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 ².

Folate functions as a coenzyme or cosubstrate in single-carbon transfers in the synthesis of nucleic acids (DNA and RNA) and metabolism of amino acids ³. One of the most important folate-dependent reactions is the conversion of homocysteine to methionine in the synthesis of S-adenosyl-methionine, an important methyl donor ³. Another folate-dependent reaction, the methylation of deoxyuridylate to thymidylate in the formation of DNA, is required for proper cell division. An impairment of this reaction initiates a process that can lead to megaloblastic anemia, one of the hallmarks of folate deficiency ⁴.

When consumed, food folates are hydrolyzed to the monoglutamate form in the gut prior to absorption by active transport across the intestinal mucosa ⁵. Passive diffusion also occurs when pharmacological doses of folic acid are consumed ⁵. Before entering the bloodstream, the monoglutamate form is reduced to tetrahydrofolate (THF) and converted to either methyl or formyl forms. The main form of folate in plasma is 5-methyl-THF. Folic acid can also be found in the blood unaltered (known as unmetabolized folic acid), but whether this form has any biological activity or can be used as a biomarker of status is not known ⁶.

The total body content of folate is estimated to be 10 to 30 mg; about half of this amount is stored in the liver and the remainder in blood and body tissues. A serum folate concentration is commonly used to assess folate status, with a value above 3 nanograms (ng)/mL indicating adequacy ⁴. This indicator, however, is sensitive to recent dietary intake, so it might not reflect long-term status. Erythrocyte folate concentration provides a longer-term measure of folate intakes, so when day-to-day folate intakes are variable—such as in people who are ill and whose folate intake has recently declined—it might be a better indicator of tissue folate stores than serum folate concentration ⁵. An erythrocyte folate concentration above 140 ng/mL indicates adequate folate status ⁵, although some researchers have suggested that higher values are optimal for preventing neural tube defects ⁷.

A combination of serum or erythrocyte concentration and indicators of metabolic function can also be used to assess folate status. Plasma homocysteine concentration is a commonly used functional indicator of folate status because homocysteine levels rise when the body cannot convert homocysteine to methionine due to a 5-methyl-THF deficiency. Homocysteine levels, however, are not a highly specific indicator of folate status because they can be influenced by other factors, including kidney dysfunction and deficiencies of vitamin B12 and other micronutrients ⁸. The most commonly used cutoff value for elevated homocysteine is 16 micromoles/L, although slightly lower values of 12 to 14 micromoles/L have also been used ⁵.

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.

The symptoms of folate-deficiency anemia include:

Fatigue
Headache
Pale skin
Sore mouth and tongue

If you have folate-deficiency anemia, your doctor may recommend taking folic acid vitamins and eating more foods with folate.

Why is Folic Acid Important ?

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 ⁹).

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.

Why do women need folic acid ?

Everyone needs folic acid to be healthy. But it is especially important for women:

Before and during pregnancy. Folic acid protects unborn children against serious birth defects called neural tube defects. These birth defects happen in the first few weeks of pregnancy, often before a woman knows she is pregnant. Folic acid might also help prevent other types of birth defects and early pregnancy loss (miscarriage). Since about half of all pregnancies in the United States are unplanned ¹⁰, experts recommend all women get enough folic acid even if you are not trying to get pregnant.

To keep the blood healthy by helping red blood cells form and grow. Not getting enough folic acid can lead to a type of anemia called folate-deficiency anemia. Folate-deficiency anemia is more common in women of childbearing age than in men.

Do Women need to take Folic Acid every day even if you’re not planning to get pregnant ?

Yes. All women who can get pregnant need to take 400 to 800 micrograms of folic acid every day, even if you’re not planning to get pregnant ¹¹. There are several reasons why:

Your birth control may not work or you may not use birth control correctly every time you have sex. In a survey by the Centers for Disease Control and Prevention, almost 40% of women with unplanned pregnancies were using birth control ¹².
Birth defects of the brain and spine can happen in the first few weeks of pregnancy, often before you know you are pregnant. By the time you find out you are pregnant, it might be too late to prevent the birth defects.
You need to take folic acid every day because it is a water soluble B-vitamin. Water soluble means that it does not stay in the body for a long time. Your body metabolizes (uses) folic acid quickly, so your body needs folic acid each day to work properly.

