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Folic acid

What is it?

Folic acid is a water-soluble B vitamin. Since 1998, it has been added to cold cereals, flour, breads, pasta, bakery items, cookies, and crackers, as required by federal law. Foods that are naturally high in folic acid include leafy vegetables (such as spinach, broccoli, and lettuce), okra, asparagus, fruits (such as bananas, melons, and lemons) beans, yeast, mushrooms, meat (such as beef liver and kidney), orange juice, and tomato juice.

Folic acid is used for preventing and treating low blood levels of folic acid (folic acid deficiency), as well as its complications, including “tired blood” (anemia) and the inability of the bowel to absorb nutrients properly. Folic acid is also used for other conditions commonly associated with folic acid deficiency, including ulcerative colitis, liver disease, alcoholism, and kidney dialysis.

Women who are pregnant or might become pregnant take folic acid to prevent miscarriage and “neural tube defects,” birth defects such as spina bifida that occur when the fetus’s spine and back don’t close during development.

Some people use folic acid to prevent colon cancer or cervical cancer. It is also used to prevent heart disease and stroke, as well as to reduce blood levels of a chemical called homocysteine. High homocysteine levels might be a risk for heart disease.

Folic acid is used for memory loss, Alzheimer’s disease, age-related hearing loss, preventing the eye disease age-related macular degeneration (AMD), reducing signs of aging, weak bones (osteoporosis), jumpy legs (restless leg syndrome), sleep problems, depression, nerve pain, muscle pain, AIDS, a skin disease called vitiligo, and an inherited disease called Fragile-X syndrome. It is also used for reducing harmful side effects of treatment with the medications lometrexol and methotrexate.

Some people apply folic acid directly to the gum for treating gum infections.

Folic acid is often used in combination with other B vitamins.

How effective is it?

Natural Medicines Comprehensive Database rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.

The effectiveness ratings for FOLIC ACID are as follows:

Effective for...

  • Treating and preventing folic acid deficiency.

Likely effective for...

  • Lowering homocysteine levels in people with kidney disease. About 85% of people with serious kidney disease have high levels of homocysteine. High levels of homocysteine have been linked to heart disease and stroke. Taking folic acid lowers homocysteine levels in people with serious kidney disease.
  • Lowering homocysteine levels (“hyperhomocysteinemia”) in people with high amounts of homocysteine in their blood. High levels of homocysteine have been linked to heart disease and stroke.
  • Reducing harmful effects of a medicine called methotrexate, which is sometimes used to treat rheumatoid arthritis and psoriasis. Taking folic acid seems to reduce nausea and vomiting, which are possible side effects of methotrexate treatment.
  • Decreasing the risk of certain birth defects (neural tube defects) when taken by pregnant women.

Possibly effective for...

  • Reducing the risk of getting colorectal cancer. Getting more folic acid from the diet and supplements seems to lower the chances of developing colon cancer, but does not seem to help people who already have colon cancer.
  • Reducing the risk of breast cancer. The benefit is greater when women get extra vitamin B12 and vitamin B6 in their diet in addition to folic acid.
  • Depression, when used with conventional antidepressant medicines. Limited research suggests that folic acid alone won’t help with depression.
  • Treating a skin disease called vitiligo.
  • Gum problems due to a drug called phenytoin when applied to the gums.
  • Treating gum disease during pregnancy, when used in mouthwash.
  • Reducing the risk of pancreatic cancer.
  • Macular degeneration. Some research shows that taking folic acid with other vitamins including vitamin B6 and vitamin B12 might help prevent getting the eye disease called age-related macular degeneration.

Possibly ineffective for...

  • Reducing the risk of heart attack, stroke, and other related conditions in people with coronary heart disease.
  • Reducing the possibility of another stroke.
  • Reducing harmful effects of a medicine called lometrexol.
  • Chronic fatigue syndrome.

Likely ineffective for...

  • Treating an inherited disease called Fragile-X syndrome.

