair of hydrogen atoms (hence, two electrons) is transferred to one molecule of flavin adenine dinucleotide (FAD).

The citric acid cycle is also an important source of precursors, not only for the storage forms of fuels, but also for the building blocks of many other molecules such as amino acids, nucleotide bases, cholesterol, and porphyrin (the organic component of heme). Recall that fuel molecules are carbon compounds that are capable of being oxidized—of losing electrons. The citric acid cycle includes a series of oxidation-reduction reactions that result in the oxidation of an acetyl group to two molecules of carbon dioxide. Citric acid cycle is the gateway to the aerobic metabolism of any molecule that can be transformed into an acetyl group or dicarboxylic acid.

The Link between Glycolysis and the Citric Acid Cycle

In human body cells, glycolysis (the breakdown of glucose) takes place in the cytoplasm of a cell. This pathway can be thought of as comprising three stages (Figure 2). Stage 1, which is the conversion of glucose into fructose 1,6-bisphosphate, consists of three steps: a phosphorylation, an isomerization, and a second phosphorylation reaction. The strategy of these initial steps in glycolysis is to trap the glucose in the cell and form a compound that can be readily cleaved into phosphorylated three-carbon units. Stage 2 is the cleavage of the fructose 1,6-bisphosphate into two three-carbon fragments. These resulting three-carbon units are readily interconvertible. In stage 3, ATP is harvested when the three-carbon fragments are oxidized to pyruvate.

From Figure 2, we know that glucose can be metabolized to pyruvate anaerobically to synthesize ATP through the glycolytic pathway. Glycolysis, however, harvests but a fraction of the ATP available from glucose. We now begin an exploration of the aerobic processing of glucose, which is the source of most of the ATP generated in metabolism.

The aerobic processing of glucose starts with the complete oxidation of glucose derivatives to carbon dioxide. This oxidation takes place in the citric acid cycle, a series of reactions also known as the tricarboxylic acid cycle or the Krebs cycle. The citric acid cycle is the final common pathway for the oxidation of fuel molecules—amino acids, fatty acids, and carbohydrates. Most fuel molecules enter the cycle as acetyl coenzyme A (acetyl CoA).

Under aerobic conditions, the pyruvate generated from glucose is oxidatively decarboxylated to form acetyl coenzyme A (acetyl CoA). In human cells, the reactions of the citric acid cycle take place inside mitochondria.

Figure 2. Glycolysis stages

Note: The glycolytic pathway can be divided into three stages: (1) glucose is trapped and destabilized; (2) two interconvertible three-carbon molecules are generated by cleavage of six-carbon fructose; and (3) ATP is generated.

[Source ³²]

The Formation of Acetyl Coenzyme A from Pyruvate

Pyruvate produced by glycolysis is converted into acetyl coenzyme A (acetyl CoA), the fuel of the citric acid cycle. Acetyl Coenzyme A (Acetyl CoA) is the fuel for the citric acid cycle. This important molecule is formed from the breakdown of glycogen (the storage form of glucose), fats, and many amino acids. The formation of acetyl coenzyme A (acetyl CoA) from carbohydrates is less direct than from fat. Carbohydrates, most notably glucose, are processed by glycolysis into pyruvate. Under anaerobic conditions, the pyruvate is converted into lactic acid or ethanol, depending on the organism. Under aerobic conditions, the pyruvate is transported into mitochondria in exchange for OH- by the pyruvate carrier, an antiporter. In the mitochondrial matrix, pyruvate is oxidatively decarboxylated by the pyruvate dehydrogenase complex to form acetyl coenzyme A (acetyl CoA).

This irreversible reaction is the link between glycolysis and the citric acid cycle (Figure 3). Note that, in the preparation of the glucose derivative pyruvate for the citric acid cycle, an oxidative decarboxylation takes place and high-transfer-potential electrons in the form of NADH are captured. Thus, the pyruvate dehydrogenase reaction has many of the key features of the reactions of the citric acid cycle itself.

Figure 3. The link between glycolysis and the citric acid cycle

Figure 4. Citric Acid Cycle

The citric acid cycle oxidizes two-carbon units, producing two molecules of CO₂, one molecule of Guanosine-5′-triphosphate (GTP), and high-energy electrons in the form of NADH and FADH₂.

