Birth defects prevention
Gingivitis (periodontal disease) (rinse only)
High homocysteine (in combination with vitamin B6 and vitamin B12)
Pap smear (abnormal) (in women taking oral contraceptives)
Pregnancy and postpartum support
Schizophrenia (for deficiency)
Anemia (for thalassemia if deficient)
Breast cancer (reduces risk in women who consume alcohol)
Canker sores (for deficiency only)
Celiac disease (for deficiency only)
Colon cancer (prevention)
Sickle cell anemia (for lowering homocysteine levels)
Bipolar Disorder/Manic Depression
Dermatitis herpetiformis (for deficiency)
Gingivitis (periodontal disease) (pill)
Lung cancer (reduces risk)
Peripheral vascular disease
Restless legs syndrome
Stroke (for high homocysteine only)
Reliable and relatively consistent scientific data showing a substantial health benefit.
Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support and/or minimal health benefit.
Who is likely to be deficient of folic acid?
Many people consume less than the recommended amount of folic acid. Scientists have found that people with heart disease commonly have elevated blood levels of homocysteine, a laboratory test abnormality often controllable with folic acid supplements. This suggests that many people in Western societies have a mild folic acid deficiency. In fact, it has been suggested that increasing folic acid intake could prevent an estimated 13,500 deaths from cardiovascular diseases each year.29
Folic acid deficiency has also been common in alcoholics, people living at poverty level, those with malabsorption disorders or liver disease (e.g., cirrhosis), and women taking the birth control pill. Recently, elderly people with hearing loss have been reported to be much more likely to be folic acid deficient than healthy elderly people.30 A variety of prescription drugs including cimetidine, antacids, some anticancer drugs, triamterene, sulfasalazine, and anticonvulsants interfere with folic acid.
Deficiency of folic acid can be precipitated by situations wherein the body requires greater than normal amounts of the vitamin, such as pregnancy, infancy, leukemia, exfoliative dermatitis, and diseases that cause the destruction of blood cells.31
The relationship between folic acid and prevention of neural tube defects is partly thought to result from the high incidence of folate deficiency in many societies. To protect against neural tube defects, the U.S. Food and Drug Administration has mandated that some grain products provide supplemental folic acid at a level expected to increase the dietary intake by an average of 100 mcg per day per person. As a result of folic acid added to the food supply, fewer Americans will be depleted compared with the past. In 1999, scientific evidence began to demonstrate that the folic acid added to the U.S. food supply was having positive effects, including a partial lowering of homocysteine levels.32 In the same year, however, a report from the North Carolina Birth Defects Monitoring Program suggested the current level of folic acid fortification has not reduced the incidence of neural-tube defects.33 Many doctors and the Centers for Disease Control in Atlanta34 believe that optimal levels of folic acid intake may still be higher than the amount now being added to food by several hundred micrograms per day. A low blood level of folate has also been associated with an increased risk of miscarriage.35
People with kidney failure have an increased risk of folic acid deficiency.36 Recipients of kidney transplants often have elevated homocysteine levels, which may respond to supplementation with folic acid.37 The usual recommended amount of 400 mcg per day may not be enough for these people, however. Larger amounts (up to 2.4 mg per day) may produce a better outcome, according to one double-blind trial.38
Folate deficiency is more prevalent among elderly African American women than among elderly white women.39
Which form is best?
Folic acid naturally found in food is much less available to the body compared with synthetic folic acid found both in supplements and added to grain products in the United States. Women with a recent history of giving birth to babies with neural tube defects participated in a study to determine which form of folic acid is best absorbed—dietary folic acid or folic acid from supplements.40 They received either orange juice containing 400 mcg of folic acid per day or a supplement containing the same amount. Overall, the supplement folic acid was better absorbed than the folic acid from orange juice.
How much folic acid is usually taken?
Many doctors recommend that all women who are or who could become pregnant take 400 mcg per day in order to reduce the risk of birth defects. Some doctors also extend this recommendation to other people in an attempt to reduce the risk of heart disease by lowering homocysteine levels. Since the FDA mandated addition of folic acid to grain products, many people who eat grains have followed the new recommendation of supplementing only 100 mcg of folic acid per day. However, studies have found that this amount of folic acid is inadequate to maintain normal folate levels in a significant percentage of the groups assessed.41 It now appears that, for pregnant women, supplementing with at least 300 mcg (and optimally 400 mcg) of folic acid per day is sufficient to prevent a folate deficiency, even if dietary intake is low.
Are there any side effects or interactions with folic acid?
Folic acid is not generally associated with side effects.42 However, folic acid supplementation can interfere with the laboratory diagnosis of vitamin B12 deficiency, possibly allowing the deficiency to progress undetected to the point of irreversible nerve damage.43 Although vitamin B12 deficiency is uncommon, no one should supplement with 1,000 mcg or more of folic acid without consulting a doctor.
Vitamin B12 deficiencies often occur without anemia (even in people who do not take folic acid supplements). Some doctors do not know that the absence of anemia does not rule out a B12 deficiency. If this confusion delays diagnosis of a vitamin B12 deficiency, the patient could be injured, sometimes permanently. This problem is rare and should not happen with doctors knowledgeable in this area using correct testing procedures.
Folic acid is needed by the body to utilize vitamin B12. Proteolytic enzymes inhibit folic acid absorption.44 People taking proteolytic enzymes are advised to supplement with folic acid.
Are there any drug interactions?
Certain medicines may interact with folic acid. Refer to drug interactions for a list of those medicines