- Foods that boost immune system
- List of foods containing Vitamins and Minerals that Affect the Immune System
Foods that boost immune system
There are no special diets or particular foods that will directly boost your immune system 1) and there is no quick fix to boost your immune system. But there are things you can do to keep your immunity up. Eating a healthy balanced diet does promote good immune functioning and mood. A healthy balanced diet includes 5 portions (handfuls) of fruit and vegetables a day and good sources of protein, iron and calcium. Starchy carbohydrates (bread, pasta, rice, cereal), are also part of a healthy balanced diet. These are your energy foods, so if you aren’t exercising as much as you normally would, taking care of your portion sizes would be useful to maintain your weight. Making sure you drink plenty of fluid is also important, you should be aiming for 1.5-2L a day. Minding your alcohol consumption is also good for body and mind.
Although there is no diet that will directly boost your immune system, certain foods have been shown to fight inflammation and strengthen bones. Adding these foods to your balanced diet may boost your immune system and may help ease the symptoms of your arthritis. For example, certain types of fish are packed with inflammation-fighting Omega-3 fatty acids, experts recommend at least 3 to 4 ounces of fish, twice a week. Omega-3-rich fish include salmon, tuna, mackerel and herring. If you don’t like oily fish, you can try healthy soybeans (tofu or edamame). Soybeans are also low in fat, high in protein and fiber and an all-around good-for-you food. Extra virgin olive oil is loaded with heart-healthy fats, as well as oleocanthal (a phenolic compound), which has properties similar to non-steroidal, anti-inflammatory drugs 2). A substantial number of investigations examined the biological functions of olive oil, suggesting phenolic compounds as being the beneficial constituents 3). Those compounds found in extra virgin olive oil have also been shown to bear antioxidant, anti-inflammatory, and anti-thrombotic activities; nevertheless, the exact mechanism of action remains unknown 4). But olive oil not the only oil with health benefits. Avocado and safflower oils have shown cholesterol-lowering properties, while walnut oil has 10 times the omega-3s that olive oil has.
Studies have shown cherries help reduce the frequency of gout attacks. Research has shown that the anthocyanins found in cherries have an anti-inflammatory effect 5). Anthocyanins are widespread in red or blue fruits and vegetables and their content in plants varies markedly among different species, depending on cultivar or variety, growing area, climate, farming methods, harvest time, ripening, seasonal variability, processing and storage, temperature and light exposure 6). Berries such as strawberries, blueberries, blackberries, blackcurrant, redcurrant and raspberries are a rich source of anthocyanins, with levels ranging from about 100 to about 700 mg/100 g of fresh product 7), but the highest content is found in elderberries and chokeberries, which can contain up to 1,4-1,8 g of anthocyanins per 100 g of product 8). Other good sources of anthocyanins include purple corn, cherries, plums, pomegranate, eggplant, wine, grapes, and red/purple vegetables such as black carrots, red cabbage and purple cauliflower which may contain from a few milligrams up to 200–300 mg/100 g of product 9). More recently, anthocyanins have been identified in numerous berries whose production and consumption is steadily increasing, such as maqui 10), myrtle 11) and açai 12).
Low-fat dairy products, like milk, yogurt and cheese are packed with calcium and vitamin D, both found to increase bone strength. Vitamin D is essential for calcium absorption, and it has been shown to boost the immune system. If dairy doesn’t agree with you, aim for other calcium and vitamin D-rich foods like leafy green vegetables.
Rich in vitamins K and C, broccoli also contains a compound called sulforaphane, which researchers have found could help prevent or slow the progression of osteoarthritis (OA). Broccoli is also rich in calcium, which is known for its bone-building benefits.
Green tea is packed with polyphenols, antioxidants believed to reduce inflammation and slow cartilage destruction. Studies also show that another antioxidant in green tea called epigallocatechin-3-gallate (EGCG) blocks the production of molecules that cause joint damage in people with rheumatoid arthritis.
Citrus fruits – like oranges, grapefruits and limes – are rich in vitamin C. Research shows that getting the right amount of vitamin aids in preventing inflammatory arthritis and maintaining healthy joints with osteoarthritis.
Beans are packed with fiber, a nutrient that helps lower C-reactive protein (CRP). CRP is used to identify the presence of inflammation, to determine its severity, and to monitor response to treatment. Beans are also an excellent and inexpensive – source of protein, which is important for muscle health. Some beans are rich in folic acid, magnesium, iron, zinc and potassium, all known for their heart and immune system benefits. Look for red beans, kidney beans and pinto beans.
Studies have shown that people who regularly ate foods from the allium family – such as garlic, onions and leeks – showed fewer signs of early osteoarthritis. Researchers believe the compound diallyl disulphine found in garlic may limit cartilage-damaging enzymes in human cells.
Nuts are rich in protein, calcium, magnesium, zinc, vitamin E and immune-boosting alpha linolenic acid (ALA), as well as filling protein and fiber. They are heart-healthy and beneficial for weight loss. Try walnuts, pine nuts, pistachios and almonds.
Why is nutrition important?
Good nutrition means getting enough macronutrients and micronutrients.
- Macronutrients contain calories (energy): proteins, carbohydrates, and fats. They help you maintain your body weight.
- Micronutrients include vitamins and minerals. They keep your cells working properly, but will not prevent weight loss.
Nutrition is important for everyone because food gives your bodies the nutrients they need to stay healthy, grow, and work properly. Foods are made up of six classes of nutrients, each with its own special role in the body:
- Protein builds muscles and a strong immune system.
- Carbohydrates (including vegetables, fruits, grains) give you energy.
- Fat gives you extra energy.
- Vitamins regulate body processes.
- Minerals regulate body processes and also make up body tissues.
- Water gives cells shape and acts as a medium where body processes can occur.
Having good nutrition means eating the right types of foods in the right amounts so you get these important nutrients.
HIV also called the human immunodeficiency virus. People who are infected with HIV (human immunodeficiency virus) – the HIV virus attacks their immune system (specifically the CD4 cells, often called T lymphocyte cells), the body’s natural defense system 13). These special cells help the immune system fight off infections. Over time, the HIV virus can destroy so many of these cells that the body can’t fight off infections and disease. Without a strong immune system, the body has trouble fighting off disease. This puts you at risk for serious infections and certain cancers.
Untreated, HIV reduces the number of CD4 cells (T cells) in the body. This damage to the immune system makes it harder and harder for the body to fight off infections and some other diseases. Opportunistic infections or cancers take advantage of a very weak immune system and signal that the person has AIDS (acquired immunodeficiency syndrome). AIDS is the last stage of HIV infection and people with AIDS have have such badly damaged immune systems that they get an increasing number of severe illnesses, called opportunistic infections. People with AIDS get infections or cancers that rarely occur in healthy people and these can be deadly.
No effective cure currently exists, but with proper medical care, HIV can be controlled. When you are infected with HIV, your immune system has to work very hard to fight off infections–and this takes energy (measured in calories). For some people, this may mean you need to eat more food than you used to 14).
If you are underweight–or you have advanced HIV disease, high viral loads, or opportunistic infections–you should include more protein as well as extra calories (in the form of carbohydrates and fats) 15).
Weight loss can be a common problem for people with relatively advanced stages of HIV infection, and it should be taken very seriously. Losing weight can be dangerous because it makes it harder for your body to fight infections and to get well after you’re sick.
People with advanced HIV often do not eat enough because:
- HIV may reduce your appetite, make food taste bad, and prevent the body from absorbing food in the right way. Some HIV medicines may also cause these symptoms (if this is so, tell your HIV specialist–you may be able to change to medications that do not have these side effects).
- symptoms like a sore mouth, nausea, and vomiting make it difficult to eat
- fatigue from HIV or medicines may make it hard to prepare food and eat regularly
To keep your weight up, you will need to take in more protein and calories. What follows are ways to do that.
To add protein to your diet
Protein-rich foods include meats, fish, beans, dairy products, and nuts. To boost the protein in your meals:
- Spread nut butter on toast, crackers, fruit, or vegetables.
- Add cottage cheese to fruit and tomatoes.
- Add canned tuna to casseroles and salads.
- Add shredded cheese to sauces, soups, omelets, baked potatoes, and steamed vegetables.
- Eat yogurt on your cereal or fruit.
- Eat hard-boiled (hard-cooked) eggs. Use them in egg-salad sandwiches or slice and dice them for tossed salads.
- Eat beans and legumes (pinto and other beans, lentils, etc), nuts, and seeds
- Add diced or chopped meats to soups, salads, and sauces.
- Add dried milk powder or egg white powder to foods (like scrambled eggs, casseroles, and milkshakes).
To add calories to your diet
The best way to increase calories is to add extra fat and carbohydrates to your meals.
Fats are more concentrated sources of calories. Add moderate amounts of the following to your meals:
- olive oil, soybean oil, canola oil, sour cream, cream cheese, peanut butter
- gravy, sour cream, cream cheese, grated cheese
- avocados, olives, salad dressing
Carbohydrates include both starches and simple sugars.
Starches are in:
- breads, muffins, biscuits, crackers
- oatmeal and cold cereals
Simple sugars are in:
- fresh or dried fruit (raisins, dates, apricots, etc)
- jelly, honey, and maple syrup added to cereal, pancakes, and waffles
When you become ill, you often lose your appetite. This can lead to weight loss, which can make it harder for your body to fight infection.
Here are some tips for increasing your appetite:
- Try a little exercise, like walking or doing yoga. This can often stimulate your appetite and make you feel like eating more.
- Eat smaller meals more often. For instance, try to snack between meals.
- Eat whenever your appetite is good.
- Avoid drinking too much right before or during meals. This can make you feel full.
- Avoid carbonated (fizzy) drinks and foods such as cabbage, broccoli, and beans. These foods and drinks can create gas in your stomach and make you feel full and bloated.
- Eat with your family or friends.
- Choose your favorite foods, and make meals as attractive to you as possible. Try to eat in a pleasant location.
