Vitamin B9 (Folate / Folic Acid)

What Is Vitamin B9 (Folate / Folic Acid)?

Vitamin B9 encompasses a family of related compounds collectively called folates. In food, folate occurs in reduced, polyglutamate forms. The synthetic form used in supplements and fortified foods is folic acid, which is more stable and more bioavailable (approximately 85% from fortified food vs. roughly 50% of food folate on average). Dietary Folate Equivalents (DFEs) account for this difference.

The RDA for adults is 400 mcg DFE/day. During pregnancy the requirement rises to 600 mcg DFE/day, with supplemental folic acid specifically recommended because timing of neural tube closure (days 21-28 post-conception) often precedes confirmed pregnancy.

Key Functions

• DNA synthesis and repair: Tetrahydrofolate (THF) derivatives donate one-carbon units required for purine and thymidine synthesis, making folate essential for cell division.
• Amino acid interconversion: Folate participates in the conversion of homocysteine to methionine (in concert with vitamin B12) and serine to glycine.
• Red blood cell maturation: Deficiency impairs DNA replication in rapidly dividing erythrocyte precursors, leading to megaloblastic anemia with large, immature red cells.
• Neural tube development: Adequate periconceptional folate reduces the risk of neural tube defects (spina bifida, anencephaly) by approximately 70%.

Food Sources

Naturally rich sources include dark leafy greens (spinach, romaine, asparagus), legumes (lentils, black-eyed peas, chickpeas), beef liver, avocado, and broccoli. In many countries, wheat flour and corn masa are mandatorily fortified with folic acid. Folate in food is heat-labile; prolonged boiling can reduce content by 50% or more.