Overview

Vitamin B9 includes food folates and folic acid. Folate coenzymes transfer one-carbon units for DNA synthesis, amino-acid metabolism, and methylation. See Vitamin B9, Vitamin B12, and B-complex vitamins.

Mechanism

Tetrahydrofolate derivatives support thymidylate and purine synthesis and work with vitamin B12 in methionine regeneration. Folate demand rises during periods of rapid cell division.

Uses

Folic acid prevents neural-tube defects and treats folate deficiency. It is used in pregnancy planning, megaloblastic anemia caused by deficiency, and some antifolate-related protocols under medical supervision.

Dosage

Adults commonly require about 400 micrograms dietary folate equivalents daily; pregnancy increases this to about 600 micrograms. People who could become pregnant are commonly advised to obtain 400 micrograms folic acid daily, while higher doses require clinician direction.

Adverse effects

Folic acid is generally tolerated. High supplemental intake can mask vitamin B12 deficiency while neurologic injury progresses, so unexplained anemia or neurologic symptoms require evaluation.

Claims and evidence

Periconceptional folic acid reduces neural-tube-defect risk. Evidence for preventing unrelated chronic diseases through high-dose supplementation is inconsistent.

Research

Research examines methylation, pregnancy outcomes, cancer biology, pharmacogenomics, and folate–B12 interactions.