Q: First we were told that folic acid supplementation was good, but now we’re hearing that it’s bad. What’s the debate? A: Folic acid is the synthetic form of the naturally occurring B vitamin folate. It is added to certain foods because, when taken before and during pregnancy, it reduces the risk of having a baby with a neural tube defect (such as spina bifida) by as much as 50%. However, folic acid supplementation also has other effects — some positive, some negative. For instance, folic acid…
  • May help prevent cognitive decline in people with adequate levels of vitamin B-12. But: For people deficient in B-12, folic acid may accelerate cognitive decline.
  • Lowers levels of homocysteine (an amino acid that damages artery linings) and so theoretically it may protect against coronary artery disease and stroke. However, clinical trials have shown no such benefits from folic acid supplementation.
  • May protect against DNA damage that can lead to cancer. But: Folic acid may promote the growth of some existing cancers or precancerous growths (such as colon polyps) and interfere with cancer medications.
  • Bottom line: The body needs folate to produce and maintain cells. A healthful intake is about 400 micrograms (mcg) per day. You can get all you need — but are highly unlikely to get too much — from diet alone, whether from foods that contain folate naturally (dark leafy greens, legumes, oranges, peanuts) or from foods fortified with folic acid (bread, cereal, rice).

    Due to the aforementioned risks, taking additional supplements of folic acid is generally not a good idea. However, there are exceptions. It is hard to find a multivitamin that does not contain folic acid — so if you want to take a daily multivitamin, be sure to choose one with no more than 400 mcg of folic acid. If you are pregnant or might get pregnant, ask your doctor about supplementing with 400 mcg to 1,000 mcg of folic acid per day… or with a higher dosage if you or a close relative previously had a baby with a neural tube defect. Your doctor may recommend supplementation if you have a diagnosed folate deficiency or type of anemia caused by low folate… have celiac disease or inflammatory bowel disease, as these conditions impair folate absorption… have high homocysteine levels… or take methotrexate (Trexall) for psoriasis or rheumatoid arthritis, because this drug depletes folate levels.