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Not medical advice. The Atlas is not a substitute for a clinician who can examine you.

Folate / Folic Acid

Vitamin B9 · The Neural-Tube Nutrient

Evidence grade 5 of 5, Settled. Read how the Atlas grades evidence.

3 human trials, about 12 studies, Population-level (national fortification data). The written rationale for this grade is still being prepared.

FDA
Folic acid food fortification mandated by FDA since 1998
WADA
Not prohibited

Reference only. Not medical advice.

What can go wrong

Folic acid is water-soluble and routine excess is generally excreted, but high intake can mask the blood signs of vitamin B12 deficiency, which matters especially for people who are vegan or older. The high-dose regimen used for those at elevated risk is a medical decision made with a provider, not a default. Folic acid does not prevent every neural tube defect even with full adherence, and its effect can be reduced in poorly controlled diabetes, in obesity, and alongside certain antiseizure medicines. Amounts and timing, and whether a higher dose applies, should be decided with an obstetric provider or midwife rather than self-selected.

Folate is vitamin B9, needed for cell division and for closure of the neural tube, the structure that becomes the brain and spinal cord and finishes forming within about the first 28 days after conception, often before a person knows they are pregnant. That early timing is why every major health body recommends starting a supplement before conception rather than after a positive test. Folic acid is the synthetic form in supplements and fortified grain; food folate is the form in leafy greens, beans, lentils, and citrus. The prevention evidence is unusually settled, resting on two landmark randomized trials, a large field trial in China, a Cochrane meta-analysis, and decades of population data after countries began fortifying flour. Amounts here are the guidelines' own figures, and decisions about them belong with an obstetric provider or midwife.

The single strongest case in prenatal nutrition: starting before conception cuts the risk of neural tube defects by roughly half.

What people take it for

What it is taken for. Approval, where it exists, covers only some of these.

  • Preventing neural tube defects such as spina bifida and anencephaly
  • Supporting fetal cell division and growth during early development
  • Reducing risk of some other folate-sensitive birth defects
  • Maintaining maternal folate stores through pregnancy and lactation
  • Supporting healthy red blood cell formation and preventing folate-deficiency anemia

What people get wrong

  • Often saidIf I eat well I do not need a folic acid supplement.

    ActuallyEven where grain is fortified, roughly a third of pregnant people in the US have folate intake below the estimated average requirement, per the NIH Office of Dietary Supplements. Because the neural tube closes so early, USPSTF and WHO recommend a supplement for anyone who could become pregnant, not only those actively trying.

  • Often saidIf I have an MTHFR gene variant I must take methylfolate instead of folic acid.

    ActuallyCDC states plainly that this is not true: people with an MTHFR variant can process all forms of folate, including folic acid, and 400 mcg of folic acid still helps prevent neural tube defects. CDC notes folic acid intake matters more than MTHFR status for blood folate. ACMG and ACOG advise against routine MTHFR testing in this setting.

  • Often saidYou can wait until you learn you are pregnant to start.

    ActuallyThe neural tube finishes closing within about the first 28 days, frequently before a positive test, so guidelines set supplementation to begin before conception. WHO frames it as starting from the moment a person begins trying to conceive.

  • Often saidEveryone should take the 4 mg high dose to be safe.

    ActuallyThe 4 mg figure comes from the MRC recurrence trial and is a guideline amount for people with a prior affected pregnancy or specific high-risk factors. USPSTF's Grade A recommendation of 0.4 to 0.8 mg does not apply to that high-risk group, whose regimen is set individually with a clinician.

Who profits, and who pushes back

  • CDC, ACOG, USPSTF & AAP

    championsMajor US health authorities

    There is high certainty that folic acid supplementation has a substantial net benefit for persons who could become pregnant. All four bodies recommend 400-800 mcg daily, reaffirmed through 2023-2025.

  • American Academy of Pediatrics

    championsPediatric policy (reaffirmed March 2025)

    Periconceptional folic acid can prevent 50% or more of neural tube defects, yet fewer than one in three women consume the recommended amount; closing that gap is the priority.

