Folic acid is a synthetic form of the essential B vitamin folate and is widely available as a dietary supplement and in fortified foods. Folic acid is the most widely available form of supplemental folate due to its high stability and bioavailability. Folate, or vitamin B9, is required for many vital biological pathways, including DNA synthesis, repair, and methylation; neurotransmitter synthesis; and the metabolism of homocysteine and other amino acids.[1][2] Accordingly, a folate deficiency may increase the risk of various diseases and can negatively affect fetal development during pregnancy.
The human body can’t make folate (apart from small amounts produced by the intestinal microbiome), so folate must be consumed in the diet or through supplementation.[3] Folate occurs naturally in a variety of foods, including green leafy vegetables, legumes, citrus fruit, eggs, and liver.[4] Additionally, some countries have mandated the fortification of certain cereal grains with folic acid (e.g., wheat, corn, rice), resulting in widespread exposure to folic acid through foods like bread and cereal.
While folic acid can serve a therapeutic role in certain contexts, supplementation in excess may have risks.