Many of us don’t drink enough water every day. You should be getting at least 8-10 glasses of water (or other fluids, such as juices or soups) a day.
Here are some tips on getting the extra fluids you need:
- Drink more water than usual. Try other fluids, too, like noncaffeinated teas, flavored waters, or fruit juice mixed with water.
- Avoid colas, coffee, tea, and cocoa. These may contain caffeine and can actually dehydrate you. Read the labels on drinks to see if they have caffeine in them.
- Avoid alcohol.
- Begin and end each day by drinking a glass of water.
- Suck on ice cubes and popsicles.
Note: If you have diarrhea or are vomiting, you will lose a lot of fluids and will need to drink more than usual.
People with HIV need extra vitamins and minerals to help repair and heal cells that have been damaged.
Even though vitamins and minerals are present in many foods, your health care provider may recommend a vitamin and mineral supplement (a pill or other form of concentrated vitamins and minerals). While vitamin and mineral supplements can be useful, they can’t replace eating a healthy diet.
Vitamins and minerals that affect the immune system
Table 1. Vitamins and minerals that affect the immune system
|Name||What It Does||Where to Get It||About Supplements|
|Vitamin A and beta-carotene||Keeps skin, lungs, and stomach healthy.||liver, whole eggs, milk, dark green, yellow, orange, and red vegetables and fruit (like spinach, pumpkin, green peppers, squash, carrots, papaya, and mangoes). Also found in orange and yellow sweet potatoes||It’s best to get vitamin A from food. Vitamin A supplements are toxic in high doses. Supplements of beta-carotene (the form of vitamin A in fruits and vegetables) have been shown to increase cancer risk in smokers.|
|Vitamin B-group (B-1, B-2, B-6, B-12, Folate)||Keeps the immune and nervous system healthy.||white beans, potatoes, meat, fish, chicken, watermelon, grains, nuts, avocados, broccoli, and green leafy vegetables|
|Vitamin C||Helps protect the body from infection and aids in recovery.||citrus fruits (like oranges, grapefruit, and lemons), tomatoes, and potatoes|
|Vitamin D||Important for developing and maintaining heathy bones and teeth.||fortified milk, fatty fish, sunlight|
|Vitamin E||Protects cells and helps fight off infection.||green leafy vegetables, vegetable oils, avocados, almonds||Limit to 400 IU per day.|
|Iron||Not having enough iron can cause anemia.||green leafy vegetables, whole grain breads and pastas, dried fruit, beans, red meat, chicken, liver, fish, and eggs||Limit to 45 mg per day unless otherwise instructed by your doctor. Iron may be a problem for people with HIV because it can increase the activity of some bacteria. Supplements that do not contain iron may be better.|
|Selenium||Important for the immune system.||whole grains, meat, fish, poultry, eggs, peanut butter, and nuts||Limit to 400 mcg per day.|
|Zinc||Important for the immune system.||meat, fish, poultry, beans, peanuts, and milk and dairy products||Limit to 40 mg per day.|
List of foods containing Vitamins and Minerals that Affect the Immune System
Vitamin A is name of a group of fat-soluble vitamin (retinoids, including retinol, retinal, and retinyl esters) 17), 18), 19), that is naturally present in many foods.
Vitamin A is important for normal vision, gene expression, the immune system, embryonic development, growth, and reproduction. Vitamin A also helps the heart, lungs, kidneys, and other organs work properly 20).
There are two different types of vitamin A 21).
- The first type, preformed vitamin A (retinol and its esterified form, retinyl ester), is found in meat (especially liver), poultry, fish, and dairy products.
- The second type, provitamin A carotenoids (beta-carotene, alpha-carotene and beta-cryptoxanthin), is found in fruits, vegetables, and other plant-based products (oily fruits and red palm oil). The most common type of provitamin A carotenoids in foods and dietary supplements is beta-carotene (β-carotene). The body converts these plant pigments into vitamin A.
You can get recommended amounts of vitamin A by eating a variety of foods, including the following:
- Beef liver and other organ meats (but these foods are also high in cholesterol, so limit the amount you eat).
- Some types of fish, such as salmon.
- Green leafy vegetables and other green, orange, and yellow vegetables, such as broccoli, carrots, and squash.
- Fruits, including cantaloupe, apricots, and mangos.
- Dairy products, which are among the major sources of vitamin A for Americans.
- Fortified breakfast cereals.
Table 2 suggests many dietary sources of vitamin A. The foods from animal sources contain primarily preformed vitamin A, the plant-based foods have provitamin A, and the foods with a mixture of ingredients from animals and plants contain both preformed vitamin A and provitamin A.
Table 2: Selected Food Sources of Vitamin A
|Food||mcg RAE per|
|Sweet potato, baked in skin, 1 whole||1,403||28,058||561|
|Beef liver, pan fried, 3 ounces||6,582||22,175||444|
|Spinach, frozen, boiled, ½ cup||573||11,458||229|
|Carrots, raw, ½ cup||459||9,189||184|
|Pumpkin pie, commercially prepared, 1 piece||488||3,743||249|
|Cantaloupe, raw, ½ cup||135||2,706||54|
|Peppers, sweet, red, raw, ½ cup||117||2,332||47|
|Mangos, raw, 1 whole||112||2,240||45|
|Black-eyed peas (cowpeas), boiled, 1 cup||66||1,305||26|
|Apricots, dried, sulfured, 10 halves||63||1,261||25|
|Broccoli, boiled, ½ cup||60||1,208||24|
|Ice cream, French vanilla, soft serve, 1 cup||278||1,014||20|
|Cheese, ricotta, part skim, 1 cup||263||945||19|
|Tomato juice, canned, ¾ cup||42||821||16|
|Herring, Atlantic, pickled, 3 ounces||219||731||15|
|Ready-to-eat cereal, fortified with 10% of the DV for vitamin A, ¾–1 cup (more heavily fortified cereals might provide more of the DV)||127–149||500||10|
|Milk, fat-free or skim, with added vitamin A and vitamin D, 1 cup||149||500||10|
|Baked beans, canned, plain or vegetarian, 1 cup||13||274||5|
|Egg, hard boiled, 1 large||75||260||5|
|Summer squash, all varieties, boiled, ½ cup||10||191||4|
|Salmon, sockeye, cooked, 3 ounces||59||176||4|
|Yogurt, plain, low fat, 1 cup||32||116||2|
|Pistachio nuts, dry roasted, 1 ounce||4||73||1|
|Tuna, light, canned in oil, drained solids, 3 ounces||20||65||1|
|Chicken, breast meat and skin, roasted, ½ breast||5||18||0|
*DV = Daily Value. DVs were developed by the FDA to help consumers compare the nutrient contents of products within the context of a total diet. The DV for vitamin A is 5,000 IU for adults and children age 4 and older. Foods providing 20% or more of the DV are considered to be high sources of a nutrient.[Source 22)]
Beta-carotene is a red-orange pigment found in plants and fruits, especially carrots and colorful vegetables. It is the yellow/orange pigment that gives vegetables and fruits their rich colors.
Carotene is an orange photosynthetic pigment important for photosynthesis. It is responsible for the orange colour of the carrot and many other fruits and vegetables. It contributes to photosynthesis by transmitting the light energy it absorbs to chlorophyll. Chemically, carotene is a terpene. It is the dimer of retinol (vitamin A) and comes in two primary forms: alpha- and beta-carotene. Gamma-, delta- and epsilon-carotene also exist. Carotene can be stored in the liver and converted to vitamin A as needed.
Beta-carotene in itself is not an essential nutrient, but vitamin A is.
Beta-carotene is a carotenoid that is a precursor of vitamin A and the human body converts beta-carotene into vitamin A (retinol). We need vitamin A for healthy skin and mucus membranes, our immune system, and good eye health and vision.
Beta-carotene, like all carotenoids, is an antioxidant. An antioxidant is a substance that inhibits the oxidation of other molecules; it protects the body from free radicals.
Free radicals damage cells through oxidation. Eventually, the damage caused by free radicals can cause several chronic illnesses.
Several studies have shown that antioxidants through diet help people’s immune systems, protect against free radicals, and lower the risk of developing cancer and heart disease.
Some studies have suggested that those who consume at least four daily servings of beta-carotene rich fruits and/or vegetables have a lower risk of developing cancer or heart disease.
Beta-carotene may also slow down cognitive decline. Men who have been taking beta-carotene supplements for 15 or more years are considerably less likely to experience cognitive decline than other males, researchers from Harvard Medical School reported in Archives of Internal Medicine.
Thiamin (Vitamin B1)
Thiamin (or thiamine) is one of the water-soluble B vitamins. It is also known as vitamin B1. Thiamin is naturally present in some foods, added to some food products, and available as a dietary supplement. This vitamin plays a critical role in energy metabolism and, therefore, in the growth, development, and function of cells 23).
Thiamin (also called vitamin B1) helps turn the food you eat into the energy you need. Thiamin is important for the growth, development, and function of the cells in your body.