What can happen if Women do Not get enough Folic Acid during Pregnancy ?

If you do not get enough folic acid before and during pregnancy, your baby is at higher risk for neural tube defects.

Neural tube defects are serious birth defects that affect the spine, spinal cord, or brain and may cause death. These include:

Spina bifida ¹³. This condition happens when an unborn baby’s spinal column does not fully close during development in the womb, leaving the spinal cord exposed. As a result, the nerves that control the legs and other organs do not work. Children with spina bifida often have lifelong disabilities. They may also need many surgeries.
Anencephaly ¹⁴. This means that most or all of the brain and skull does not develop in the womb. Almost all babies with this condition die before or soon after birth.

How much Folic Acid do Women need ?

All women need 400 micrograms of folic acid every day. Women who can get pregnant should get 400 to 800 micrograms of folic acid from a vitamin or from food that has added folic acid, such as breakfast cereal ¹⁵. This is in addition to the folate you get naturally from food.

Some women may need more folic acid each day. See the chart to find out how much folic acid you need.

If you:	Amount of folic acid you may need daily^¹⁵
Could get pregnant or are pregnant	400–800 micrograms.¹⁵ Your doctor may prescribe a prenatal vitamin with more.
Had a baby with a neural tube defect (such as spina bifida) and want to get pregnant again	4,000 micrograms. Your doctor may prescribe this amount. Research shows taking this amount may lower the risk of having another baby with spina bifida. ¹⁶
Have a family member with spina bifida and could get pregnant	4,000 micrograms. Your doctor may prescribe this amount.
Have spina bifida and want to get pregnant	4,000 micrograms. Your doctor may prescribe this amount. Women with spina bifida have a higher risk of having children with the condition.
Take medicines to treat epilepsy, type 2 diabetes, rheumatoid arthritis, or lupus	Talk to your doctor or nurse. Folic acid supplements can interact with these medicines.
Are on dialysis for kidney disease	Talk to your doctor or nurse.
Have a health condition, such as inflammatory bowel disease or celiac disease, that affects how your body absorbs folic acid	Talk to your doctor or nurse.

How can you be sure you get enough folic acid ?

You can get enough folic acid from food alone. Many breakfast cereals have 100% of your recommended daily value (400 micrograms) of folic acid.

If you are at risk for not getting enough folic acid, your doctor may recommend that you take a vitamin with folic acid every day. Most U.S. multivitamins have at least 400 micrograms of folic acid. Check the label on the bottle to be sure. You can also take a pill that contains only folic acid.

If swallowing pills is hard for you, try a chewable or liquid product with folic acid.

Are some women at risk for not getting enough folic acid ?

Yes, certain groups of women do not get enough folic acid each day ¹⁷.

Women who can get pregnant need more folic acid (400 to 800 micrograms). ¹⁶
Nearly one in three African-American women does not get enough folic acid each day.
Spanish-speaking Mexican-American women often do not get enough folic acid. However, Mexican-Americans who speak English usually get enough folic acid. ¹⁸

Not getting enough folic acid can cause health problems, including folate-deficiency anemia, and problems during pregnancy for you and your unborn baby.

How a Woman can get enough Folic Acid

There are two easy ways to be sure to get enough folic acid each day:

Take a vitamin that has folic acid in it every day. Most multivitamins sold in the United States have the amount of folic acid women need each day. Women can also choose to take a small pill (supplement) that has only folic acid in it each day.
Multivitamins and folic acid pills can be found at most local pharmacy, grocery, or discount stores.
Check the label to be sure it contains 100% of the daily value (DV) of folic acid, which is 400 micrograms (mcg).
Eat a bowl of breakfast cereal that has 100% of the daily value of folic acid every day.

Not every cereal has this amount. Make sure you check the label on the side of the box, and look for one that has “100%” next to folic acid or 400 micrograms (mcg).

How much folate do you need ?

The amount of folate you need depends on your age. Average daily recommended amounts are listed below in micrograms (mcg) of dietary folate equivalents (DFEs).

All women and teen girls who could become pregnant should consume 400 mcg of folic acid daily from supplements, fortified foods, or both in addition to the folate they get naturally from foods.

