Folic acid is a B vitamin that helps make new cells, normal red blood cells, and prevents anemia, birth defects, heart disease, stroke, and some cancers. Taking a daily multivitamin with 400 mcg of synthetic folic acid can reduce the risk of neural tube defects like spina bifida by up to 60%, anencephaly by 30%, and encephalocele by 10%, as these defects occur in 1 in 2,000 births and are a common cause of infant mortality.