  • Lily Nichols, RDN

    Sells this. Has a commercial interest in a product sold as this compound, as of July 2026.

    caveatsDietitian, author of Real Food for Pregnancy

    Argues food folate plus a prenatal with methylfolate is preferable to synthetic folic acid, citing MTHFR variants in an estimated 40-60% of people. A widely read author with book and content interests; her dose target (600-800 mcg) matches the guidelines even as she favors a different form.

  • Dr. Ben Lynch

    Sells this. Has a commercial interest in a product sold as this compound, as of July 2026.

    cautionsNaturopath, author of Dirty Genes; founder, Seeking Health

    The leading popularizer of avoiding folic acid in favor of methylfolate for people with MTHFR variants. Carries a direct commercial interest as founder of a methylfolate supplement company; the "avoid all folic acid" position goes beyond what guideline bodies support.

  • Folic-acid fortification scientists

    endorsesPublic-health and metabolism researchers

    A randomized trial of methylfolate versus folic acid would be unethical, since it would require withholding folic acid from some pregnancies; the prevention evidence rests on folic acid, so it remains the recommended form.

Where the research comes from

Most of the published research on this comes from one place. 60% of it is from Fortified countries. Findings that no unrelated group has reproduced are weaker than the study count makes them look.

Share of published research by country of origin.
PlaceShare of published research
Fortified countries60%
Non-fortified40%

Research published from: Global.

How we got here

Folate was isolated in the 1940s from spinach, which gave it its name from the Latin for leaf, and from liver extracts studied for anemia in pregnancy, work advanced in India by Lucy Wills, who in the 1930s traced a form of pregnancy anemia among mill workers in Bombay to a dietary factor later identified as folate. The neural tube connection came later. Richard Smithells in Britain reported in the 1980s that vitamin supplements seemed to lower recurrence, an observation strong enough to prompt a definitive trial. The UK Medical Research Council Vitamin Study, run across seven countries and published in 1991, settled the recurrence question with a randomized design. Andrew Czeizel and Istvan Dudas in Hungary then answered first occurrence in 1992. A China-US collaboration led by Robert Berry and Zhu Li confirmed the effect at population scale by 1999. Policy followed fast: the United States mandated folic acid in enriched grain from 1998, and many countries adopted fortification afterward.

  1. 1931Lucy Wills links a pregnancy anemia in Bombay mill workers to a dietary factor, later identified as folate
  2. 1941The compound is isolated from spinach and named folate, from the Latin for leaf
  3. 1980sRichard Smithells reports that periconceptional vitamins appear to lower neural tube defect recurrence, prompting a formal trial
  4. 1991MRC Vitamin Study (Lancet) randomized trial finds 4 mg folic acid gives a 72% protective effect against recurrence (RR 0.28); stopped early
  5. 1992Czeizel and Dudas (NEJM) randomized trial shows a supplement with folic acid prevents first-occurrence defects; US Public Health Service recommends 400 mcg for those who could become pregnant
  6. 1998FDA folic acid fortification of enriched grain becomes mandatory in the US at 140 mcg per 100 g
  7. 1999Berry and Li (NEJM) China-US field project confirms 400 mcg cuts risk by up to 85% in a high-prevalence region
  8. 2015Cochrane review (De-Regil) pools trials to a risk ratio of 0.28 (95% CI 0.15 to 0.52)
  9. 2023USPSTF reaffirms its Grade A recommendation for 0.4 to 0.8 mg daily after an updated evidence review

At a glance

Standard dose
400-800 mcg/day
High-risk dose
4,000 mcg/day
Pregnancy RDA
600 mcg DFE
USPSTF grade
A

What this entry does not yet cover

What follows is unfinished work on our side, not a finding about Folate / Folic Acid. A short entry is not a safe entry.

  • Cost and market. We have not documented what it sells for or who sells it.
  • Supply chain. We have not mapped where it is made.
  • Who uses it. We have not documented the user groups.
  • What could change. No forward-looking summary yet.
  • How it compares. We have not set it against the alternatives.
  • Children and teenagers. We have not checked what is known about younger people.

Sources