Table 1: Recommended Dietary Allowances (RDAs) for Folate

Life Stage	Recommended Amount
Birth to 6 months*	65 mcg DFE*
Infants 7–12 months*	80 mcg DFE*
Children 1–3 years	150 mcg DFE
Children 4–8 years	200 mcg DFE
Children 9–13 years	300 mcg DFE
Teens 14–18 years	400 mcg DFE
Adults 19–50 years	400 mcg DFE
Adults 51–70 years	400 mcg DFE
Adults 71+ years	400 mcg DFE
Pregnant teens and women	600 mcg DFE
Breastfeeding teens and women	500 mcg DFE

* Adequate Intake (AI)

[Source ⁵]

Do you need folic acid after menopause ?

Yes. Women who have gone through menopause still need 400 micrograms of folic acid every day for good health. Talk to your doctor or nurse about how much folic acid you need.

What foods provide folate ?

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.

In January 1998, the U.S. Food and Drug Administration (FDA) began requiring manufacturers to add folic acid to enriched breads, cereals, flours, cornmeals, pastas, rice, and other grain products ¹⁹. Because cereals and grains are widely consumed in the United States, these products have become very important contributors of folic acid to the American diet. The fortification program was projected to increase folic acid intakes by approximately 100 mcg/day ²⁰, but the program actually increased mean folic acid intakes in the United States by about 190 mcg/day ²¹. In April 2016, FDA approved the voluntary addition of folic acid to corn masa flour at levels consistent with other enriched grain products ²².

The Canadian government has also required the addition of folic acid to many grains, including white flour, enriched pasta, and cornmeal, since November 1, 1998 ²³. Other countries, including Costa Rica, Chile, and South Africa, have also established mandatory folic acid fortification programs ²⁴.

Table 2. Selected Food Sources of Folate and Folic Acid

Food	mcg DFE per serving	Percent DV*
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 ²⁵]

Can Food Alone Provide You with Enough Folate ?

Yes, many people get enough folic acid from food alone. Some foods have high amounts of folic acid. For example, many breakfast cereals have 100% of the recommended daily value (400 micrograms) of folic acid in each serving. Check the label to be sure.

Some women, especially women who could get pregnant, may not get enough folic acid from food. African-American women and Mexican Americans are also at higher risk for not getting enough folic acid each day. Talk to your doctor or nurse about whether you should take a vitamin to get the 400 micrograms of folic acid you need each day. (source ²).

What should you look for when buying Vitamin Supplement with Folic Acid ?

Look for “USP” or “NSF” on the label when choosing vitamins. These “seals of approval” mean the pills are made properly and have the amounts of vitamins it says on the label. Also, make sure the pills have not expired. If the bottle has no expiration date, do not buy it.

Ask your pharmacist for help with selecting a vitamin or folic acid-only pill. If you are pregnant and already take a daily prenatal vitamin, you probably get all the folic acid you need. Check the label to be sure.
Vitamin label

Check the “Supplement Facts” label to be sure you are getting 400 to 800 micrograms (mcg) of folic acid. (source ¹⁵).

Are you getting enough folate ?

Most people in the United States get enough folate. However, certain groups of people are more likely than others to have trouble getting enough folate:

Teen girls and women aged 14–30 years (especially before and during pregnancy).
Non-Hispanic black women.
People with disorders that lower nutrient absorption (such as celiac disease and inflammatory bowel disease).
People with alcoholism.

What happens if you don’t get enough folate ?

Folate deficiency is rare in the United States, but some people get barely enough. Getting too little folate can result in megaloblastic anemia, which causes weakness, fatigue, trouble concentrating, irritability, headache, heart palpitations, and shortness of breath. Folate deficiency can also cause open sores on the tongue and inside the mouth as well as changes in the color of the skin, hair, or fingernails.

Women who don’t get enough folate are at risk of having babies with neural tube defects, such as spina bifida. Folate deficiency can also increase the likelihood of having a premature or low-birth-weight baby.

What are some effects of folate on health ?

Scientists are studying folate to understand how it affects health. Here are several examples of what this research has shown.