Figure 5. Cellular Respiration

Control of the Citric Acid Cycle

The citric acid cycle is regulated primarily by the concentration of ATP and NADH. The key control points are the enzymes isocitrate dehydrogenase and α-ketoglutarate dehydrogenase.

Isocitrate dehydrogenase is allosterically stimulated by ADP, which enhances the enzyme’s affinity for substrates. The binding of isocitrate, NAD⁺, Mg²⁺, and ADP is mutually cooperative. In contrast, NADH inhibits iso-citrate dehydrogenase by directly displacing NAD⁺. ATP, too, is inhibitory. It is important to note that several steps in the cycle require NAD⁺ or FAD, which are abundant only when the energy charge is low.

A second control site in the citric acid cycle is α-ketoglutarate dehydrogenase. Some aspects of this enzyme’s control are like those of the pyruvate dehydrogenase complex, as might be expected from the homology of the two enzymes. α-Ketoglutarate dehydrogenase is inhibited by succinyl CoA and NADH, the products of the reaction that it catalyzes. In addition, α-ketoglutarate dehydrogenase is inhibited by a high energy charge. Thus, the rate of the cycle is reduced when the cell has a high level of ATP.

Figure 6. Control of the Citric Acid Cycle

References

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What is butylated hydroxytoluene

Butylated hydroxytoluene (2,6-Di-tert-butyl-4-methylphenol) also known as BHT or butylhydroxytoluene, is a synthetic α-tocopherol analogue antioxidant and preservative in the foods, cosmetics and pharmaceutical industry for scavenging hydrogen peroxide ¹. Butylated hydroxytoluene (BHT) is a white, crystalline solid which is odorless or has a faint aromatic odor. Butylated hydroxytoluene is insoluble in water, and freely soluble in ethanol and fatty oils. It has a melting point of 70 °C and an octanol/water partition coefficient of 5.1 ². According to the Hazardous Substances Data Bank HSDB ³, butylated hydroxytoluene (BHT) is prepared in a multistep process by the reaction of p-cresol (4-
methylphenol) with high purity isobutylene (2-methylpropene) using an acid catalyst. Upon neutralization by addition of sodium carbonate, crystallization with isopropanol, filtration and washing with isopropanol, the substance is dried and sieved to obtain the final product.

During storage, food quality is reduced quickly because of microbial spoilage and chemical reactions ⁴. The most important quality deterioration in the food systems is caused by chemical processes called lipid oxidation. In this process unsaturated fatty acids reacting with molecular oxygen via a free radical chain mechanism ⁵. As a consequence, hydroperoxides are formed which are unstable and decompose relatively quickly into aldehydes, ketones, alcohols, acids, esthers or hydrocarbons. These secondary oxidative products are responsible for food quality, nutrition, safety, color and consumers’ acceptance ⁶. The variables that affect the susceptibility of lipids to oxidation are temperature, fatty acid composition, antioxidants, metals, enzyme-catalyzed reactions, and water ⁷. In order to slow or control food’s lipid oxidation, manufacturers use antioxiative substances. The most commonly used are butyl hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tertiary-butyl hydroquinone (TBHQ), and propylgalate by directly adding them to food products ⁷.

Nowadays, active packaging which antioxidants are incorporated into packaging materials is an alternative way for food spoilage preservation ⁴. It can avoid contacting between the substances and the food as well as decrease the risk of adverse reactions ⁸. Active packaging extends the shelf life of food by preventing interacting of humidity or substances such as oxygen, ethylene, aroma or unusual flavors with the food ⁹. For example, incorporation of synthetic antioxidants, such as butylated hydroxytoluene (BHT) and butyl hydroxyanisole (BHA) in polyethylene film, showed to protect the fresh beef color from oxidation ¹⁰. However, in recent years, there has been a growing interest in the use of natural antioxidants in food packaging applications such as green tea extract with fish gelatin films ¹¹, brown algae extract with tuna-skin gelatin ¹², essential oil ¹³, tocopherols ¹⁴, catechin-lysozyme ¹⁵. Longan seeds and leaves have been employed as a good source of phenolic compounds, showing good antioxidant activity ¹⁶.

