- Folic acid, also known as vitamin B9, is a water-soluble B-complex vitamin that plays a fundamental role in DNA synthesis, cell division, amino acid metabolism, and the formation of red and white blood cells.
- In its natural form, it is known as folate, which occurs in foods, while folic acid is the synthetic form used in supplements and food fortification. Once consumed, folic acid is converted in the liver and other tissues into its biologically active form, tetrahydrofolate (THF), which acts as a coenzyme in several vital biochemical reactions, particularly those involving the transfer of single-carbon units.
- Folate is essential for supporting rapid cell growth and division, making it especially important during periods of high metabolic demand, such as pregnancy, infancy, and adolescence. One of its most well-known roles is in preventing neural tube defects (NTDs), such as spina bifida and anencephaly, which can occur early in pregnancy. For this reason, women of childbearing age are advised to consume adequate folic acid daily—even before becoming pregnant—as neural tube development occurs within the first few weeks of gestation, often before a pregnancy is confirmed.
- Dietary sources of natural folate include leafy green vegetables (such as spinach and kale), legumes, citrus fruits, eggs, liver, and whole grains. Folic acid, the synthetic form, is commonly added to fortified foods like cereals, bread, pasta, and flour to help reduce the risk of deficiency in the general population. Because folate is water-soluble and sensitive to heat and light, cooking methods such as boiling can significantly reduce its availability in food.
- Folate deficiency can occur due to inadequate dietary intake, malabsorption syndromes (such as celiac disease), chronic alcoholism, or increased requirements during pregnancy. Certain medications, including methotrexate, phenytoin, and sulfasalazine, can also interfere with folate metabolism. Deficiency symptoms include megaloblastic anemia (characterized by large, immature red blood cells), fatigue, weakness, irritability, mouth sores, and cognitive issues such as forgetfulness or confusion. In pregnant women, folate deficiency significantly increases the risk of fetal developmental abnormalities.
- While folic acid supplementation is generally safe and well tolerated, excessive intake—especially from supplements—can mask the symptoms of vitamin B12 deficiency, particularly the hematologic effects, while allowing irreversible neurological damage to progress undetected. For this reason, upper intake levels have been established for synthetic folic acid (1,000 mcg/day for adults), though no limit exists for naturally occurring folate from food sources.