Neural tube defects
Taking folic acid regularly before becoming pregnant and during early pregnancy helps prevent neural tube defects in babies. But about half of all pregnancies are unplanned. Therefore, all women and teen girls who could become pregnant should consume 400 mcg of folic acid daily from supplements, fortified foods, or both in addition to the folate they get naturally from foods.Since 1998, the U.S. Food and Drug Administration has required food companies to add folic acid to enriched bread, cereal, flour, cornmeal, pasta, rice, and other grain products sold in the United States. Because most people in the United States eat these foods on a regular basis, folic acid intakes have increased and the number of babies born with neural tube defects has decreased since 1998.
Preterm birth, congenital heart defects, and other birth defects
Taking folic acid might reduce the risk of having a premature baby and prevent birth defects, such as congenital heart problems. But more research is needed to understand how folic acid affects the risk of these conditions.
Cancer
Folate that is found naturally in food may decrease the risk of several forms of cancer. But folate might have different effects depending on how much is taken and when. Modest amounts of folic acid taken before cancer develops might decrease cancer risk, but high doses taken after cancer (especially colorectal cancer) begins might speed up its progression. For this reason, high doses of folic acid supplements (more than the upper limit of 1,000 mcg) should be taken with caution, especially by people who have a history of colorectal adenomas (which sometimes turn into cancer). More research is needed to understand the roles of dietary folate and folic acid supplements in cancer risk.
Heart disease and stroke
Some scientists used to think that folic acid and other B-vitamins might reduce heart disease risk by lowering levels of homocysteine, an amino acid in the blood. But although folic acid supplements do lower blood homocysteine levels, they don’t decrease the risk of heart disease. Some studies have shown that a combination of folic acid with other B-vitamins, however, helps prevent stroke.
Dementia, cognitive function, and Alzheimer’s disease
Folic acid supplements with or without other B-vitamins do not seem to improve cognitive function, but more research on this topic is needed.
Depression
People with low blood levels of folate might be more likely to suffer from depression and might not respond as well to treatment with antidepressants as people with normal folate levels.Folic acid supplements might make antidepressant medications more effective. But it is not clear whether these supplements help people with both normal folate levels and those with folate deficiency. More research is needed to learn about the role of folate in depression and whether folic acid supplements are helpful when used in combination with standard treatment.

Can folate be harmful ?

Folate that is naturally present in food is not harmful. Folic acid in supplements and fortified foods, however, should not be consumed in amounts above the upper limit, unless recommended by a health care provider.

Taking large amounts of folic acid might hide a vitamin B12 deficiency. Folic acid can correct the anemia but not the nerve damage caused by vitamin B12 deficiency. This can lead to permanent damage of the brain, spinal cord, and nerves. High doses of folic acid might also increase the risk of colorectal cancer and possibly other cancers in some people.

Can you get too much folic acid ?

Yes, you can get too much folic acid, but only from man-made products such as multivitamins and fortified foods, such as breakfast cereals. You can’t get too much from foods that naturally contain folate.

You should not get more than 1,000 micrograms of folic acid a day, unless your doctor prescribes a higher amount. Too much folic acid can hide signs that you lack vitamin B12, which can cause nerve damage. (source ²⁶).