Figure 1. Butylated hydroxytoluene (BHT)

Butylated hydroxytoluene in food

Butylated hydroxytoluene (BHT) is a synthetic antioxidant authorized for use in fats and oils, only for the professional manufacture of heat-treated food, in frying oil and frying fat (excluding olive pomace oil) and in lard, fish oil, beef, poultry and sheep fat ¹⁷. Butylated hydroxytoluene (BHT) is permitted alone or in combination with other antioxidants such as gallates, tert-butylhydroquinone (TBHQ) and butylated hydroxyanisole (BHA) in amounts up
to 100 mg/kg expressed as fat. In addition, butylated hydroxytoluene (BHT) is permitted in chewing gum alone or in combination with the aforementioned antioxidants at a maximum level of 400 mg/kg chewing gum ¹⁷.

No data on the actual levels of butylated hydroxytoluene (BHT) in foods have been found during literature searches in the databases ToxNet, PubMed and CAPlus, or on the web pages of the Food Standards Agency of Great Britain. The Danish Veterinary and Food Administration has reported a project on monitoring and control of food additives in which butylated hydroxytoluene (BHT) levels were analyzed in 122 samples of emulsified and non-emulsified sauces (dressings, ketchup etc.) and fruit- and vegetable preparations (chutney, tomato paste etc.). Butylated hydroxytoluene (BHT) was not identified in any of these samples ¹⁸.

When scrutinizing ingredient lists on various chewing gums on the Danish market, butylated hydroxytoluene (BHT) is not mentioned in the list of ingredients on every brand. Hence, it can be deduced that chewing gum may be manufactured without the use of butylated hydroxytoluene (BHT). In a survey by Bemrah et al. ¹⁹ 1 out of 28 chewing gum brands was found to contain 200 mg butylated hydroxytoluene/kg, whereas the remainder contained no butylated hydroxytoluene (BHT).

Additional information on reported use levels of use for butylated hydroxytoluene was made available to the Panel by FoodDrinkEurope. For the food categories “fats and oils for the professional manufacture of heat-treated foodstuffs” and for “lard, fish oil, beef, poultry and sheep fat” the data made available are listed in Table 1. For other food categories where the use of butylated hydroxytoluene is authorized, FoodDrinkEurope either reported that no data were received from their membership or that these categories are not representatively covered by FoodDrinkEurope’s membership. Butylated hydroxytoluene (BHT) is also used in food contact materials with a specific migration limit of 3 mg/kg food (Commission Regulation 10/201111).

Table 1. Maximum Permitted Levels of butylated hydroxytoluene (BHT) in foodstuffs according to Directive No 95/2/EC and maximum reported use levels of BHT in foodstuffs used for the refined exposure assessment

[Source ¹⁷]

Table 2. Summary of anticipated exposure to butylated hydroxytoluene (BHT) from its use as food additive using maximum reported use levels for four population groups

[Source ¹⁷]

Table 2 summarizes the estimated exposure to butylated hydroxytoluene (BHT) from its use as food additive of all four population groups. An exposure to butylated hydroxytoluene from the consumption of chewing gum using the Maximum Permitted Level for this food category of 400 mg/kg would require a daily intake of 7.5 g of chewing gum to reach a level of 0.05 mg butylated hydroxytoluene (BHT)/kg body weight/day. Unfortunately, very limited data were available for the consumption of this food category in the Comprehensive Database since only few consumers in some countries reported data on chewing gum consumption. It also has to be considered that not all butylated hydroxytoluene (BHT) present in chewing gum will be ingested. It was concluded that 80-99% of butylated hydroxytoluene (BHT) in chewing gum is not ingested ²⁰, but ingestion may be higher given that higher levels of extraction of up to 50% were also found in one study ²¹. Assuming a 10% extraction and subsequent ingestion of butylated hydroxytoluene (BHT) from chewing gum and selecting only those surveys with a sufficiently high number of consumers, the average exposure to butylated hydroxytoluene (BHT) from chewing gum consumption is in the range of 0-0.003 mg/kg body weight/day for children, 0-0.002 mg/kg body weight/day for adolescents and 0-0.004 mg/kg body weight/day for adults (consumers only). At the 95th percentile, exposure to butylated hydroxytoluene (BHT) from chewing gum consumption is in the range of 0.004-0.008 mg/kg body weight/day for children, 0.003-0.006 mg/kg bw/day for adolescents and 0.004-0.008 mg/kg body weight/day for adults.

