Other name(s):

vitamin B-9, folacin, folate, tetrahydrofolic acid, tetrahydropteroylglutamic acid, THF

General description

Folic acid is a water-soluble vitamin. It is the supplemental form of folate, also called vitamin B-9. It is an important part of cell division and in making cells in some organs and bone marrow. It also helps a baby’s spinal cord to grow and develop in the womb. Like the other B vitamins, folic acid helps make energy in your body.

The body converts folic acid to tetrahydrofolic acid. This acid is an important part of cell division. It helps make nucleic acid (DNA and RNA).

Folic acid deficiency causes some red blood cells to be larger than normal. This is called macrocytic anemia. This also causes other problems in white and red blood cells.

Medically valid uses

Folic acid is used to prevent or treat folic acid deficiencies. Folic acid can reduce the risk of neural tube defects (spina bifida) in newborn babies. For this reason, women of childbearing age should take at least 400 micrograms (mcg) of folic acid daily. It should be taken every day. Start at least 1 month before trying to get pregnant.

Studies suggest that taking folic acid alone or with other B-vitamins reduces the risk for stroke.

Unsubstantiated claims

There may be benefits that have not yet been proven through research.

Folic acid may help treat uterine cervical dysplasia. It may also boost the immune system and help treat depression.

Folic acid supplements haven’t been shown to affect heart disease. 

Recommended intake

Folic acid is measured in micrograms (mcg). The RDA is the Recommended Dietary Allowance.

Since 1998, the FDA has required food manufacturers to add folic acid to breads, cereals, flours, cornmeal, pastas, rice, and other grains. For other foods, check the Nutrition Facts label on the package to see if it has folic acid. The label will also tell you how much folic acid is in each serving. The label may say “folate” instead of folic acid.

Between 50% and 95% of folic acid may be destroyed with cooking. For instance, 100 g of raw lima beans has 130 mcg of folic acid. But 100 g of canned lima beans (drained) has only 13 mcg. This is just 1/10 of the original amount.

Folic acid is destroyed by light. It’s also easily broken down in open air. You should store it in a light-resistant, airtight container. Keep it at room temperature.

Healthy people rarely have folic acid deficiency. But people with any of these conditions may have more need for folic acid:

• Malabsorption syndromes, such as lactose intolerance, celiac sprue, and cystic fibrosis

• Inflammatory bowel disease, such as Crohn’s disease and ulcerative colitis

• Chronic hemolytic anemia, such as sickle cell anemia, G6PD deficiency, or thalassemia 

• Surgery to remove the jejunum, a part of the small intestine

• Cancer

• Hemochromatosis

• Underactive thyroid (hypothyroidism)

• Dialysis

• Moderate to heavy alcohol use

• People taking methotrexate

Women who are pregnant or breastfeeding may need to take supplements. Talk to your healthcare provider before doing so. Prescribed and over-the-counter prenatal vitamins have different amounts of folic acid.

If you have a folic acid deficiency, you have a reduced number of white blood cells. The nuclei of the white cells have too many lobes (hypersegmentation).

Symptoms of folic acid deficiency include:

• Swelling of your tongue

• Diarrhea

• Fatigue

• Irritability

• A slight decrease in mental function

Side effects, toxicity, and interactions

There are no known side effects linked with large doses of folic acid. But very large doses may cause kidney damage. High doses may also cause a loss of appetite.

Don’t take folic acid if you have untreated pernicious anemia unless your healthcare provider tells you to do so. High doses of folic acid can hide pernicious anemia, which is due to vitamin B-12 deficiency. Your healthcare provider may watch you closely if you have vitamin B-12 deficiency and you also need folic acid supplements. 

Many medicines affect folic acid. This raises your need for extra doses of folic acid. These include:

• Oral birth control pills

• Pentamidine

• Trimethoprim

• Triamterene

• Pyrimethamine

• Medicines for seizures, such as phenytoin, primidone, and phenobarbital

Some cancers are treated with folic acid antagonists. These are medicines that block the function of folic acid. You shouldn’t take folic acid supplements while you’re on chemotherapy unless your healthcare provider tells you to do so.