Table 3: Selected Food Sources of Thiamine
|Breakfast cereals, fortified with 100% of the DV for thiamin, 1 serving||1.5||100|
|Rice, white, long grain, enriched, parboiled, ½ cup||1.4||73|
|Egg noodles, enriched, cooked, 1 cup||0.5||33|
|Pork chop, bone-in, broiled, 3 ounces||0.4||27|
|Trout, cooked, dry heat, 3 ounces||0.4||27|
|Black beans, boiled, ½ cup||0.4||27|
|English muffin, plain, enriched, 1 muffin||0.3||20|
|Mussels, blue, cooked, moist heat, 3 ounces||0.3||20|
|Tuna, Bluefin, cooked, dry heat, 3 ounces||0.2||13|
|Macaroni, whole wheat, cooked, 1 cup||0.2||13|
|Acorn squash, cubed, baked, ½ cup||0.2||13|
|Rice, brown, long grain, not enriched, cooked, ½ cup||0.1||7|
|Bread, whole wheat, 1 slice||0.1||7|
|Orange juice, prepared from concentrate, 1 cup||0.1||7|
|Sunflower seeds, toasted, 1 ounce||0.1||7|
|Beef steak, bottom round, trimmed of fat, braised, 3 ounces||0.1||7|
|Yogurt, plain, low fat, 1 cup||0.1||7|
|Oatmeal, regular and quick, unenriched, cooked with water, ½ cup||0.1||7|
|Corn, yellow, boiled, 1 medium ear||0.1||7|
|Milk, 2%, 1 cup||0.1||7|
|Barley, pearled, cooked, 1 cup||0.1||7|
|Cheddar cheese, 1½ ounces||0||0|
|Chicken, meat and skin, roasted, 3 ounces||0||0|
|Apple, sliced, 1 cup||0||0|
*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 thiamine is 1.5 mg for adults and children age 4 and older. Foods providing 20% or more of the DV are considered to be high sources of a nutrient.[Source 24)]
Vitamin B2 (Riboflavin)
Riboflavin (also called vitamin B2) is one of the B vitamins, which are all water soluble and it’s important for the growth, development, and function of the cells in your body. It also helps turn the food you eat into the energy you need.
More than 90% of dietary riboflavin is in the form of flavin adenine dinucleotide (FAD) or flavin mononucleotide (FMN); the remaining 10% is comprised of the free form and glycosides or esters 25), 26). Most riboflavin is absorbed in the proximal small intestine 27). The body absorbs little riboflavin from single doses beyond 27 mg and stores only small amounts of riboflavin in the liver, heart, and kidneys. When excess amounts are consumed, they are either not absorbed or the small amount that is absorbed is excreted in urine 28).
Bacteria in the large intestine produce free riboflavin that can be absorbed by the large intestine in amounts that depend on the diet. More riboflavin is produced after ingestion of vegetable-based than meat-based foods 29).
Riboflavin is yellow and naturally fluorescent when exposed to ultraviolet light 30). Moreover, ultraviolet and visible light can rapidly inactivate riboflavin and its derivatives. Because of this sensitivity, lengthy light therapy to treat jaundice in newborns or skin disorders can lead to riboflavin deficiency. The risk of riboflavin loss from exposure to light is the reason why milk is not typically stored in glass containers 31), 32).
Table 4: Selected Food Sources of Riboflavin
|Beef liver, pan fried, 3 ounces||2.9||171|
|Breakfast cereals, fortified with 100% of the DV for riboflavin, 1 serving||1.7||100|
|Oats, instant, fortified, cooked with water, 1 cup||1.1||65|
|Yogurt, plain, fat free, 1 cup||0.6||35|
|Milk, 2% fat, 1 cup||0.5||29|
|Beef, tenderloin steak, boneless, trimmed of fat, grilled, 3 ounces||0.4||24|
|Clams, mixed species, cooked, moist heat, 3 ounces||0.4||24|
|Mushrooms, portabella, sliced, grilled, ½ cup||0.3||18|
|Almonds, dry roasted, 1 ounce||0.3||18|
|Cheese, Swiss, 3 ounces||0.3||18|
|Rotisserie chicken, breast meat only, 3 ounces||0.2||12|
|Egg, whole, scrambled, 1 large||0.2||12|
|Quinoa, cooked, 1 cup||0.2||12|
|Bagel, plain, enriched, 1 medium (3½”–4” diameter)||0.2||12|
|Salmon, pink, canned, 3 ounces||0.2||12|
|Spinach, raw, 1 cup||0.1||6|
|Apple, with skin, 1 large||0.1||6|
|Kidney beans, canned, 1 cup||0.1||6|
|Macaroni, elbow shaped, whole wheat, cooked, 1 cup||0.1||6|
|Bread, whole wheat, 1 slice||0.1||6|
|Cod, Atlantic, cooked, dry heat, 3 ounces||0.1||6|
|Sunflower seeds, toasted, 1 ounce||0.1||6|
|Tomatoes, crushed, canned, ½ cup||0.1||6|
|Rice, white, enriched, long grain, cooked, ½ cup||0.1||6|
|Rice, brown, long grain, cooked, ½ cup||0||0|
*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 riboflavin is 1.7 mg for adults and children age 4 and older. Foods providing 20% or more of the DV are considered to be high sources of a nutrient.[Source 33)]
Vitamin B6 (Pyridoxine)
Vitamin B6 includes a group of closely related compounds: pyridoxine, pyridoxal, and pyridoxamine. Substantial proportions of the naturally occurring pyridoxine in fruits, vegetables, and grains exist in glycosylated forms that exhibit reduced bioavailability 34). The body needs vitamin B6 for more than 100 enzyme reactions involved in metabolism. They are metabolized in the body to pyridoxal phosphate, which acts as a coenzyme in many important reactions in blood, CNS, and skin metabolism. Vitamin B6 is important in heme and nucleic acid biosynthesis and in lipid, carbohydrate, and amino acid metabolism. Vitamin B6 is also involved in brain development during pregnancy and infancy as well as immune function.
Vitamin B6 in coenzyme forms performs a wide variety of functions in the body and is extremely versatile, with involvement in more than 100 enzyme reactions, mostly concerned with protein metabolism. Both pyridoxal 5’ phosphate and pyridoxamine 5’ phosphate are involved in amino acid metabolism, and pyridoxal 5’ phosphate is also involved in the metabolism of one-carbon units, carbohydrates, and lipids 35). Vitamin B6 also plays a role in cognitive development through the biosynthesis of neurotransmitters and in maintaining normal levels of homocysteine, an amino acid in the blood 36). Vitamin B6 is involved in gluconeogenesis and glycogenolysis, immune function (for example, it promotes lymphocyte and interleukin-2 production), and hemoglobin formation 37).
The human body absorbs vitamin B6 in the jejunum. Phosphorylated forms of the vitamin are dephosphorylated, and the pool of free vitamin B6 is absorbed by passive diffusion 38).
Table 5: Selected Food Sources of Vitamin B6
|Food||Milligrams (mg) per serving||Percent DV*|
|Chickpeas, canned, 1 cup||1.1||55|
|Beef liver, pan fried, 3 ounces||0.9||45|
|Tuna, yellowfin, fresh, cooked, 3 ounces||0.9||45|
|Salmon, sockeye, cooked, 3 ounces||0.6||30|
|Chicken breast, roasted, 3 ounces||0.5||25|
|Breakfast cereals, fortified with 25% of the DV for vitamin B6||0.5||25|
|Potatoes, boiled, 1 cup||0.4||20|
|Turkey, meat only, roasted, 3 ounces||0.4||20|
|Banana, 1 medium||0.4||20|
|Marinara (spaghetti) sauce, ready to serve, 1 cup||0.4||20|
|Ground beef, patty, 85% lean, broiled, 3 ounces||0.3||15|
|Waffles, plain, ready to heat, toasted, 1 waffle||0.3||15|
|Bulgur, cooked, 1 cup||0.2||10|
|Cottage cheese, 1% low-fat, 1 cup||0.2||10|
|Squash, winter, baked, ½ cup||0.2||10|
|Rice, white, long-grain, enriched, cooked, 1 cup||0.1||5|
|Nuts, mixed, dry-roasted, 1 ounce||0.1||5|
|Raisins, seedless, ½ cup||0.1||5|
|Onions, chopped, ½ cup||0.1||5|
|Spinach, frozen, chopped, boiled, ½ cup||0.1||5|
|Tofu, raw, firm, prepared with calcium sulfate, ½ cup||0.1||5|
|Watermelon, raw, 1 cup||0.1||5|
*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 vitamin B6 is 2 mg for adults and children age 4 and older. However, the FDA does not require food labels to list vitamin B6 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.[Source 39)]
Vitamin B12 (Cyanocobalamin)
Vitamin B12 is also known as Cyanocobalamin is a nutrient that helps keep the body’s nerve and blood cells healthy and helps make DNA, the genetic material in all cells. Vitamin B12 also helps prevent a type of anemia called megaloblastic anemia that makes people tired and weak.
Vitamin B12 is a water-soluble vitamin that is naturally present in some foods, added to others, and available as a dietary supplement and a prescription medication. Vitamin B12 exists in several forms and contains the mineral cobalt 40), 41), 42), 43), so compounds with vitamin B12 activity are collectively called “cobalamins”. Methylcobalamin and 5-deoxyadenosylcobalamin are the forms of vitamin B12 that are active in human metabolism 44).
Two steps are required for the body to absorb vitamin B12 from food.
- First, food-bound vitamin B12 is released in the stomach’s acid environment (hydrochloric acid and and gastric protease in the stomach separate vitamin B12 from the protein to which vitamin B12 is attached in food) and is bound to R protein (haptocorrin) 45). When synthetic vitamin B12 is added to fortified foods and dietary supplements, it is already in free form and thus, does not require this separation step.
- Second, pancreatic enzymes cleave this B12 complex (B12-R protein) in the small intestine. After cleavage, intrinsic factor (a protein made by the stomach), secreted by parietal cells in the gastric mucosa, binds with the free vitamin B12. Intrinsic factor is required for absorption of vitamin B12, which takes place in the terminal ileum 46), 47). Approximately 56% of a 1 mcg oral dose of vitamin B12 is absorbed, but absorption decreases drastically when the capacity of intrinsic factor is exceeded (at 1–2 mcg of vitamin B12) 48). Some people have pernicious anemia, a condition where they cannot make intrinsic factor. As a result, they have trouble absorbing vitamin B12 from all foods and dietary supplements.
Several food sources of vitamin B12 are listed in Table 6.
