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Folic acid (synthetic)

Pregnancy · Neural tube defects · Prenatal · MTHFR consideration

Tier 2 — Promising

What it is

The synthetic form of vitamin B9 used in food fortification and most prenatal vitamins. Gold standard evidence for neural tube defect prevention: 400–800 mcg/day starting 1 month before conception reduces NTD risk by 70% (one of the most replicated findings in nutrition). Critical limitation: up to 40% of people carry MTHFR C677T variants that reduce conversion of folic acid to active methylfolate (5-MTHF) by 30–70%. For these individuals, 5-MTHF directly bypasses the conversion bottleneck. High-dose folic acid (>1,000 mcg/day) can mask vitamin B12 deficiency by correcting megaloblastic anaemia while neurological damage continues silently.

Efficacy

4/5

Safety

3/5

Research

5/5

Onset

3/5

Cost

5/5

Drug-int.

3/5

Dose

400 mcg/day standard supplementation. 400–800 mcg/day for pregnancy planning and first trimester. 5 mg/day (prescription) for previous NTD or high risk.

Time of day & tips

All women of childbearing age should supplement folate. If MTHFR status is unknown, 5-MTHF (methylfolate) is the safer universal choice. High-dose folic acid above 1,000 mcg/day can mask B12 deficiency — always monitor B12 alongside. Most prenatal vitamins contain 400–800 mcg.

Cycling

Safe for continuous daily use indefinitely. Essential throughout pregnancy and breastfeeding. No cycling needed.

Sensitive populations: This supplement's evidence base touches pregnancy, pediatric, or other sensitive populations. Confirm any change with your healthcare provider before use.

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