Folic acid helps with fetal development and may even keep your heart healthy. The natural form of folic acid, folate, occurs in foods such as leafy vegetables. It's water-soluble, so the body simply removes any excess folate from the body in urine. As a supplement, folic acid may cause some problems in higher doses, particularly when it comes to drug interactions.
Drug Interactions
Folic acid may interact with other drugs. Some drugs affect your body's ability to use folic acid, which may mean you lose out on the health benefits. For example, cholesterol-lowering medication such as colestipol and cholestyramine may prevent effective absorption of folic acid. Other medication for conditions such as high blood pressure, infection or seizures can reduce folic acid absorption. Even large doses of aspirin may interfere with folic acid supplements. Folic acid may affect the efficacy of some antibiotics such as tetracycline.
Methotrexate
The drug methotrexate, used to treat some cancers, rheumatoid arthritis and other auto-immune conditions lowers your body's folic acid levels. Most doctors will prescribe higher doses of folic acid to counter this effect. However, if you're taking methotrexate to treat cancer, you may have to avoid folic acid supplements as these may stop the drug from working effectively.
B12
Taking more than 1,000 mcg of folic acid from supplements per day can mask symptoms of B12 deficiency. In general, B12 deficiency tends to occur in people older than 50, or in people suffering from digestive conditions such as Crohn's disease. Strict vegans who eat no animals products may also be at risk of a B12 deficiency. You body needs B12 for proper brain and nervous system function. A lack of B12 masked by folic acid might lead to nerve damage in the body.
Doses
Though you're unlikely to get any serious side effects from too much folic acid, the Institute of Medicine recommends different upper daily doses for certain age groups and conditions. For example, babies and toddlers should take no more than 300 mcg per day. Children between 4 and 8 can take 400 mcg per day. Older children up to 13 should take no more than 600 mcg, while teenagers should have no more than 800 mcg. Adults, including pregnant women, can take up to 1,000 mcg. These are the upper limits and not necessarily the suggested dose.
References
- University of Maryland Medical Center; Vitamin B9 (Folic Acid); Steven D. Ehrlich, N.M.D.; May 18, 2009
- Womenshealth.gov; Can Women Get Too Much Folic Acid?; May 18, 2010
- Office of Dietary Supplements: Dietary Supplement Fact Sheet: Folate
- Linus Pauling Institute; Folic Acid; Jane Higdon, Ph.D.; April 2002
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