Table 6: Selected Food Sources of Vitamin B12
|Clams, cooked, 3 ounces||84.1||1,402|
|Liver, beef, cooked, 3 ounces||70.7||1,178|
|Breakfast cereals, fortified with 100% of the DV for vitamin B12, 1 serving||6.0||100|
|Trout, rainbow, wild, cooked, 3 ounces||5.4||90|
|Salmon, sockeye, cooked, 3 ounces||4.8||80|
|Trout, rainbow, farmed, cooked, 3 ounces||3.5||58|
|Tuna fish, light, canned in water, 3 ounces||2.5||42|
|Cheeseburger, double patty and bun, 1 sandwich||2.1||35|
|Haddock, cooked, 3 ounces||1.8||30|
|Breakfast cereals, fortified with 25% of the DV for vitamin B12, 1 serving||1.5||25|
|Beef, top sirloin, broiled, 3 ounces||1.4||23|
|Milk, low-fat, 1 cup||1.2||18|
|Yogurt, fruit, low-fat, 8 ounces||1.1||18|
|Cheese, Swiss, 1 ounce||0.9||15|
|Beef taco, 1 soft taco||0.9||15|
|Ham, cured, roasted, 3 ounces||0.6||10|
|Egg, whole, hard boiled, 1 large||0.6||10|
|Chicken, breast meat, roasted, 3 ounces||0.3||5|
*DV = Daily Value. DVs were developed by the U.S. Food and Drug Administration (FDA) to help consumers determine the level of various nutrients in a standard serving of food in relation to their approximate requirement for it. The DV for vitamin B12 is 6.0 mcg. However, the FDA does not require food labels to list vitamin B12 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, but foods providing lower percentages of the DV also contribute to a healthful diet.[Source 49)]
Folate (Vitamin B9)
Folate is also known vitamin B9 (Folacin, Folic Acid, Pteroylglutamic acid) that is naturally present in many foods.
Folic Acid is a form of folate that is manufactured and used in dietary supplements and fortified foods 50).
Our bodies need folate to make DNA and other genetic material. Folate is also needed for the body’s cells to divide.
Folic acid and folate also help your body make healthy new red blood cells. Red blood cells carry oxygen to all the parts of your body. If your body does not make enough red blood cells, you can develop anemia. Anemia happens when your blood cannot carry enough oxygen to your body, which makes you pale, tired, or weak. Also, if you do not get enough folic acid, you could develop a type of anemia called folate-deficiency anemia. (source 51)).
Folate-deficiency anemia is most common during pregnancy. Other causes of folate-deficiency anemia include alcoholism and certain medicines to treat seizures, anxiety, or arthritis.
Everyone needs folic acid. Our bodies use it to make new cells.
In women and pregnant mothers, folic acid is very important because it can help prevent some major birth defects of the baby’s brain and spine (anencephaly and spina bifida). (Source 52)).
Every woman needs folic acid every day, whether she’s planning to get pregnant or not, for the healthy new cells the body makes daily. Think about the skin, hair, and nails. These – and other parts of the body – make new cells each day.
Centers for Disease Control and Prevention urges women to take 400 mcg of folic acid every day, starting at least one month before getting pregnant and while she is pregnant, to help prevent major birth defects of the baby’s brain and spine.
Folate is naturally present in many foods and food companies add folic acid to other foods, including bread, cereal, and pasta. You can get recommended amounts by eating a variety of foods, including the following:
- Leafy Green Vegetables (especially asparagus, Brussels sprouts, and dark green leafy vegetables such as spinach and mustard greens).
- Fruits and fruit juices (especially oranges and orange juice).
- Nuts, beans, and peas (such as peanuts, black-eyed peas, and kidney beans).
- Grains (including whole grains; fortified cold cereals; enriched flour products such as bread, bagels, cornmeal, and pasta; and rice).
- Folic acid is added to many grain-based products, enriched breads, cereals and corn masa flour (used to make corn tortillas and tamales, for example). To find out whether folic acid has been added to a food, check the product label.
Beef liver is high in folate but is also high in cholesterol, so limit the amount you eat. Only small amounts of folate are found in other animal foods like meats, poultry, seafood, eggs, and dairy products.
Table 7. Selected Food Sources of Folate and Folic Acid
|Beef liver, braised, 3 ounces||215||54|
|Spinach, boiled, ½ cup||131||33|
|Black-eyed peas (cowpeas), boiled, ½ cup||105||26|
|Breakfast cereals, fortified with 25% of the DV†||100||25|
|Rice, white, medium-grain, cooked, ½ cup†||90||23|
|Asparagus, boiled, 4 spears||89||22|
|Spaghetti, cooked, enriched, ½ cup†||83||21|
|Brussels sprouts, frozen, boiled, ½ cup||78||20|
|Lettuce, romaine, shredded, 1 cup||64||16|
|Avocado, raw, sliced, ½ cup||59||15|
|Spinach, raw, 1 cup||58||15|
|Broccoli, chopped, frozen, cooked, ½ cup||52||13|
|Mustard greens, chopped, frozen, boiled, ½ cup||52||13|
|Green peas, frozen, boiled, ½ cup||47||12|
|Kidney beans, canned, ½ cup||46||12|
|Bread, white, 1 slice†||43||11|
|Peanuts, dry roasted, 1 ounce||41||10|
|Wheat germ, 2 tablespoons||40||10|
|Tomato juice, canned, ¾ cup||36||9|
|Crab, Dungeness, 3 ounces||36||9|
|Orange juice, ¾ cup||35||9|
|Turnip greens, frozen, boiled, ½ cup||32||8|
|Orange, fresh, 1 small||29||7|
|Papaya, raw, cubed, ½ cup||27||7|
|Banana, 1 medium||24||6|
|Yeast, baker’s, ¼ teaspoon||23||6|
|Egg, whole, hard-boiled, 1 large||22||6|
|Vegetarian baked beans, canned, ½ cup||15||4|
|Cantaloupe, raw, 1 wedge||14||4|
|Fish, halibut, cooked, 3 ounces||12||3|
|Milk, 1% fat, 1 cup||12||3|
|Ground beef, 85% lean, cooked, 3 ounces||7||2|
|Chicken breast, roasted, ½ breast||3||1|
* DV = Daily Value. The FDA developed DVs to help consumers compare the nutrient contents of products within the context of a total diet. The DV for folate is 400 mcg for adults and children aged 4 and older. However, the FDA does not require food labels to list folate 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.
† Fortified with folic acid as part of the folate fortification program.[Source 53)]
Vitamin C, also known as L-ascorbic acid or ascorbate, is a water-soluble vitamin that is naturally present in some foods, added to others, and available as a dietary supplement. Vitamin C is synthesized from D-glucose or D-galactose by many plants and animals. However, humans lack the enzyme L-gulonolactone oxidase required for ascorbic acid synthesis and must obtain vitamin C through food or supplements 54), 55). In the body, it acts as an antioxidant, helping to protect cells from the damage caused by free radicals. Free radicals are compounds formed when our bodies convert the food we eat into energy. People are also exposed to free radicals in the environment from cigarette smoke, air pollution, and ultraviolet light from the sun.
The intestinal absorption of vitamin C is regulated by at least one specific dose-dependent, active transporter 56). Cells accumulate vitamin C via a second specific transport protein. In vitro studies have found that oxidized vitamin C, or dehydroascorbic acid, enters cells via some facilitated glucose transporters and is then reduced internally to ascorbic acid. The physiologic importance of dehydroascorbic acid uptake and its contribution to overall vitamin C economy is unknown.
Vitamin C plays a role in collagen, carnitine, hormone, and amino acid formation. It is essential for wound healing and facilitates recovery from burns. Vitamin C is also an antioxidant, supports immune function, and facilitates the absorption of iron 57). High-Dose vitamin C, when taken by intravenous (IV) infusion, vitamin C can reach much higher levels in the blood than when it is taken by mouth. Studies suggest that these higher levels of vitamin C may cause the death of cancer cells in the laboratory. Surveys of healthcare practitioners at United States complementary and alternative medicine conferences in recent years have shown that high-dose IV vitamin C is frequently given to patients as a treatment for infections, fatigue, and cancers, including breast cancer 58).
Vitamin C is required for the biosynthesis of collagen, L-carnitine, and certain neurotransmitters; vitamin C is also involved in protein metabolism 59), 60). Collagen is an essential component of connective tissue, which plays a vital role in wound healing. Vitamin C is also an important physiological antioxidant 61) and has been shown to regenerate other antioxidants within the body, including alpha-tocopherol (vitamin E) 62). Ongoing research is examining whether vitamin C, by limiting the damaging effects of free radicals through its antioxidant activity, might help prevent or delay the development of certain cancers, cardiovascular disease, and other diseases in which oxidative stress plays a causal role. In addition to its biosynthetic and antioxidant functions, vitamin C plays an important role in immune function 63) and improves the absorption of nonheme iron 64), the form of iron present in plant-based foods. Insufficient vitamin C intake causes scurvy, which is characterized by fatigue or lassitude, widespread connective tissue weakness, and capillary fragility 65), 66), 67), 68), 69), 70), 71).
Table 8: Selected Food Sources of Vitamin C
|Food||Milligrams (mg) per serving||Percent (%) DV*|
|Red pepper, sweet, raw, ½ cup||95||158|
|Orange juice, ¾ cup||93||155|
|Orange, 1 medium||70||117|
|Grapefruit juice, ¾ cup||70||117|
|Kiwifruit, 1 medium||64||107|
|Green pepper, sweet, raw, ½ cup||60||100|
|Broccoli, cooked, ½ cup||51||85|
|Strawberries, fresh, sliced, ½ cup||49||82|
|Brussels sprouts, cooked, ½ cup||48||80|
|Grapefruit, ½ medium||39||65|
|Broccoli, raw, ½ cup||39||65|
|Tomato juice, ¾ cup||33||55|
|Cantaloupe, ½ cup||29||48|
|Cabbage, cooked, ½ cup||28||47|
|Cauliflower, raw, ½ cup||26||43|
|Potato, baked, 1 medium||17||28|
|Tomato, raw, 1 medium||17||28|
|Spinach, cooked, ½ cup||9||15|
|Green peas, frozen, cooked, ½ cup||8||13|
*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 vitamin C is 60 mg for adults and children aged 4 and older. The FDA requires all food labels to list the percent DV for vitamin C. Foods providing 20% or more of the DV are considered to be high sources of a nutrient.[Source 72)]
Vitamin D is a fat-soluble vitamin that is naturally present in very few foods, added to others, and available as a dietary supplement. It is also produced endogenously when ultraviolet rays from sunlight strike the skin and trigger vitamin D synthesis. Vitamin D obtained from sun exposure, food, and supplements is biologically inert and must undergo two hydroxylations in the body for activation 73). The first occurs in the liver and converts vitamin D to 25-hydroxyvitamin D [25(OH)D], also known as calcidiol. The second occurs primarily in the kidney and forms the physiologically active 1,25-dihydroxyvitamin D [1,25(OH)2D], also known as calcitriol 74).