Insufficient evidence to rate effectiveness for...

  • Preventing re-blockage of blood vessels after angioplasty, a procedure to open a closed blood vessel. Taking folic acid plus vitamin B6 and vitamin B12 might actually interfere with healing in cases where a device (stent) is inserted in the blood vessel to keep it open.
  • Alzheimer’s disease. Limited evidence suggests that elderly people who get more folic acid than the recommended dietary allowance (RDA) appear to have a lower risk of developing Alzheimer’s disease than people who get less folic acid.
  • Memory and thinking skills in older people. There is conflicting evidence about the role of folic acid in age-related decline in memory and thinking skills.
  • Preventing cervical cancer. There is some evidence that increasing folic acid intake from dietary and supplement sources, along with thiamine, riboflavin, and vitamin B12, might help to prevent cervical cancer.
  • Male infertility. Some research suggests that taking folic acid plus zinc sulfate daily can increase sperm count in men with low sperm counts.
  • Lung cancer. There does not appear to be a relationship between low levels of folic acid and lung cancer.
  • Restless leg syndrome. Taking folic acid seems to reduce symptoms. Researchers are studying whether folic acid deficiency causes restless leg syndrome.
  • Cancer due to a disease called ulcerative colitis. Taking folic acid might help to keep people with ulcerative colitis from getting cancer.
  • Liver disease.
  • Alcoholism.
  • Age-related hearing loss.
  • Sickle cell disease.
  • Weak bones (osteoporosis).
  • Other conditions.
More evidence is needed to rate folic acid for these uses.

How does it work?

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Folic acid is needed for the proper development of the human body. It is involved in producing the genetic material called DNA and in numerous other bodily functions.

Are there safety concerns?

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Folic acid is LIKELY SAFE for most people. Most adults do not experience any side effects when consuming the recommended amount each day, which is 400 mcg.

High doses of folic acid might cause abdominal cramps, diarrhea, rash, sleep disorders, irritability, confusion, nausea, stomach upset, behavior changes, skin reactions, seizures, gas, excitability, and other side effects.

There is some concern that taking too much folic acid for a long period of time might cause serious side effects. Some research suggests that taking folic acid in doses of 800-1200 mcg might increase the risk of heart attack in people who have heart problems. Other research suggests that taking these high doses might also increase the risk of cancer such as lung or prostate cancer.

Don't take more than 400 mcg per day unless directed by your healthcare provider.

Are there interactions with medications?

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Be cautious with this combination.

There is some concern that taking large amounts of folic acid with 5-fluorouracil might increase some side effects of 5-fluorouracil, especially stomach problems. Talk with your healthcare provider before taking folic acid.

Capecitabine (Xeloda)
There is some concern that taking large amounts of folic acid might increase the side effects of capecitabine, especially stomach problems like diarrhea and vomiting. Talk with your healthcare provider before taking folic acid.

Fosphenytoin (Cerebyx)
Fosphenytoin (Cerebyx) is used for seizures. The body breaks down fosphenytoin (Cerebyx) to get rid of it. Folic acid can increase how quickly the body breaks down fosphenytoin (Cerebyx). Taking folic acid along with fosphenytoin (Cerebyx) might decrease the effectiveness of fosphenytoin (Cerebyx) for preventing seizures.

Methotrexate (MTX, Rheumatrex)
Methotrexate (MTX, Rheumatrex) works by decreasing the effects of folic acid in the body's cells. Taking folic acid pills along with methotrexate might decrease the effectiveness of methotrexate (MTX, Rheumatrex).

Phenobarbital (Luminal)
Phenobarbital (Luminal) is used for seizures. Taking folic acid can decrease how well phenobarbital (Luminal) works for preventing seizures.

Phenytoin (Dilantin)
The body breaks down phenytoin (Dilantin) to get rid of it. Folic acid might increase how quickly the body breaks down phenytoin (Dilantin). Taking folic acid and taking phenytoin (Dilantin) might decrease the effectiveness of phenytoin (Dilantin) and increase the possibility of seizures.