Using a worst case scenario of combined exposure to butylated hydroxytoluene (BHT) from food categories where its use as food additive is authorized, the European Food Safety Authority (EFSA) Panel estimated potential exposure to be in the range of 0.01-0.03 mg/kg body weight/day on average and 0.03-0.17 mg/kg body weight/day at the 95th percentile for adults. For adolescents, combined exposure to butylated hydroxytoluene (BHT) from all food categories would be on average in the range of 0.01-0.05 mg/kg body weight/day and in the range of 0.04-0.13 mg/kg body weight/day at the 95th percentile. For children, combined exposure to butylated hydroxytoluene (BHT) from all food categories would be on average in the range of 0.01-0.09 mg/kg body weight/day and in the range of 0.05-0.30 mg/kg body weight/day at the 95th percentile. Exposure to butylated hydroxytoluene (BHT) from its use in food contact materials with a specific migration limit of 3 mg/kg food and the assumption that every day throughout lifetime a person weighing 60 kg consumes 1 kg of food packed in plastics containing butylated hydroxytoluene (BHT) in the maximum permitted quantity would be increased by 0.05 mg/kg body weight/day. Assuming that children weighing 15 kg also consume 1 kg of food packed in plastics containing butylated hydroxytoluene (BHT) in the maximum permitted quantity, exposure to butylated hydroxytoluene (BHT) of children would be increased by 0.2 mg/kg body weight/day.

The European Union Scientific Committee for Food (SCF) established an Acceptable Daily Intake (ADI) for butylated hydroxytoluene (BHT) of 0-0.05 mg/kg body weight/day based on thyroid, reproduction and hematological effects in the rat. Acceptable Daily Intake (ADI) is an estimate of the amount of a food additive that can be ingested daily over a lifetime without appreciable health risk. The Joint FAO/WHO Expert Committee on Food Additives (JECFA) allocated an ADI of 0-0.3 mg/kg body weight/day for butylated hydroxytoluene (BHT) based on effects in the reproduction segments and hepatic enzyme induction seen in two separate 2-generation studies in rats. The European Food Safety Authority (EFSA) Panel concluded that butylated hydroxytoluene (BHT) is not of concern with respect to genotoxicity and that any carcinogenicity would be thresholded. After the last European Union Scientific Committee for Food (SCF) evaluation, two new 2-generation studies have been reported which were the basis for the ADI set by Joint FAO/WHO Expert Committee on Food Additives (JECFA). Both studies revealed a No-observed-adverse-effect level (NOAEL) of 25 mg/kg body weight/day. No-observed-adverse-effect level (NOAEL) is the greatest concentration or amount of a substance, found by experiment or observation, that causes no detectable adverse alteration of morphology, functional capacity, growth, development, or lifespan of the target organism under defined conditions of exposure. Overall, the European Food Safety Authority (EFSA) Panel concluded that the present database gives reason to revise the ADI of 0.05 mg/kg body weight/day. Based on the NOAEL of 25 mg/kg body weight/day and an uncertainty factor of 100, the European Food Safety Authority (EFSA) Panel derived an ADI of 0.25 mg/kg body weight/day. Since the NOAEL of 25 mg/kg body weight/day is below the BMDL10 value of 247 mg/kg body weight/day derived from the data for the incidence of hepatocellular carcinomas (liver cancers) in male rats, the European Food Safety Authority (EFSA) Panel concluded that this NOAEL also covers the hepatocellular carcinomas observed in the long-term studies with butylated hydroxytoluene (BHT). Exposure of adults to butylated hydroxytoluene (BHT) is unlikely to exceed the newly derived Acceptable Daily Intake (ADI) at the mean and at the 95th percentile. Benchmark dose (BMD) is defined as the dose that corresponds to a specific change in an adverse response compared to the response in unexposed subjects and the lower 95% confidence limit is termed the benchmark dose level (BMDL). For exposure of children to butylated hydroxytoluene (BHT) from its use as food additive, the European Food Safety Authority (EFSA) Panel noted that it is also unlikely that this ADI is exceeded at the mean, but is exceeded for some European countries (Finland, The Netherlands) at the 95th percentile.

