Folic acid, or vitamin B9 (also called folate or folacin), is needed for energy production and a strong immune system. Folate is necessary for the production and maintenance of new cells. This is especially important during periods of rapid cell division and growth such as infancy and pregnancy.

Folic Acid is needed to replicate DNA. It also helps prevent changes to DNA that may lead to cancer. Thus folate deficiency hinders DNA synthesis and cell division, affecting most clinically the bone marrow, a site of rapid cell turnover. Because RNA and protein synthesis are not hindered, large red blood cells called megaloblasts are produced, resulting in megaloblastic anemia. Both adults and children need folate to make normal red blood cells and prevent anemia.

Leaf vegetables such as spinach and turnip greens, dried beans and peas, fortified cereal products, and some other fruits and vegetables are rich sources of folate. Some breakfast cereals (ready-to-eat and others) are fortified with 25 percent or 100 percent of the recommended dietary allowance (RDA) for folic acid: however, many of them also contain 'undesirable' nutrients such as sugar.