Vitamin D is a nutrient found in some foods that is needed for health and to maintain strong bones. It does so by helping the body absorb calcium (one of bone’s main building blocks) from food and supplements. People who get too little vitamin D may develop soft, thin, and brittle bones, a condition known as rickets in children and osteomalacia in adults.
Vitamin D is important to the body in many other ways as well. Muscles need it to move, for example, nerves need it to carry messages between the brain and every body part, and the immune system needs vitamin D to fight off invading bacteria and viruses. Together with calcium, vitamin D also helps protect older adults from osteoporosis. Vitamin D is found in cells throughout the body.
Vitamin D promotes calcium absorption in the gut and maintains adequate serum calcium and phosphate concentrations to enable normal mineralization of bone and to prevent hypocalcemic tetany. It is also needed for bone growth and bone remodeling by osteoblasts and osteoclasts 75), 76). Without sufficient vitamin D, bones can become thin, brittle, or misshapen. Vitamin D sufficiency prevents rickets in children and osteomalacia in adults 77). Together with calcium, vitamin D also helps protect older adults from osteoporosis.
Vitamin D has other roles in the body, including modulation of cell growth, neuromuscular and immune function, and reduction of inflammation 78), 79), 80). Many genes encoding proteins that regulate cell proliferation, differentiation, and apoptosis are modulated in part by vitamin D 81). Many cells have vitamin D receptors, and some convert 25(OH)D to 1,25(OH)2D.
Table 9: Selected Food Sources of Vitamin D
|Food||IUs per serving*||Percent DV**|
|Cod liver oil, 1 tablespoon||1,360||340|
|Swordfish, cooked, 3 ounces||566||142|
|Salmon (sockeye), cooked, 3 ounces||447||112|
|Tuna fish, canned in water, drained, 3 ounces||154||39|
|Orange juice fortified with vitamin D, 1 cup (check product labels, as amount of added vitamin D varies)||137||34|
|Milk, nonfat, reduced fat, and whole, vitamin D-fortified, 1 cup||115-124||29-31|
|Yogurt, fortified with 20% of the DV for vitamin D, 6 ounces (more heavily fortified yogurts provide more of the DV)||80||20|
|Margarine, fortified, 1 tablespoon||60||15|
|Sardines, canned in oil, drained, 2 sardines||46||12|
|Liver, beef, cooked, 3 ounces||42||11|
|Egg, 1 large (vitamin D is found in yolk)||41||10|
|Ready-to-eat cereal, fortified with 10% of the DV for vitamin D, 0.75-1 cup (more heavily fortified cereals might provide more of the DV)||40||10|
|Cheese, Swiss, 1 ounce||6||2|
* IUs = International Units.
** DV = Daily Value. DVs were developed by the U.S. Food and Drug Administration to help consumers compare the nutrient contents among products within the context of a total daily diet. The DV for vitamin D is currently set at 400 IU for adults and children age 4 and older. Food labels, however, are not required to list vitamin D 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, but foods providing lower percentages of the DV also contribute to a healthful diet.
Naturally occurring vitamin E exists in eight chemical forms (alpha-, beta-, gamma-, and delta-tocopherol and alpha-, beta-, gamma-, and delta-tocotrienol) that have varying levels of biological activity 83). Alpha- (or α-) tocopherol is the only form that is recognized to meet human requirements, but beta-, gamma-, and delta-tocopherols, 4 tocotrienols, and several stereoisomers may also have important biologic activity. These compounds act as antioxidants, which prevent lipid peroxidation of polyunsaturated fatty acids in cellular membranes 84).
Serum concentrations of vitamin E (alpha-tocopherol) depend on the liver, which takes up the nutrient after the various forms are absorbed from the small intestine.
Vitamin E is a fat-soluble antioxidant that stops the production of reactive oxygen species formed when fat undergoes oxidation. Scientists are investigating whether, by limiting free-radical production and possibly through other mechanisms, vitamin E might help prevent or delay the chronic diseases associated with free radicals.
Antioxidants protect cells from the damaging effects of free radicals, which are molecules that contain an unshared electron. Free radicals damage cells and might contribute to the development of cardiovascular disease and cancer 85). Unshared electrons are highly energetic and react rapidly with oxygen to form reactive oxygen species. The body forms reactive oxygen species endogenously when it converts food to energy, and antioxidants might protect cells from the damaging effects of reactive oxygen species. The body is also exposed to free radicals from environmental exposures, such as cigarette smoke, air pollution, and ultraviolet radiation from the sun. Reactive oxygen species are part of signaling mechanisms among cells.
The body also needs vitamin E to boost its immune system so that it can fight off invading bacteria and viruses. It helps to widen blood vessels and keep blood from clotting within them.
In addition to its activities as an antioxidant, vitamin E is involved in immune function and, as shown primarily by in vitro studies of cells, cell signaling, regulation of gene expression, and other metabolic processes 86). Alpha-tocopherol inhibits the activity of protein kinase C, an enzyme involved in cell proliferation and differentiation in smooth muscle cells, platelets, and monocytes 87). Vitamin-E–replete endothelial cells lining the interior surface of blood vessels are better able to resist blood-cell components adhering to this surface. Vitamin E also increases the expression of two enzymes that suppress arachidonic acid metabolism, thereby increasing the release of prostacyclin from the endothelium, which, in turn, dilates blood vessels and inhibits platelet aggregation 88).
Table 10: Selected Food Sources of Vitamin E (Alpha-Tocopherol)
|Wheat germ oil, 1 tablespoon||20.3||100|
|Sunflower seeds, dry roasted, 1 ounce||7.4||37|
|Almonds, dry roasted, 1 ounce||6.8||34|
|Sunflower oil, 1 tablespoon||5.6||28|
|Safflower oil, 1 tablespoon||4.6||25|
|Hazelnuts, dry roasted, 1 ounce||4.3||22|
|Peanut butter, 2 tablespoons||2.9||15|
|Peanuts, dry roasted, 1 ounce||2.2||11|
|Corn oil, 1 tablespoon||1.9||10|
|Spinach, boiled, ½ cup||1.9||10|
|Broccoli, chopped, boiled, ½ cup||1.2||6|
|Soybean oil, 1 tablespoon||1.1||6|
|Kiwifruit, 1 medium||1.1||6|
|Mango, sliced, ½ cup||0.7||4|
|Tomato, raw, 1 medium||0.7||4|
|Spinach, raw, 1 cup||0.6||3|
*DV = Daily Value. DVs were developed by the FDA to help consumers compare the nutrient content of different foods within the context of a total diet. The DV for vitamin E is 30 IU (approximately 20 mg of natural alpha-tocopherol) for adults and children age 4 and older. However, the FDA does not require food labels to list vitamin E 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, but foods providing lower percentages of the DV also contribute to a healthful diet.[Source 89)]
Iron is a mineral that our bodies need for many functions. In the human body, iron is present in all cells and has several vital functions — as a carrier of oxygen to the tissues from the lungs in the form of hemoglobin (Hb), as a facilitator of oxygen use and storage in the muscles as myoglobin, as a transport medium for electrons within the cells in the form of cytochromes, and as an integral part of enzyme reactions in various tissues. Too little iron can interfere with these vital functions and lead to morbidity and mortality 90), 91).
In adults, the recommended dietary allowance of iron is 8 to 11 mg per day for men and 8 to 18 mg for women in whom higher levels are recommended during pregnancy (27 mg per day) 92). Iron is poorly absorbed and body and tissue iron stores are controlled largely by modifying rates of absorption. Adequate amounts of iron are found in most Western diets, with highest levels found in red meats and moderate levels in fish, poultry, green vegetables, cereals and grains (some of which are fortified with iron).
Your body needs the right amount of iron. If you have too little iron, you may develop iron deficiency anemia. Iron deficiency is usually due to loss of iron, predominantly as a result of blood loss in the gastrointestinal tract or from menstruation and is rarely due to deficiency in intake or an inability to absorb enough iron from foods. People at higher risk of having too little iron are young children and women who are pregnant or have periods.
What foods provide iron ?
Iron is found naturally in many foods and is added to some fortified food products. You can get recommended amounts of iron by eating a variety of foods, including the following:
- Lean meat, seafood, and poultry.
- Iron-fortified breakfast cereals and breads.
- White beans, lentils, spinach, kidney beans, and peas.
- Nuts and some dried fruits, such as raisins.
Iron in food comes in two forms: heme iron and nonheme iron. Nonheme iron is found in plant foods and iron-fortified food products. Meat, seafood, and poultry have both heme and nonheme iron.
Heme iron has higher bioavailability than nonheme iron, and other dietary components have less effect on the bioavailability of heme than nonheme iron 93). The bioavailability of iron is approximately 14% to 18% from mixed diets that include substantial amounts of meat, seafood, and vitamin C (ascorbic acid, which enhances the bioavailability of nonheme iron) and 5% to 12% from vegetarian diets 94). In addition to ascorbic acid, meat, poultry, and seafood can enhance nonheme iron absorption, whereas phytate (present in grains and beans) and certain polyphenols in some non-animal foods (such as cereals and legumes) have the opposite effect 95). Unlike other inhibitors of iron absorption, calcium might reduce the bioavailability of both nonheme and heme iron. However, the effects of enhancers and inhibitors of iron absorption are attenuated by a typical mixed western diet, so they have little effect on most people’s iron status.