Butylated hydroxytoluene biological and toxicological data

In one study in humans the urinary metabolites butylated hydroxytoluene (BHT)-COOH (the “acid”) and benzoyl-glycine (hippuric acid) were found after two separate oral doses of 100 mg butylated hydroxytoluene (BHT), and in another study butylated hydroxytoluene (BHT)-COOH and its glucuronide ester were the only major metabolites identified in urine after an oral dose of 1.0 g ²². In two men, excretion of a single oral dose of 40 mg/kg [14C] butylated hydroxytoluene (BHT) was 50% in the first 24 hours, followed by slower excretion for the next 10 days. In total, 63-67% of the dose was excreted in the urine after 10 days. Fecal excretion was measured in one man and was found to be 0.3% of the dose per day initially, and waning off to 0.02% of the dose per day, 31 days after dosing ²³.These studies show that butylated hydroxytoluene (BHT) is rapidly absorbed from the gastrointestinal tract and distributed. Upon absorption, butylated hydroxytoluene (BHT) is generally distributed to the liver and body fat. Excretion is mainly via urine and feces. The metabolism of butylated hydroxytoluene (BHT) is complex. There may be important species differences. It is not known for example whether humans are capable of forming the quinone methides, metabolites that were found in rats and mice. In addition, biliary excretion seems not to be as significant in man as it is in rats, rabbits and dogs.

Acute oral toxicity

According to the results of acute toxicity studies with butylated hydroxytoluene (BHT) reported to JECFA ²², butylated hydroxytoluene (BHT) possesses low acute toxicity. The acute oral LD50 of butylated hydroxytoluene (BHT) was 1700-1970 mg BHT/kg body weight in rats, 2100-3200 mg butylated hydroxytoluene (BHT)/kg body weight in rabbits, 10,700 mg BHT/kg body weight in guinea pigs, 940-2100 mg BHT/kg body weight in cats, and 2000 mg BHT/kg bw in mice ²⁴.

Short-term or subchronic exposure to butylated hydroxytoluene  (BHT) affects the liver of mice, rats and chickens, also showing histopathological changes in this organ. In addition, BHT has been shown to increase the relative thyroid and adrenal weight in rats. Newer data show an α-tocopherol sparing effect in rats.None of the studies available could be used to derive a No-observed-adverse-effect level (NOAEL).

Genotoxicity

The genotoxicity of butylated hydroxytoluene (BHT) has been studied in several in vitro systems ²² and an extensive database of genotoxicity studies for butylated hydroxytoluene (BHT) was reviewed by Bomhard et al. ²⁵ and by Williams et al. ²⁶. These authors concluded that the majority of evidence indicated a lack of potential for butylated hydroxytoluene (BHT) to induce point mutations, chromosomal aberrations, or to interact with or damage DNA, and that butylated hydroxytoluene (BHT) does not represent a genotoxic risk.

TemaNord ² reported that butylated hydroxytoluene (BHT) was not genotoxic in vivo in rats at oral doses up to 500 mg/kg body weight (dominant lethal assay) or in mice at doses of 1% in the feed (approximately 1000 mg/kg body weight/day) (dominant lethal and heritable translocation assays).

In general, the genotoxicity studies on butylated hydroxytoluene (BHT) show that the majority of evidence indicates a lack of potential for butylated hydroxytoluene (BHT) to induce point mutations, chromosomal aberrations, or to interact with or damage DNA. The European Food Safety Authority (EFSA) Panel recognized that positive genotoxicity results obtained in vitro with butylated hydroxytoluene (BHT) and butylated hydroxytoluene (BHT) metabolites may be due to pro-oxidative chemistry giving rise to formation of quinones and reactive oxygen species and that such a mechanism of genotoxicity is generally considered to have a threshold.

The International Agency for Research on Cancer ²⁷ evaluated butylated hydroxytoluene (BHT) and classified it in group 3, since no evaluation could be made of the carcinogenicity of butylated hydroxytoluene (BHT) to humans, and there was
limited evidence for the carcinogenicity in experimental animals. Williams et al. ²⁶ have reviewed data on genotoxicity and carcinogenicity of butylated hydroxytoluene (BHT) including reports which appeared subsequent to the International Agency for Research on Cancer ²⁷ evaluation. Williams et al. ²⁶ argued that butylated hydroxytoluene (BHT) is not genotoxic or carcinogenic; they particularly argued that the carcinogenicity in rats found in the study by Olsen et al. ²⁸ has not been confirmed in other studies with rats, and that the effects found may be attributable to study conditions and not to the administration of butylated hydroxytoluene (BHT). They also point out that a more recent study ²⁹ dosing Wistar rats for up to 18 months with 0.1% 2,2’-methylenebis (4-methyl-6-tertbutylphenol), an antioxidant which is essentially two molecules of butylated hydroxytoluene (BHT) and has all the attributes of butylated hydroxytoluene (BHT), did not result in a carcinogenic response.

