Folic Acid

Other name(s):

vitamin B₉, folacin, folate, tetrahydrofolic acid, tetrahydropteroylglutamic acid, THF

General description

Folic acid, folate, or vitamin B₉, is a water-soluble vitamin. It plays an important part in cell division, in the creation of cells in the blood-forming organs and bone marrow, and in the proper development of the fetal spinal cord during pregnancy. Like the other B vitamins, folic acid plays an important role in energy production.

The body converts folic acid to tetrahydrofolic acid. Tetrahydrofolic acid plays an important part in cell division and is intimately involved in nucleic acid (DNA and RNA) synthesis.

Folic acid deficiency results in macrocytic anemia (larger-than-normal red blood cells and other abnormalities in white and red blood cells).

Research by the National Institutes of Health and the CDC suggests that folic acid supplements can reduce the incidence of neural tube defects (spina bifida) in newborn infants by up to 50 percent. Subsequently, they have recommended that women of childbearing age receive a minimum of 400 micrograms (mcg) of folic acid daily. To be effective, these requirements must be met on a daily basis, starting at least three months before becoming pregnant.

According to the American Heart Association (AHA), folic acid supplements have not been shown in controlled trials to affect the development or recurrence of cardiovascular disease. At this time, the AHA does not recommend the use of folic acid or vitamin B supplements to reduce the risk for cardiovascular disease.

Medically valid uses

Folic acid is used to prevent or treat folic acid deficiencies. Folic acid supplementation in women of childbearing age and pregnant mothers can reduce the risk for neural tube defects in newborns by 50 percent.

Unsubstantiated claims

Please note that this section reports on claims that have NOT yet been substantiated through scientific studies.

Claims about the benefits of folic acid include that it is useful in treating uterine cervical dysplasia (as indicated by abnormal pap smears), improving the immune system, and helping with depression.

Recommended intake

As indicated below, folic acid is measured in micrograms (mcg).  The RDA is the Recommended Dietary Allowance.

Between 50 and 95 percent of folic acid may be destroyed in the cooking process. For instance, 100 g of raw lima beans contain 130 mcg of folic acid, while 100 g of canned lima beans (drained) contain only 13 mcg—only one-tenth of the raw, unprocessed product.

Folic acid is unstable in light and easily oxidized in open air. As a result, it should be stored in a light-resistant, airtight container at room temperature.

Healthy people seldom experience overt folic acid deficiency. However, deficiencies can result from improper diet or a malabsorption syndrome. People suffering from chronic hemolytic anemias, including sickle cell anemia, G6PD deficiency or thalassemia, may need folic acid supplements. Other conditions that increase the need for folic acid include malabsorption syndromes (common with lactose intolerance, celiac sprue, or cystic fibrosis), inflammatory bowel disease (Crohn's disease or ulcerative colitis), surgical removal of the jejunum (a portion of the small intestine), malignancy (cancer), hemochromatosis, hypothyroidism (under-active thyroid gland), kidney dialysis, and moderate to heavy alcohol use.

Women who are pregnant or breastfeeding may need to take vitamin supplements, but must consult a physician before doing so. An increased amount of folic acid is what distinguishes prescription prenatal vitamins from their over-the-counter cousins.

The primary disease associated with folic acid deficiency is megaloblastic anemia. In this condition, the red blood cells are enlarged (macrocytic), but usually have normal amounts of hemoglobin inside (normochromic).

When folic acid is deficient, the number of white blood cells is reduced and often the nuclei of white cells have excessive numbers of lobes (hypersegmentation).

Symptoms associated with folic acid deficiency include glossitis (inflammation of the tongue), gastrointestinal disturbances such as diarrhea, fatigue, irritability, and a slight decrease in mental function.

Side effects, toxicity, and interactions

There are no known side effects associated with large doses of folic acid. However, excessively large dosages may cause damage to the kidneys from crystal formation. High doses may also cause a loss of appetite.

Do not take folic acid supplements during chemotherapy except at the advice of the treating physician.

Do not take folic acid without physician supervision if you have undiagnosed or untreated pernicious anemia. High doses of folic acid can mask pernicious anemia, which is due to vitamin B₁₂ deficiency. Close monitoring may be necessary for people who are at risk for vitamin B₁₂ deficiency, but also require folic acid supplements. 

Many drugs affect folic acid, increasing the need for supplemental doses of vitamin B₉. These drugs include oral contraceptives and certain prescription drugs such as pentamidine, trimethoprim, triamterene, and pyrimethamine. Also, the use of certain anti-seizure drugs, such as phenytoin, primidone, or phenobarbital, may require folic acid supplements.

Some cancers are treated with folic acid antagonists (agents that block the function of folic acid). No folic acid supplements should be taken during chemotherapy except at the advice of the treating physician.

Additional information

Click here for a list of reputable websites with general information on nutrition.