References

U.S. National Library of Medicine, MedlinePlus – Folic Acid – https://medlineplus.gov/folicacid.html
Office on Women’s Health, U.S. Department of Health and Human Services – Folic acid – https://www.womenshealth.gov/a-z-topics/folic-acid
Bailey LB, Gregory JFr (2006). Folate. Present Knowledge in Nutrition. B. Bowman and R. Russell. Washington, DC, International Life Sciences Institute. I: 278-301.
Carmel R (2005). Folic Acid. Modern Nutrition in Health and Disease. M. Shils, M. Shike, A. Ross, B. Caballero and R. Cousins. Baltimore, MD, Lippincott Williams & Wilkins: 470-481.
Institute of Medicine. Food and Nutrition Board (1998). Dietary Reference Intakes: Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC, National Academy Press. https://www.nap.edu/catalog/6015/dietary-reference-intakes-for-thiamin-riboflavin-niacin-vitamin-b6-folate-vitamin-b12-pantothenic-acid-biotin-and-choline
Yetley EA, Pfeiffer CM, Phinney KW, Fazili Z, Lacher DA, Bailey RL, et al. (2011). Biomarkers of folate status in NHANES: a roundtable summary. Am J Clin Nutr 94(1): 303S-312S. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3127517/
Colapinto CK, O’Connor DL, Dubois L, Tremblay MS (2012). Folic acid supplement use is the most significant predictor of folate concentrations in Canadian women of childbearing age. Appl Physiol Nutr Metab 37(2): 284-292. http://www.nrcresearchpress.com/doi/full/10.1139/h11-161
Green R (2011). Indicators for assessing folate and vitamin B-12 status and for monitoring the efficacy of intervention strategies. Am J Clin Nutr 94(2): 666S-672S. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3142735/
Centers for Disease Control and Prevention – Facts About Folic Acid – https://www.cdc.gov/ncbddd/folicacid/about.html
Finer, L.B., Zolna, M.R. (2016). Declines in unintended pregnancy in the United States, 2008-2011. The New England Journal of Medicine; 374(9):843–52.
U.S. Preventive Services Task Force. (2016). Final Recommendation Statement: Folic Acid for the Prevention of Neural Tube Defects: Preventive Medication – https://www.uspreventiveservicestaskforce.org/Page/Document/RecommendationStatementFinal/folic-acid-for-the-prevention-of-neural-tube-defects-preventive-medication
Mosher, W.D., Jones, J., Abma, J.C. (2012). Intended and Unintended Births in the United States: 1982–2010 (PDF, 404 KB). National Health Statistics Reports; no. 55.
CDC. (2016). Spina Bifida. – https://www.cdc.gov/ncbddd/spinabifida/facts.html
CDC. (2015). Facts about Anencephaly. – https://www.cdc.gov/ncbddd/birthdefects/anencephaly.html
U.S. Preventive Services Task Force. (2016). Final Recommendation Statement: Folic Acid for the Prevention of Neural Tube Defects: Preventive Medication
CDC. (2016). Folic Acid Recommendations.- https://www.cdc.gov/ncbddd/folicacid/recommendations.html
Bailey, R.L., Dodd, K.W., Gahche, J.J., Dwyer, J.T., McDowell, M.A., Yetley, E.A., et al. (2010). Total folate and folic acid intake from foods and dietary supplements in the United States: 2003–2006. American Journal of Clinical Nutrition; 91(1): 231–237.
Hamner, H.C., Cogswell, M.E., Johnson, M.A. (2011). Acculturation factors are associated with folate intakes among Mexican American women. The Journal of Nutrition; 141(10): 1889–97.
U.S. Food and Drug Administration (1996). Food standards: amendment of standards of identity for enriched grain products to require addition of folic acid. Federal Register 61(44). https://www.gpo.gov/fdsys/pkg/FR-1996-03-05/pdf/96-5014.pdf
Whittaker P, Tufaro PR, Rader JI (2001). Iron and folate in fortified cereals. J Am Coll Nutr 20(3): 247-254. https://www.ncbi.nlm.nih.gov/pubmed/11444421
Choumenkovitch SF, Selhub J, Wilson PW, Rader JI, Rosenberg IH Jacques PF (2002). Folic acid intake from fortification in United States exceeds predictions. J Nutr 132(9): 2792-2798. http://jn.nutrition.org/content/132/9/2792.long
Food and Drug Administration. Final rule: food additives permitted for direct addition to food for human consumption; folic acid. Federal Register 81(73):22176-22183, April 15, 2016. https://www.federalregister.gov/documents/2016/04/15/2016-08792/food-additives-permitted-for-direct-addition-to-food-for-human-consumption-folic-acid
Government of Canada (1998). Regulations Amending the Food and Drug Regulations (1066). Canada Gazette 132(24).
Centers for Disease Control and Prevention (2010). CDC Grand Rounds: additional opportunities to prevent neural tube defects with folic acid fortification. MMWR Morb Mortal Wkly Rep 59(31): 980-984. https://www.cdc.gov/mmwr/preview/mmwrhtml/mm5931a2.htm
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/
Morris, M.S., Jacques, P.F., Rosenberg, I.H., et al. (2007). Folate and vitamin B12 status in relation to anemia, macrocytosis and cognitive impairment in older Americans in the age of folic acid fortification. Am J Clin Nutr; 85(1):193–200.

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