Several food sources of iron are listed in Table 11. Some plant-based foods that are good sources of iron, such as spinach, have low iron bioavailability because they contain iron-absorption inhibitors, such as polyphenols 96).
Your body absorbs iron from plant sources better when you eat it with meat, poultry, seafood, and foods that contain vitamin C, like citrus fruits, strawberries, sweet peppers, tomatoes, and broccoli.
Table 11: Selected Food Sources of Iron
|Breakfast cereals, fortified with 100% of the DV for iron, 1 serving||18||100|
|Oysters, eastern, cooked with moist heat, 3 ounces||8||44|
|White beans, canned, 1 cup||8||44|
|Chocolate, dark, 45%–69% cacao solids, 3 ounces||7||39|
|Beef liver, pan fried, 3 ounces||5||28|
|Lentils, boiled and drained, ½ cup||3||17|
|Spinach, boiled and drained, ½ cup||3||17|
|Tofu, firm, ½ cup||3||17|
|Kidney beans, canned, ½ cup||2||11|
|Sardines, Atlantic, canned in oil, drained solids with bone, 3 ounces||2||11|
|Chickpeas, boiled and drained, ½ cup||2||11|
|Tomatoes, canned, stewed, ½ cup||2||11|
|Beef, braised bottom round, trimmed to 1/8” fat, 3 ounces||2||11|
|Potato, baked, flesh and skin, 1 medium potato||2||11|
|Cashew nuts, oil roasted, 1 ounce (18 nuts)||2||11|
|Green peas, boiled, ½ cup||1||6|
|Chicken, roasted, meat and skin, 3 ounces||1||6|
|Rice, white, long grain, enriched, parboiled, drained, ½ cup||1||6|
|Bread, whole wheat, 1 slice||1||6|
|Bread, white, 1 slice||1||6|
|Raisins, seedless, ¼ cup||1||6|
|Spaghetti, whole wheat, cooked, 1 cup||1||6|
|Tuna, light, canned in water, 3 ounces||1||6|
|Turkey, roasted, breast meat and skin, 3 ounces||1||6|
|Nuts, pistachio, dry roasted, 1 ounce (49 nuts)||1||6|
|Broccoli, boiled and drained, ½ cup||1||6|
|Egg, hard boiled, 1 large||1||6|
|Rice, brown, long or medium grain, cooked, 1 cup||1||6|
|Cheese, cheddar, 1.5 ounces||0||0|
|Cantaloupe, diced, ½ cup||0||0|
|Mushrooms, white, sliced and stir-fried, ½ cup||0||0|
|Cheese, cottage, 2% milk fat, ½ cup||0||0|
|Milk, 1 cup||0||0|
* 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 iron is 18 mg for adults and children age 4 and older. Foods providing 20% or more of the DV are considered to be high sources of a nutrient.[Source 97)]
Selenium is a trace element that is naturally present in many foods, added to others, and available as a dietary supplement. Selenium, which is nutritionally essential for humans, is a constituent of more than two dozen selenoproteins that play critical roles in reproduction, thyroid hormone metabolism, DNA synthesis, and protection from oxidative damage and infection 98).
Selenium exists in two forms:
- inorganic (selenate and selenite) and
- organic (selenomethionine and selenocysteine) 99).
Both forms can be good dietary sources of selenium 100). Soils contain inorganic selenites and selenates that plants accumulate and convert to organic forms, mostly selenocysteine and selenomethionine and their methylated derivatives.
Selenium is important for reproduction, thyroid gland function, DNA production, and protecting the body from damage caused by free radicals and from infection 101), 102). Selenium is incorporated into selenoproteins that have a wide range of pleiotropic effects, ranging from antioxidant and anti-inflammatory effects to the production of active thyroid hormone 103). In the past 10 years, the discovery of disease-associated polymorphisms in selenoprotein genes has drawn attention to the relevance of selenoproteins to health. Low selenium status has been associated with increased risk of mortality, poor immune function, and cognitive decline. Higher selenium status or selenium supplementation has antiviral effects, is essential for successful male and female reproduction, and reduces the risk of autoimmune thyroid disease. Prospective studies have generally shown some benefit of higher selenium status on the risk of prostate, lung, colorectal, and bladder cancers, but findings from trials have been mixed, which probably emphasises the fact that supplementation will confer benefit only if intake of a nutrient is inadequate. Supplementation of people who already have adequate intake with additional selenium might increase their risk of type-2 diabetes. The crucial factor that needs to be emphasised with regard to the health effects of selenium is the inextricable U-shaped link with status; whereas additional selenium intake may benefit people with low status, those with adequate-to-high status might be affected adversely and should not take selenium supplements.
Table 12: Selected Food Sources of Selenium
|Brazil nuts, 1 ounce (6–8 nuts)||544||777|
|Tuna, yellowfin, cooked, dry heat, 3 ounces||92||131|
|Halibut, cooked, dry heat, 3 ounces||47||67|
|Sardines, canned in oil, drained solids with bone, 3 ounces||45||64|
|Ham, roasted, 3 ounces||42||60|
|Shrimp, canned, 3 ounces||40||57|
|Macaroni, enriched, cooked, 1 cup||37||53|
|Beef steak, bottom round, roasted, 3 ounces||33||47|
|Turkey, boneless, roasted, 3 ounces||31||44|
|Beef liver, pan fried, 3 ounces||28||40|
|Chicken, light meat, roasted, 3 ounces||22||31|
|Cottage cheese, 1% milkfat, 1 cup||20||29|
|Rice, brown, long-grain, cooked, 1 cup||19||27|
|Beef, ground, 25% fat, broiled, 3 ounces||18||26|
|Egg, hard-boiled, 1 large||15||21|
|Puffed wheat ready-to-eat cereal, fortified, 1 cup||15||21|
|Bread, whole-wheat, 1 slice||13||19|
|Baked beans, canned, plain or vegetarian, 1 cup||13||19|
|Oatmeal, regular and quick, unenriched, cooked with water, 1 cup||13||19|
|Spinach, frozen, boiled, 1 cup||11||16|
|Milk, 1% fat, 1 cup||8||11|
|Yogurt, plain, low fat, 1 cup||8||11|
|Lentils, boiled, 1 cup||6||9|
|Bread, white, 1 slice||6||9|
|Spaghetti sauce, marinara, 1 cup||4||6|
|Cashew nuts, dry roasted, 1 ounce||3||4|
|Corn flakes, 1 cup||2||3|
|Green peas, frozen, boiled, 1 cup||2||3|
|Bananas, sliced, 1 cup||2||3|
|Potato, baked, flesh and skin, 1 potato||1||1|
|Peaches, canned in water, solids and liquids, 1 cup||1||1|
|Carrots, raw, 1 cup||0||0|
|Lettuce, iceberg, raw, 1 cup||0||0|
*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 selenium is 70 mcg for adults and children aged 4 and older. 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) Nutrient Database Web site 104) lists the nutrient content of many foods and provides a comprehensive list of foods containing selenium arranged by nutrient content and by food name.[Source 105)]
Selenium is found naturally in many foods. The amount of selenium in plant foods depends on the amount of selenium in the soil where they were grown. The amount of selenium in animal products depends on the selenium content of the foods that the animals ate. You can get recommended amounts of selenium by eating a variety of foods, including the following:
- Meat, poultry, eggs, and dairy products
- Breads, cereals, and other grain products.
Zinc is involved in numerous aspects of cellular metabolism. It is required for the catalytic activity of approximately 100 enzymes, including many nicotinamide adenine dinucleotide (NADH) dehydrogenases, RNA and DNA polymerases, and DNA transcription factors as well as alkaline phosphatase, superoxide dismutase, and carbonic anhydrase 106), 107) and it plays a role in immune function 108), 109), protein synthesis 110), wound healing 111), DNA synthesis 112), 113) and cell division 114). Zinc also supports normal growth and development during pregnancy, childhood, and adolescence 115), 116), 117) and is required for proper sense of taste and smell 118). A daily intake of zinc is required to maintain a steady state because the body has no specialized zinc storage system 119).
Most Americans get enough zinc from the foods they eat.
