Folic acid, also known as vitamin B9, is a water-soluble vitamin that plays several important roles in the body. It is required for cell growth and DNA synthesis, and is especially important during periods of rapid cell division and growth like infancy and pregnancy. A deficiency in folic acid can lead to megaloblastic anemia and neural tube defects in newborns if a woman is deficient during pregnancy. Good dietary sources include leafy green vegetables, beans, oranges, and fortified grains.