Known in supplement form as “folic acid,” folate promotes healthy cell growth; aids in the form-ation of genetic material in cells; prevents changes to DNA that may lead to cancer; and regulates homocysteine levels.

How Much: Recommended dietary allowance (RDA) = 400 micrograms (mcg) for adults; 600 mcg for pregnant women. 

Too Much: More than 1,000 mcg of supplemental folic acid per day may mask a vitamin B-12 deficiency, leading to anemia, especially in older adults. If you’re older than 50, have your B12 levels checked before taking folic acid supplements.

Too Little: A folate deficiency can cause fatigue, mouth ulcers, swollen tongue, weight loss and poor growth. It can also cause an increased risk for certain cancers, anemia, depression, heart disease and Alzheimer's disease. Low levels in pregnant women increase the risk of neural tube defects in their babies. 

Foods: Folate is found in green leafy vegetables such as spinach and kale; orange juice and most fruits; dried beans and peas; and enriched grains, cereals and pastas.

Interactions: Antiseizure medications; ulcerative colitis medications; methotrexate (often used to treat cancer and autoimmune conditions); antacids; alcohol, antibiotics; aspirin; some cholesterol-lowering drugs; oral contraceptives; cholesterol-lowering medications. 

Research Note: Folic acid counteracts side effects of methotrexate, such as nausea, mouth ulcers and liver inflammation, and is almost always prescribed for people taking the drug. Doses range from 1,000 to 5,000 mcg daily; sometimes a single weekly dose is taken the morning after a methotrexate injection. Recent studies also suggest folic acid supplements may protect against a first stroke.