Folic acid is a synthetic form of vitamin B9 used primarily to prevent birth defects, treat a specific type of anemia, and support cell growth throughout the body. It’s added to fortified foods like bread and cereal, sold as a supplement, and prescribed at higher doses during pregnancy. Your body needs it to build DNA and produce new cells, which makes it essential during any period of rapid growth.
Preventing Neural Tube Defects in Pregnancy
The most well-known use of folic acid is preventing neural tube defects, which are serious birth defects of the brain and spine that develop in the first few weeks of pregnancy, often before a person even knows they’re pregnant. The CDC recommends that all women capable of becoming pregnant get 400 micrograms (mcg) of folic acid daily, ideally starting at least one month before conception and continuing through early pregnancy.
This recommendation has driven a global public health effort. As of 2023, 69 countries have mandatory folic acid fortification programs, typically adding it to flour or grain products. Countries with these programs have seen population folate levels rise 50 to 100 percent and neural tube defect rates drop by 25 to 50 percent compared to countries without fortification. In the United States, enriched grain products have been fortified with folic acid since 1998.
Treating Folate-Deficiency Anemia
When your body doesn’t get enough folate, it can’t produce red blood cells properly. Instead of making normal-sized cells, your bone marrow produces oversized, immature red blood cells that don’t carry oxygen efficiently. This condition, called megaloblastic anemia, causes fatigue, weakness, shortness of breath, and pale skin.
Folate deficiency can develop from poor diet, heavy alcohol use, certain digestive conditions that impair absorption, or increased demand during pregnancy. Folic acid supplements or higher-dose prescriptions can correct the deficiency and restore normal blood cell production, typically within a few weeks. However, because vitamin B12 deficiency causes the same type of anemia, it’s important to identify which vitamin is actually low before starting treatment, since taking folic acid alone can mask a B12 problem.
Lowering Stroke Risk
Folic acid helps your body break down an amino acid called homocysteine. When homocysteine builds up in the blood, it’s associated with a higher risk of cardiovascular disease. Supplementation consistently lowers homocysteine levels, and a large meta-analysis of 23 randomized controlled trials found that folic acid reduced stroke risk by 10 percent overall. The benefit was dose-dependent: people whose homocysteine dropped by 5 or more units saw an 18 percent reduction in cardiovascular disease risk.
The effect on heart attacks specifically is less clear. The same analysis found no significant reduction in coronary heart disease risk from folic acid supplementation. So while folic acid appears to offer meaningful protection against stroke, it’s not a broad-spectrum heart disease treatment.
Supporting Cell Growth and DNA Production
At the cellular level, your body uses folate to build and repair DNA and to produce new cells. This makes it critical during periods of rapid cell division: pregnancy, infancy, adolescence, and recovery from illness or injury. It also plays a role in producing red and white blood cells in the bone marrow. Any tissue that turns over quickly, including the lining of your gut and your blood cells, depends on a steady supply of folate.
Cognitive Health in Older Adults
Low folate blood levels are associated with poorer cognitive performance in older adults, and correcting a deficiency may improve function. However, folic acid supplements don’t appear to help people who already have normal folate levels. Reviews of randomized controlled trials have shown mixed results on whether supplementation benefits healthy adults or those with mild to moderate cognitive decline. If you’re concerned about cognitive health, checking your folate level is a reasonable starting point, but folic acid is not an established treatment for dementia or Alzheimer’s disease.
Folic Acid vs. Natural Folate
Folic acid is the synthetic version of folate, a B vitamin found naturally in foods. The distinction matters because your body absorbs them at very different rates. Folic acid taken as a supplement on an empty stomach is essentially 100 percent bioavailable. The same amount in fortified food is about 85 percent bioavailable. Natural food folate, by comparison, is significantly less absorbable.
To account for this, nutrition labels use “dietary folate equivalents” (DFEs). One microgram of food folate counts as 1 DFE, while one microgram of folic acid taken with food counts as 1.7 DFE, and one microgram from a supplement taken on an empty stomach counts as 2 DFE. This means you’d need roughly twice as much folate from food to match what you’d get from a supplement.
Best Food Sources of Folate
While supplements and fortified foods are the most efficient way to get folic acid, natural folate is abundant in certain foods. The richest sources per serving:
- Beef liver (3 ounces, braised): 215 mcg
- Spinach (½ cup, boiled): 131 mcg
- Black-eyed peas (½ cup, boiled): 105 mcg
- Asparagus (4 spears, boiled): 89 mcg
- Brussels sprouts (½ cup, frozen and boiled): 78 mcg
- Romaine lettuce (1 cup, shredded): 64 mcg
- Avocado (½ cup, sliced): 59 mcg
- Broccoli (½ cup, frozen and cooked): 52 mcg
Most adults need 400 mcg DFE per day. Pregnant women need 600 mcg DFE. Getting there from food alone is possible but requires consistent effort, especially with leafy greens and legumes at most meals. That’s part of why fortification and supplements remain the primary strategy for populations at risk of deficiency.