The European Food Safety Authority (EFSA) Panel concluded that butylated hydroxytoluene (BHT) in high doses can exert tumor-promoting effects in some animal models. The data do not allow the establishment of a NOAEL for a carcinogen-promotional effect.

The association between dietary intake of butylated hydroxytoluene (BHT) and stomach cancer risk was investigated in the Netherlands Cohort Study (NLCS) that started in 1986 among 120 852 men and women aged 55-69 years. A semi-quantitative food frequency questionnaire was used to assess food consumption.
Information on butylated hydroxytoluene (BHT) content of cooking fats, oils, mayonnaise and other creamy salad dressings and dried soups was obtained by chemical analysis, a Dutch database of food additives (ALBA) and the Dutch Compendium of Foods and Diet Products. After 6.3 years of follow-up, complete data on butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) intake of 192 incident stomach cancer cases and 2035 sub-cohort members were available for case-cohort analysis. Mean intake of butylated hydroxytoluene (BHT) among sub-cohort members was 0.351 mg/day. No association with stomach cancer risk was observed for consumption of mayonnaise and other creamy salad dressings with butylated hydroxytoluene (BHT). A statistically non-significant decrease in stomach cancer risk was observed with increasing BHA and butylated hydroxytoluene (BHT) intake. No significant association with stomach cancer risk was found in this study, for normal dietary intake of low levels of butylated hydroxytoluene (BHT) ³⁰.

In conclusion, lung or liver tumors have been seen in some studies in mice or rats exposed orally to butylated hydroxytoluene (BHT) as the single test substance. BMD analyses of the data reported by Brooks et al. ³¹ on the incidence of lung neoplasia in mice induced by butylated hydroxytoluene (BHT) revealed a BMDL10 of 38 mg/kg body weight/day, and of the data reported by Olsen et al. ²⁸ on the incidence of hepatocellular carcinomas in male rats induced by butylated hydroxytoluene (BHT) a BMDL10 of 247 mg/kg body weight/day. The NOAEL for non-neoplastic effects in the study of Olsen et al. ²⁸ was 25 mg/kg bw/day, based on the effects on litter size, sex ratio and pup body weight gain during the lactation period in the reproduction segment of the study.

Reproductive and developmental toxicity

Studies on reproductive toxicity have been reported in mice, rats, chickens and monkeys ²². In a study by Eriksson and Siman ³², pregnant diabetic and normal Sprague-Dawley rats were fed as required either a standard diet or a diet with 1% of butylated hydroxytoluene (BHT) (estimated to be equivalent to approximately 500 mg/kg body weight/day). The fetuses of the diabetic rats (2.70 g body weight) were smaller than the fetuses of the normal rats (3.68 g) when the mothers were fed a standard diet. The butylated hydroxytoluene (BHT) diet increased the fetal weight in the offspring of diabetic rats (3.17 g), with no change in fetuses of the normal rats (3.65 g). The placentas of diabetic rats were heavier than the placentas of normal rats; this difference was not present in the butylated hydroxytoluene (BHT)-fed rats. The butylated hydroxytoluene (BHT) treatment had no effect on the rate of resorptions, which was increased in the diabetic rats compared with the normal rats. In contrast, the increased rate of congenital malformations in the offspring of diabetic rats (19%), compared with that in the normal rats (0%), was markedly decreased by the butylated hydroxytoluene (BHT) diet (2.3%). No malformations were found in the normal rats treated with butylated hydroxytoluene (BHT). The European Food Safety Authority (EFSA) Panel considered that the only dose level of butylated hydroxytoluene (BHT) tested in this study of 500 mg/kg body weight/day can be considered a NOAEL.

Hypersensitivity, allergy and intolerance

Two patients with chronic idiopathic urticaria were subjected to double-blind, placebo-controlled, oral challenges with a series of food additives. During testing, butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA) were identified as causative agents. Avoidance of foods containing butylated hydroxytoluene (BHT) and BHA resulted in long-term reduction in severity and frequency of urticarial episodes ³³.

In a double-blind placebo controlled study by Hannuksela and Lahti ³⁴ with challenge tests of 44 patients with chronic urticaria, 91 with atopic dermatitis and 123 with contact dermatitis, none reacted to butylated hydroxytoluene (BHT) when it was ingested in a capsule containing 50 mg butylated hydroxytoluene (BHT).