Table 13: Selected Food Sources of Zinc
|Oysters, cooked, breaded and fried, 3 ounces||74.0||493|
|Beef chuck roast, braised, 3 ounces||7.0||47|
|Crab, Alaska king, cooked, 3 ounces||6.5||43|
|Beef patty, broiled, 3 ounces||5.3||35|
|Breakfast cereal, fortified with 25% of the DV for zinc, ¾ cup serving||3.8||25|
|Lobster, cooked, 3 ounces||3.4||23|
|Pork chop, loin, cooked, 3 ounces||2.9||19|
|Baked beans, canned, plain or vegetarian, ½ cup||2.9||19|
|Chicken, dark meat, cooked, 3 ounces||2.4||16|
|Yogurt, fruit, low fat, 8 ounces||1.7||11|
|Cashews, dry roasted, 1 ounce||1.6||11|
|Chickpeas, cooked, ½ cup||1.3||9|
|Cheese, Swiss, 1 ounce||1.2||8|
|Oatmeal, instant, plain, prepared with water, 1 packet||1.1||7|
|Milk, low-fat or non fat, 1 cup||1.0||7|
|Almonds, dry roasted, 1 ounce||0.9||6|
|Kidney beans, cooked, ½ cup||0.9||6|
|Chicken breast, roasted, skin removed, ½ breast||0.9||6|
|Cheese, cheddar or mozzarella, 1 ounce||0.9||6|
|Peas, green, frozen, cooked, ½ cup||0.5||3|
|Flounder or sole, cooked, 3 ounces||0.3||2|
* DV = Daily Value. DVs were developed by the U.S. Food and Drug Administration to help consumers compare the nutrient contents of products within the context of a total diet. The DV for zinc is 15 mg for adults and children age 4 and older. Food labels, however, are not required to list zinc 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.[Source 120)]
References [ + ]
|1.||↵||Why is nutrition important ? U.S. Department of Veterans Affairs. https://www.hiv.va.gov/patient/daily/diet/overview.asp|
|2.||↵||Segura-Carretero, A., & Curiel, J. A. (2018). Current Disease-Targets for Oleocanthal as Promising Natural Therapeutic Agent. International journal of molecular sciences, 19(10), 2899. https://doi.org/10.3390/ijms19102899|
|3.||↵||Peyrot des Gachons C, Uchida K, Bryant B, Shima A, Sperry JB, Dankulich-Nagrudny L, Tominaga M, Smith AB 3rd, Beauchamp GK, Breslin PA. Unusual pungency from extra-virgin olive oil is attributable to restricted spatial expression of the receptor of oleocanthal. J Neurosci. 2011 Jan 19;31(3):999-1009. doi: 10.1523/JNEUROSCI.1374-10.2011|
|4.||↵||Li W., Sperry J.N., Crowe A., Trojanoswki J.Q., Smith III A.B., Lee V.M.Y. Inhibition of tau fibrillization by oleocanthal via reaction with the amino groups of tau. J. Neurochem. 2009;110:1339–1351. doi: 10.1111/j.1471-4159.2009.06224.x|
|5.||↵||Tena, N., Martín, J., & Asuero, A. G. (2020). State of the Art of Anthocyanins: Antioxidant Activity, Sources, Bioavailability, and Therapeutic Effect in Human Health. Antioxidants (Basel, Switzerland), 9(5), 451. https://doi.org/10.3390/antiox9050451|
|6.||↵||Mattioli, R., Francioso, A., Mosca, L., & Silva, P. (2020). Anthocyanins: A Comprehensive Review of Their Chemical Properties and Health Effects on Cardiovascular and Neurodegenerative Diseases. Molecules (Basel, Switzerland), 25(17), 3809. https://doi.org/10.3390/molecules25173809|
|7, 9.||↵||Neveu V., Perez-Jimenez J., Vos F., Crespy V., du Chaffaut L., Mennen L., Knox C., Eisner R., Cruz J., Wishart D., et al. Phenol-Explorer: An online comprehensive database on polyphenol contents in foods. Database. 2010;2010:bap024. doi: 10.1093/database/bap024|
|8.||↵||Wu X., Beecher G.R., Holden J.M., Haytowitz D.B., Gebhardt S.E., Prior R.L. Concentrations of anthocyanins in common foods in the United States and estimation of normal consumption. J. Agric. Food Chem. 2006;54:4069–4075. doi: 10.1021/jf060300l|
|10.||↵||Vázquez-Espinosa M., González de Peredo A.V., Ferreiro-González M., Carrera C., Palma M., Barbero G.F., Espada-Bellido E. Assessment of ultrasound assisted extraction as an alternative method for the extraction of anthocyanins and total phenolic compounds from maqui berries (Aristotelia chilensis (Mol.) Stuntz) Agronomy. 2019;9:148. doi: 10.3390/agronomy9030148|
|11.||↵||González de Peredo A.V., Vázquez-Espinosa M., Espada-Bellido E., Ferreiro-González M., Amores-Arrocha A., Palma M., Barbero G.F., Jiménez-Cantizano A. Alternative ultrasound-assisted method for the extraction of the bioactive compounds present in Myrtle (Myrtus communis L.) Molecules. 2019;24:882.|
|12.||↵||Aliaño-González M.J., Ferreiro-González M., Espada-Bellido E., Carrera C., Palma M., Ayuso J., Barbero G.F., Álvarez J.Á. Extraction of anthocyanins and total phenolic compounds from Açai (Euterpe oleracea Mart.) using an experimental design methodology. Part 3: Microwave-assisted extraction. Agronomy. 2020;10:179. doi: 10.3390/agronomy10020179|
|13.||↵||What Are HIV and AIDS ? https://www.hiv.gov/hiv-basics/overview/about-hiv-and-aids/what-are-hiv-and-aids|
|14, 15.||↵||Why is nutrition important? https://www.hiv.va.gov/patient/daily/diet/overview.asp|
|16.||↵||Vitamins and minerals that affect the immune system. https://www.hiv.va.gov/patient/daily/diet/vitamin-mineral-chart.asp|
|17.||↵||Johnson EJ, Russell RM. Beta-Carotene. In: Coates PM, Betz JM, Blackman MR, et al., eds. Encyclopedia of Dietary Supplements. 2nd ed. London and New York: Informa Healthcare; 2010:115-20.|
|18.||↵||Ross CA. Vitamin A. In: Coates PM, Betz JM, Blackman MR, et al., eds. Encyclopedia of Dietary Supplements. 2nd ed. London and New York: Informa Healthcare; 2010:778-91.|
|19.||↵||Ross A. Vitamin A and Carotenoids. In: Shils M, Shike M, Ross A, Caballero B, Cousins R, eds. Modern Nutrition in Health and Disease. 10th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2006:351-75.|
|20.||↵||Institute of Medicine, US Panel on Micronutrients. Dietary reference intakes for vitamin A, boron, chromium, copper, iodine, iron, manganese, molybdenum, nickel, silicon, vanadium, and zinc. National Academies Press. Washington, DC, 2001. PMID: 25057538 www.ncbi.nlm.nih.gov/pubmed/25057538.|
|21.||↵||National Institute of Health. Vitamin A. https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional|
|22.||↵||U.S. Department of Agriculture, Agricultural Research Service. USDA National Nutrient Database for Standard Reference, Release 24. Nutrient Data Laboratory Home Page, 2011. https://www.ars.usda.gov/northeast-area/beltsville-md/beltsville-human-nutrition-research-center/nutrient-data-laboratory/|
|23.||↵||Said HM. Thiamin. In: Coates PM, Betz JM, Blackman MR, et al., eds. Encyclopedia of Dietary Supplements. 2nd ed. London and New York: Informa Healthcare; 2010:748-53.|
|24, 33, 39, 49, 53, 72, 82, 89, 97, 105, 120.||↵||U.S. Department of Agriculture, Agricultural Research Service. USDA National Nutrient Database for Standard Reference, Release 27. Nutrient Data Laboratory home page, 2014. https://ndb.nal.usda.gov/ndb/|
|25, 29.||↵||Said HM, Ross AC. Riboflavin. In: Ross AC, Caballero B, Cousins RJ, Tucker KL, Ziegler TR, eds. Modern Nutrition in Health and Disease. 11th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2014:325-30.|
|26, 28, 31.||↵||Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline 1998. https://www.nap.edu/catalog/6015/dietary-reference-intakes-for-thiamin-riboflavin-niacin-vitamin-b6-folate-vitamin-b12-pantothenic-acid-biotin-and-choline|
|27.||↵||McCormick DB. Riboflavin. In: Erdman JW, Macdonald IA, Zeisel SH, eds. Present Knowledge in Nutrition. 10th ed. Washington, DC: Wiley-Blackwell; 2012:280-92.|
|30.||↵||Rivlin RS. Riboflavin. In: Coates PM, Betz JM, Blackman MR, et al., eds. Encyclopedia of Dietary Supplements. 2nd ed. London and New York: Informa Healthcare; 2010:691-9.|
|32.||↵||Gaylord AM, Warthesen JJ, Smith DE. Influence of milk fat, milk solids, and light intensity on the light stability of vitamin A and riboflavin in lowfat milk. J Dairy Sci 1986;69:2779-84. https://www.ncbi.nlm.nih.gov/pubmed/3805455?dopt=Abstract|
|34, 35, 36, 37.||↵||Mackey A, Davis S, Gregory J. Vitamin B6. In: Shils M, Shike M, Ross A, Caballero B, Cousins R, eds. Modern Nutrition in Health and Disease. 10th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2005.|
|38.||↵||McCormick D. Vitamin B6. In: Bowman B, Russell R, eds. Present Knowledge in Nutrition. 9th ed. Washington, DC: International Life Sciences Institute; 2006.|
|40.||↵||Herbert V. Vitamin B12 in Present Knowledge in Nutrition. 17th ed. Washington, DC: International Life Sciences Institute Press, 1996.|
|41.||↵||Herbert V, Das K. Vitamin B12 in Modern Nutrition in Health and Disease. 8th ed. Baltimore, MD: Williams & Wilkins, 1994.|
|42.||↵||Combs G. Vitamin B12 in The Vitamins. New York: Academic Press, Inc., 1992.|
|43.||↵||Zittoun J, Zittoun R. Modern clinical testing strategies in cobalamin and folate deficiency. Sem Hematol 1999;36:35-46. https://www.ncbi.nlm.nih.gov/pubmed/9930567?dopt=Abstract|
|44, 45, 46.||↵||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.|
|47.||↵||Klee GG. Cobalamin and folate evaluation: measurement of methylmalonic acid and homocysteine vs vitamin B(12) and folate. Clin Chem 2000;46:1277-83. https://www.ncbi.nlm.nih.gov/pubmed/10926922?dopt=Abstract|