Primidone (Mysoline)
Primidone (Mysoline) is used for seizures. Folic acid might cause seizures in some people. Taking folic acid along with primidone (Mysoline) might decrease how well primidone works for preventing seizures.

Pyrimethamine (Daraprim)
Pyrimethamine (Daraprim) is used to treat parasite infections. Folic acid might decrease the effectiveness of pyrimethamine (Daraprim) for treating parasite infections.

Are there interactions with herbs and supplements?

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Green tea
There is some concern that green tea might keep folic acid from working the way it should in the body. This might lead to a condition that is similar to folic acid deficiency.

Are there interactions with foods?

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Taking folic acid with food reduces its absorption slightly, but probably not enough to be important.

Researchers don't agree on whether or not folic acid interferes with zinc absorption. But for people who get enough zinc in their diet, the effect of folic acid probably isn't important.

What dose is used?

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The following doses have been studied in scientific research:

  • For folic acid deficiency: the typical dose is 250-1000 mcg (micrograms) per day.
  • For preventing neural tube defects: at least 400 mcg of folic acid per day from supplements or fortified food should be taken by women capable of becoming pregnant and continued through the first month of pregnancy. Women with a history of previous pregnancy complicated by such neural tube defects usually take 4 mg per day beginning one month before and continuing for three months after conception.
  • For reducing colon cancer risk: 400 mcg per day.
  • For treating high levels of homocysteine in the blood:
    • 0.5-5 mg (milligrams)/day has been used, although 0.8-1 mg/day is appears to be more effective.
    • In people with end-stage renal disease, high homocysteine levels may be more difficult to treat, and doses of 0.8-15 mg/day have been used. Other dosage plans such as 2.5-5 mg 3 times weekly have also been used. Doses higher than 15 mg daily do not seem to be more effective.
  • For improving the response to medications for depression: 200-500 mcg daily has been used.
  • For vitiligo: 5 mg is typically taken twice daily.
  • For reduction of toxicity associated with methotrexate therapy for rheumatoid arthritis (RA) or psoriasis: 1 mg/day is probably enough, but up to 5 mg/day may be used.
  • For preventing macular degeneration: folic acid 2.5 mg, vitamin B12 (cyanocobalamin) 1000 mcg, and vitamin B6 (pyridoxine) 50 mg daily.
The adequate intakes (AI) for infants are 65 mcg for infants 0-6 months and 80 mcg for infants 7-12 months of age. The recommended dietary allowances (RDAs) for folate in DFE, including both food folate and folic acid from fortified foods and supplements are: Children 1-3 years, 150 mcg; Children 4-8 years, 200 mcg; Children 9-13 years, 300 mcg; Adults over 13 years, 400 mcg; Pregnant women 600 mcg; and breast-feeding women, 500 mcg. The tolerable upper intake levels (UL) of folate are 300 mcg for children 1-3 years of age, 400 mcg for children 4-8 years, 600 mcg for children 9-13 years, 800 mcg for adolescents 14-18 years, and 1000 mcg for everyone over 18 years of age.

Other names

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5'-methyltetrahydrofolate, 5'-MTHF, Acide Folique, Acide Ptéroylglutamique, Acide Ptéroylmonoglutamique, Acido Folico, B Complex Vitamin, Complexe de Vitamines B, Complexe Vitaminique B, Dihydrofolate, Folacin, Folacine, Folate, Folinic Acid, L-methylfolate, Methylfolate, Méthylfolate, Pteroylglutamic Acid, Pteroylmonoglutamic Acid, Pteroylpolyglutamate, Tetrahydrofolate, Tétrahydrofolate, Vitamin B9, Vitamine B9.


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To learn more about how this article was written, please see the Natural Medicines Comprehensive Database methodology.methodology (


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