Signs of contact dermatitis after dermal exposure to butylated hydroxytoluene (BHT) and allergic reactions after oral intake of a mixture of butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA) were occasionally reported ³⁵. In another report (Goodman et al., 1990), two patients with chronic
idiopathic urticaria developed exacerbations when challenged with butylated hydroxytoluene (BHT)/butylated hydroxyanisole (BHA), but had less symptomsafter cons uming a butylated hydroxytoluene (BHT)/butylated hydroxyanisole (BHA)-free diet.

When patch-tested on more than 15 individuals, butylated hydroxytoluene (BHT) showed mild skin irritation; a positive skin reaction 14 days later was interpreted as sensitization ³⁶.

Recent patch test results obtained from the medical surveillance of great numbers of workers ³⁷ or patients ³⁸ were all negative.

The European Food Safety Authority (EFSA) Panel noted that these limited reports do not allow any conclusions to be drawn about sensitization to butylated hydroxytoluene (BHT) following oral intake.

Human studies: case studies

Shilian and Goldstone ³⁹ reported a case of gastritis caused by ingestion of butylated hydroxytoluene (BHT) in a 22-year-old woman who ingested 4 g of butylated hydroxytoluene (BHT) on an empty stomach two days before the onset of the gastritis. This amounts to an acute dose of about 67 mg/kg bw assuming a body weight of 60 kg. Later that evening she experienced severe epigastric cramping, generalized weakness, nausea and vomiting, followed by dizziness, confusion and a brief loss of consciousness.

A similar case study was reported by Grogan ⁴⁰. A 24-year-old woman complained of lightheadedness, unsteadiness of gait and slurred speech. On examination the following findings were noted: dysarthria, wide-based gait, a positive Romberg test, slowed mentation without thought disorder and dysmetria of the left (non-dominant arm). On the evening before admission the patient ingested 80 grams of butylated hydroxytoluene (BHT) suspended in safflower oil on an empty stomach. This dose is estimated to be equivalent to about 1.3 g/kg bw, assuming a 60 kg body weight.

Special studies on hemorrhagic effects

The EU Scientific Committee for Food (SCF) ⁴¹ concluded that a series of studies has shown that some, but not all species tested show hemorrhage and/or a reduction in blood prothrombin index after dosing with butylated hydroxytoluene (BHT). The mechanisms by which butylated hydroxytoluene (BHT) brings about these effects appear to be several but the major effect is a reduction in activity of certain clotting factors, principally those which are vitamin K-dependent. The most susceptible species for hemorrhagic effects appears to be the rat, and for this species the NOAEL for transient reduction (1 week duration) of the prothrombin index was approximately 9 mg/kg body weight/day, and for persistent reduction (4 week duration), approximately 250 mg/kg body weight/day given with the diet. Chickens may also respond with hemorrhage of the liver ⁴².

Administration to groups of five male Slc:ddY mice of 0.5%, 1.0% or 2.0% butylated hydroxytoluene (BHT) in a purified diet (equivalent to 660, 1390 or 2860 mg/kg body weight/day) for 21 days resulted in a dose-related increase in the mortality due to massive haemorrhage in the lungs ²².

Administration to groups of five male Slc:ddY mice of 0.5%, 1.0% or 2.0% butylated hydroxytoluene (BHT) in a purified diet (equivalent to 660, 1390 or 2860 mg/kg body weight/day) for 21 days resulted in a dose-related increase in the mortality due to massive hemorrhage in the lungs ²².

Special studies on effects on the thyroid

Rats were fed 0, 500 or 5000 mg butylated hydroxytoluene (BHT)/kg of feed (estimated to be equivalent to approximately 25 or 250 mg/kg bw/day) for 8, 26 or 90 days and the uptake of 125I by the thyroid was determined. The presence of butylated hydroxytoluene (BHT) in the diet resulted in a marked increase in the uptake of 125I at all time periods studied. When rats were fed butylated hydroxytoluene (BHT) in diets containing varying amounts of iodine (0.12, 0.15 or 0.3 mg iodine/kg feed) for 30 days, there was a significant increase in thyroid weight in butylated hydroxytoluene (BHT) treated animals when compared to controls. butylated hydroxytoluene (BHT) did not change levels of T3 and T4 in the blood. The biological half-life of thyroxine was increased after 13 days on a butylated hydroxytoluene (BHT) diet but returned to normal after 75 days. Electron microscopy of the thyroid glands of rats exposed to 250 mg butylated hydroxytoluene (BHT)/kg bw/day for 28 days showed an increase in the number of follicle cells ²².

