Folic acid (synthetic)

Tier 2 — promising · Pregnancy · Neural tube defects · Prenatal · MTHFR consideration

The synthetic form of vitamin B9 used in food fortification worldwide and in most prenatal vitamins. Periconceptional supplementation at 400-800 mcg/day reduces neural tube defect risk by approximately 50-70%, one of the most replicated findings in nutritional epidemiology. Critical limitation: up to 40% of people carry MTHFR C677T variants reducing conversion of folic acid to active 5-MTHF by 30-70%, meaning some individuals benefit less from this synthetic form. High-dose folic acid above 1,000 mcg/day (the NIH tolerable upper limit) can mask vitamin B12 deficiency by correcting…

Dose: Standard supplementation: 400 mcg/day. Periconceptional (pregnancy planning and first trimester): 400-800 mcg/day. Previous NTD pregnancy or high-risk: 5 mg/day (prescription). Do not exceed 1,000 mcg/day supplemental without medical supervision.