Folic acid supports the earliest stages of human development.

Folic acid (vitamin B9) is essential for early cell and fetal development and deficiency is linked to neural tube defects; fortification and supplementation programs have reduced those risks.

Folic acid, also known as vitamin B9, is a B‑vitamin involved in early cell growth and fetal development. It was identified from yeast in the 1930s and later isolated from leafy greens such as spinach, which inspired its name. The vitamin was chemically defined and produced synthetically in the mid‑1940s and is available in supplements and fortified foods. Deficiency during early pregnancy has been linked to neural tube defects, including spina bifida and anencephaly. Key facts: - Folic acid and naturally occurring folates support DNA synthesis, cell growth and repair, red blood cell production, and nervous system development. - Neural tube defects form in the first months of gestation; research in the early 1980s found a strong association with folate deficiency and later studies reported that supplementation before and during pregnancy reduced spina bifida risk by about 72%. - In the late 1980s, health authorities in the U.S. and Canada broadly recommended supplementation for people planning pregnancy, and more than 80 countries now have mandatory folic acid fortification of grains and cereals. - Natural dietary folates occur in dark green leafy vegetables (for example, spinach), legumes, nuts and seeds, some meats, and in fortified grains and cereals. - The adult recommended dietary allowance cited is 400 micrograms per day, with 600 micrograms per day noted for pregnant and nursing people; an upper supplemental limit of 1,000 micrograms per day is commonly referenced. - About one third of the North American population is reported to have a genetic variation that reduces conversion of inactive folates to the active form (methyl tetrahydrofolate), which affects folate‑dependent methylation processes. Summary: Folic acid plays a central role in early development and in biochemical methylation pathways, and public health measures such as supplementation recommendations and food fortification have been associated with reduced rates of neural tube defects. Population differences in folate metabolism and ongoing monitoring of folate status are noted. Undetermined at this time.