Based on this observation the European Food Safety Authority (EFSA) Panel noted that the NOAEL of this study would be 25 mg/kg body weight/day.

Although rodents and humans share a common physiology in regard to the thyroid-pituitary feedback system, a number of factors contribute to the greater sensitivity of the rat to long-term perturbation of the pituitary thyroid axis which predisposes it to a higher incidence of proliferative lesions in response to chronic TSH stimulation than human thyroid.

Both humans and rodents have nonspecific low affinity protein carriers of thyroid hormone (e.g., albumin). However, in humans, other primates, and dogs there is a high affinity binding protein, thyroxine-binding globulin (TBG), which binds T4 (and T3 to a lesser degree); this protein is not present in rodents, birds, amphibians and fish, and has a 1000-fold greater binding affinity than nonspecific low affinity protein carriers.

Although qualitatively the rat is an indicator of a potential human thyroid cancer hazard, humans appear to be quantitatively less sensitive than rodents to developing cancer from perturbations in thyroid-pituitary status. Given that the rodent is a sensitive model for measuring the carcinogenic influences of TSH and that humans appear to be less responsive, effects on rodents would represent a conservative indicator of potential risk for humans. Rodent cancer studies typically include doses that lead to toxicity, including perturbation in thyroid-pituitary function over a lifetime. The relevance of the experimental conditions to anticipated human exposure scenarios (i.e., dose, frequency and time) should be considered. In addition, chemically-induced effects that are produced by short-term disruption in thyroid-pituitary function appear to be reversible, when the stimulus is removed.

Summary

Butylated hydroxytoluene (BHT) is a synthetic antioxidant authorized as a food additive in the European Union that was previously evaluated by the European Union Scientific Committee for Food (SCF) in 1987 and the Joint FAO/WHO Expert Committee on Food Additives (JECFA) several times, the latest in 1996.

The European Food Safety Authority (EFSA) Panel concluded that the present database justifies the revision of the Acceptable Daily Intake (ADI) of 0-0.05 mg/kg body weight/day set by the European Union Scientific Committee for Food (SCF).

Based on a No-observed-adverse-effect level (NOAEL) of 25 mg/kg body weight/day from two 2-generation studies in rats and an uncertainty factor of 100, the European Food Safety Authority (EFSA) Panel derived an ADI of 0.25 mg/kg body weight/day.

Since the NOAEL of 25 mg/kg body weight/day for the reproductive effects is below the BMDL10 values for hepatocellular carcinomas in long-term studies with butylated hydroxytoluene (BHT), the Panel concluded that this NOAEL also covers this effect.

The European Food Safety Authority (EFSA) Panel noted that exposure of adults to butylated hydroxytoluene (BHT) from its use as food additive is unlikely to exceed the newly derived Acceptable Daily Intake (ADI) of 0.25 mg/kg body weight/day at the mean and for the high consumers (95th percentile). Exposure of children to butylated hydroxytoluene (BHT) from its use as food additive is also unlikely to exceed this ADI at the mean, but is exceeded for some European countries (Finland, The Netherlands) at the 95th percentile. If exposure to butylated hydroxytoluene (BHT) from its use as food contact material is also taken into account the new ADI would be exceeded by children at the mean and at the 95th percentile.

Butylated hydroxytoluene MSDS

Butylated hydroxytoluene solubility:

• less than 1 mg/mL at 68° F (20 °C).
• Insoluble in water and propane- 1,2-diol;
• Freely soluble in ethanol
• Freely soluble in toluene; soluble in methanol, isopropanol, methyl ethyl ketone, acetone, cellosolve, benzene, most hydrocarbon solvents, ethanol, petroleum ether, liquid petrolatum (white oil): 0.5% wt/wt; more sol in food oils and fats than butylated hydroxyanisol; good solubility in linseed oil. Insoluble in propylene glycol ⁴³
• Soluble in ethanol, acetone, benzene, petroleum ether; Insoluble in alkali ⁴⁴
• Soluble in naphtha; insoluble in 10% sodium hydroxide ⁴⁵
• In water, 0.6 mg/L at 77° F (25 °C) ⁴⁶
• In water, 0.4 mg/L at 68° F (20 °C)

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