|48.||↵||Carmel R. How I treat cobalamin (vitamin B12) deficiency. Blood.2008;112:2214-21. https://www.ncbi.nlm.nih.gov/pubmed/18606874?dopt=Abstract|
|50.||↵||U.S. National Library of Medicine, MedlinePlus – Folic Acid – https://medlineplus.gov/folicacid.html|
|51.||↵||Office on Women’s Health, U.S. Department of Health and Human Services – Folic acid – https://www.womenshealth.gov/a-z-topics/folic-acid|
|52.||↵||Centers for Disease Control and Prevention – Facts About Folic Acid – https://www.cdc.gov/ncbddd/folicacid/about.html|
|54.||↵||Naidu KA: Vitamin C in human health and disease is still a mystery? An overview. Nutr J 2: 7, 2003. https://www.ncbi.nlm.nih.gov/pubmed/14498993?dopt=Abstract|
|55, 59, 65.||↵||Li Y, Schellhorn HE. New developments and novel therapeutic perspectives for vitamin C. J Nutr 2007;137:2171-84. https://www.ncbi.nlm.nih.gov/pubmed/17884994?dopt=Abstract|
|56, 62, 63, 67.||↵||Jacob RA, Sotoudeh G. Vitamin C function and status in chronic disease. Nutr Clin Care 2002;5:66-74. https://www.ncbi.nlm.nih.gov/pubmed/12134712?dopt=Abstract|
|57.||↵||Merck Sharp & Dohme Corp., Merck Manual. Vitamin C (Ascorbic Acid). https://www.merckmanuals.com/professional/nutritional-disorders/vitamin-deficiency,-dependency,-and-toxicity/vitamin-c|
|58.||↵||National Cancer Institute. High-Dose Vitamin C–Patient Version. https://www.cancer.gov/about-cancer/treatment/cam/patient/vitamin-c-pdq#link/_5|
|60, 66.||↵||Carr AC, Frei B. Toward a new recommended dietary allowance for vitamin C based on antioxidant and health effects in humans. Am J Clin Nutr 1999;69:1086-107. https://www.ncbi.nlm.nih.gov/pubmed/10357726?dopt=Abstract|
|61.||↵||Proc Natl Acad Sci U S A. 1989 Aug;86(16):6377-81. Ascorbate is an outstanding antioxidant in human blood plasma. https://www.ncbi.nlm.nih.gov/pubmed/2762330%20?dopt=Abstract|
|64.||↵||Gershoff SN. Vitamin C (ascorbic acid): new roles, new requirements? Nutr Rev 1993;51:313-26. https://www.ncbi.nlm.nih.gov/pubmed/8108031?dopt=Abstract|
|68.||↵||Weinstein M, Babyn P, Zlotkin S. An orange a day keeps the doctor away: scurvy in the year 2000. Pediatrics 2001;108:E55. https://www.ncbi.nlm.nih.gov/pubmed/11533373?dopt=Abstract|
|69.||↵||Wang AH, Still C. Old world meets modern: a case report of scurvy. Nutr Clin Pract 2007;22:445-8. https://www.ncbi.nlm.nih.gov/pubmed/17644699?dopt=Abstract|
|70.||↵||Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. Washington, DC: National Academy Press, 2000. https://www.nap.edu/catalog/9810/dietary-reference-intakes-for-vitamin-c-vitamin-e-selenium-and-carotenoids|
|71.||↵||Stephen R, Utecht T. Scurvy identified in the emergency department: a case report. J Emerg Med 2001;21:235-7. https://www.ncbi.nlm.nih.gov/pubmed/11604276?dopt=Abstract|
|73.||↵||National Institute of Health. Vitamin D. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/|
|74, 75, 77, 78, 81.||↵||Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academy Press, 2010|
|76.||↵||Cranney C, Horsely T, O’Donnell S, Weiler H, Ooi D, Atkinson S, et al. Effectiveness and safety of vitamin D. Evidence Report/Technology Assessment No. 158 prepared by the University of Ottawa Evidence-based Practice Center under Contract No. 290-02.0021. AHRQ Publication No. 07-E013. Rockville, MD: Agency for Healthcare Research and Quality, 2007. https://www.ncbi.nlm.nih.gov/pubmed/18088161?dopt=Abstract|
|79.||↵||Holick MF. Vitamin D. In: Shils ME, Shike M, Ross AC, Caballero B, Cousins RJ, eds. Modern Nutrition in Health and Disease, 10th ed. Philadelphia: Lippincott Williams & Wilkins, 2006.|
|80.||↵||Norman AW, Henry HH. Vitamin D. In: Bowman BA, Russell RM, eds. Present Knowledge in Nutrition, 9th ed. Washington DC: ILSI Press, 2006.|
|83, 86.||↵||Traber MG. Vitamin E. In: Shils ME, Shike M, Ross AC, Caballero B, Cousins R, eds. Modern Nutrition in Health and Disease. 10th ed. Baltimore, MD: Lippincott Williams & Wilkins, 2006;396-411.|
|84.||↵||Merck Sharp & Dohme Corp., Merck Manual. Vitamin E (Tocopherol). https://www.merckmanuals.com/professional/nutritional-disorders/vitamin-deficiency,-dependency,-and-toxicity/vitamin-e|
|85.||↵||Verhagen H, Buijsse B, Jansen E, Bueno-de-Mesquita B. The state of antioxidant affairs. Nutr Today 2006;41:244-50.|
|87, 88.||↵||Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes: Vitamin C, Vitamin E, Selenium, and Carotenoids. Washington, DC: National Academy Press, 2000. https://www.nap.edu/catalog/9810/dietary-reference-intakes-for-vitamin-c-vitamin-e-selenium-and-carotenoids|
|90.||↵||U.S. National Library of Medicine. Medline Plus. Iron. https://medlineplus.gov/iron.html#cat_51|
|91.||↵||Centers for Disease Control and Prevention. Recommendations to Prevent and Control Iron Deficiency in the United States. https://www.cdc.gov/mmwr/preview/mmwrhtml/00051880.htm|
|92.||↵||U.S. National Library of Medicine. Iron. https://livertox.nlm.nih.gov/Iron.htm|
|93.||↵||Murray-Kolbe LE, Beard J. Iron. In: Coates PM, Betz JM, Blackman MR, et al., eds. Encyclopedia of Dietary Supplements. 2nd ed. London and New York: Informa Healthcare; 2010:432-8.|
|94.||↵||Aggett PJ. Iron. In: Erdman JW, Macdonald IA, Zeisel SH, eds. Present Knowledge in Nutrition. 10th ed. Washington, DC: Wiley-Blackwell; 2012:506-20.|
|95.||↵||Hurrell R, Egli I. Iron bioavailability and dietary reference values. Am J Clin Nutr 2010;91:1461S-7S. http://ajcn.nutrition.org/content/91/5/1461S.long|
|96.||↵||Rutzke CJ, Glahn RP, Rutzke MA, Welch RM, Langhans RW, Albright LD, et al. Bioavailability of iron from spinach using an in vitro/human Caco-2 cell bioassay model. Habitation 2004;10:7-14. https://www.ncbi.nlm.nih.gov/pubmed/15880905|
|98.||↵||Sunde RA. Selenium. In: Ross AC, Caballero B, Cousins RJ, Tucker KL, Ziegler TR, eds. Modern Nutrition in Health and Disease. 11th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2012:225-37|
|99.||↵||Sunde RA. Selenium. In: Bowman B, Russell R, eds. Present Knowledge in Nutrition. 9th ed. Washington, DC: International Life Sciences Institute; 2006:480-97|
|100.||↵||Terry EN, Diamond AM. Selenium. In: Erdman JW, Macdonald IA, Zeisel SH, eds. Present Knowledge in Nutrition. 10th ed. Washington, DC: Wiley-Blackwell; 2012:568-87|
|101.||↵||Environ Health Prev Med. 2008 Mar; 13(2): 102–108. Selenium: its role as antioxidant in human health. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2698273/|
|102.||↵||Br J Nutr. 2008 Aug;100(2):254-68. doi: 10.1017/S0007114508939830. Epub 2008 Mar 18. Food-chain selenium and human health: emphasis on intake. https://www.ncbi.nlm.nih.gov/pubmed/18346308?dopt=Abstract|
|103.||↵||Lancet. 2012 Mar 31;379(9822):1256-68. doi: 10.1016/S0140-6736(11)61452-9. Epub 2012 Feb 29. Selenium and human health. https://www.ncbi.nlm.nih.gov/pubmed/22381456?dopt=Abstract|
|106.||↵||Sandstead HH. Understanding zinc: recent observations and interpretations. J Lab Clin Med 1994;124:322-7. https://www.ncbi.nlm.nih.gov/pubmed/8083574?dopt=Abstract|
|107, 112.||↵||Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc (2001). Washington, DC: National Academy Press, 2001. https://www.nap.edu/catalog/10026/dietary-reference-intakes-for-vitamin-a-vitamin-k-arsenic-boron-chromium-copper-iodine-iron-manganese-molybdenum-nickel-silicon-vanadium-and-zinc|
|108.||↵||Solomons NW. Mild human zinc deficiency produces an imbalance between cell-mediated and humoral immunity. Nutr Rev 1998;56:27-8. https://www.ncbi.nlm.nih.gov/pubmed/9481116?dopt=Abstract|
|109, 110, 113, 114.||↵||Prasad AS. Zinc: an overview. Nutrition 1995;11:93-9. https://www.ncbi.nlm.nih.gov/pubmed/7749260?dopt=Abstract|
|111.||↵||Heyneman CA. Zinc deficiency and taste disorders. Ann Pharmacother 1996;30:186-7. https://www.ncbi.nlm.nih.gov/pubmed/8835055?dopt=Abstract|
|115.||↵||Simmer K, Thompson RP. Zinc in the fetus and newborn. Acta Paediatr Scand Suppl 1985;319:158-63. https://www.ncbi.nlm.nih.gov/pubmed/3868917?dopt=Abstract|
|116.||↵||Fabris N, Mocchegiani E. Zinc, human diseases and aging. Aging (Milano) 1995;7:77-93. https://www.ncbi.nlm.nih.gov/pubmed/7548268?dopt=Abstract|
|117.||↵||Maret W, Sandstead HH. Zinc requirements and the risks and benefits of zinc supplementation. J Trace Elem Med Biol 2006;20:3-18. https://www.ncbi.nlm.nih.gov/pubmed/16632171?dopt=Abstract|
|118.||↵||Prasad AS, Beck FW, Grabowski SM, Kaplan J, Mathog RH. Zinc deficiency: changes in cytokine production and T-cell subpopulations in patients with head and neck cancer and in noncancer subjects. Proc Assoc Am Physicians 1997;109:68-77. https://www.ncbi.nlm.nih.gov/pubmed/9010918?dopt=Abstract|
|119.||↵||Rink L, Gabriel P. Zinc and the immune system. Proc Nutr Soc 2000;59:541-52. https://www.ncbi.nlm.nih.gov/pubmed/11115789?dopt=Abstract|