Folate
Folic acid · Vitamin B9 · Folacin · L-methylfolate · 5-MTHF · L-5-methyltetrahydrofolate · Metafolin · Quatrefolic · Pteroylglutamic acid · Vitamin B-9
The one prenatal nutrient with real trial data behind it — and the form that actually earned it.
Folate is vitamin B9; 400-800 mcg DFE of folic acid daily before and during early pregnancy is one of the best-proven interventions in medicine for preventing neural-tube defects.
Nature Made Folic Acid 400 mcg (665 mcg DFE)
What is Folate?
Folate is vitamin B9, an essential water-soluble vitamin your body cannot make. "Folate" refers to the natural forms found in leafy greens, legumes and liver, while "folic acid" is the synthetic, fully oxidized form used in supplements and food fortification. Supplements come in two camps: plain folic acid (cheap, shelf-stable, and the exact molecule tested in the trials that established neural-tube-defect prevention) and reduced "active" forms sold as L-methylfolate, 5-MTHF, Metafolin or Quatrefolic (marketed as needing no conversion). The honest headline: for the flagship prenatal use case, folic acid is the form with the outcome data. Methylfolate raises blood folate efficiently and is a reasonable choice for people with known MTHFR variants or who simply prefer it, but no methylfolate product has ever been shown in a trial to prevent a neural-tube defect. The clinical target for either form is 400-800 mcg DFE per day.
How it works
Folate is the carrier of one-carbon units your cells use to build and repair DNA and to make new red blood cells — demands that spike during the rapid tissue growth of early pregnancy. Adequate folate during the first four weeks after conception, when the neural tube closes into the brain and spinal cord, sharply lowers the risk of defects like spina bifida and anencephaly. Folate also converts homocysteine back to methionine; when folate is low, homocysteine accumulates. All dietary and supplemental folates must ultimately be reduced to L-5-methyltetrahydrofolate (5-MTHF), the form that circulates in blood and crosses into cells. Folic acid takes a couple of extra enzymatic steps to get there; methylfolate is already in that final form. The MTHFR enzyme runs one of those steps, and common gene variants (677C>T) modestly slow it — the biochemical hook the methylfolate marketing hangs on. In practice, at the low doses used for prevention, people with these variants still convert folic acid well enough to reach protective blood levels, which is why public-health bodies still recommend folic acid for everyone.
At-a-glance facts
- Best form for prevention
- Folic acid — the form with the trial data
- Standard daily dose
- 400-800 mcg DFE
- When to start
- At least 1 month before conception
- MTHFR variant
- Methylfolate optional, not required for most
- Tolerable upper limit
- 1,000 mcg/day synthetic folic acid (adults)
- Evidence base
- Randomized trials + Cochrane review
- Cost of proven form
- Often under $0.05/day
Evidence: Folic acid's prevention of neural-tube defects is backed by randomized controlled trials and a Cochrane review — rare, top-tier evidence — but that gold standard applies to folic acid, not to the newer methylfolate forms, whose benefit over folic acid is extrapolated from blood-level data rather than proven on outcomes.
Who it's for — and who it isn't
- Anyone who could become pregnant — every guideline recommends 400-800 mcg DFE daily starting at least a month before conception, because the neural tube closes before most people know they are pregnant
- People who are pregnant or planning pregnancy who want the single best-evidenced supplement for that stage of life
- People with elevated homocysteine or on medications that deplete folate (methotrexate, some anticonvulsants), where extra folate is genuinely indicated
- People with a known MTHFR variant who prefer methylfolate for peace of mind — a defensible choice even though folic acid also works
- Anyone eating a diet low in leafy greens, legumes and fortified grains who wants basic B9 insurance
- People with no reproductive plans and a folate-rich diet, who likely get enough from food and fortified grains without a dedicated pill
- Anyone buying premium methylfolate expecting it to out-prevent birth defects — that superiority claim has no trial data behind it
- People with untreated or undiagnosed B12 deficiency, where high-dose folic acid can mask the anemia while nerve damage progresses — sort out B12 first
- Anyone assuming a higher dose is better; past 800-1,000 mcg there is no added prevention benefit for the general population
Week-by-week, what happens
- The critical windowThe neural tube closes by about day 28 — often before a pregnancy is detected — so folate must already be on board; supplementation ideally begins 1 month before conception
- 1-2 weeksRed-blood-cell folate begins climbing and homocysteine starts to fall once daily intake is consistent
- 4-12 weeksRed-cell folate reaches a protective steady state and plateaus with continued daily dosing
- Throughout pregnancyContinued intake supports rapid maternal and fetal tissue growth and helps maintain healthy blood counts
Safety & contraindications
- High-dose folic acid can mask the anemia of vitamin B12 deficiency while nerve damage silently progresses — screen and correct B12 before taking large amounts, especially if over 50 or on a plant-based diet
- The tolerable upper intake level for synthetic folic acid is 1,000 mcg/day for adults; the 400-800 mcg prenatal range sits well under it, but stacking multiple fortified products can push you over
- "MTHFR requires methylfolate" is largely marketing — at prevention doses, people with common MTHFR variants still convert folic acid adequately, and no methylfolate product has trial evidence of preventing neural-tube defects
- Gummy and combination prenatal products add sugar, cost and label complexity; a plain folic acid tablet delivers the proven protection more cheaply
- Anyone on methotrexate, sulfasalazine or certain anticonvulsants, or with a history of NTD-affected pregnancy, should discuss dosing with a clinician, as needs can differ substantially from the standard 400 mcg
All articles on Folate
Best Folate Supplements
Why Getting Folate Right Matters — and Why the Form Debate Is Overblown
Read →Best Iron Supplements
Why Iron Supplements Matter — and Where the Hype Ends
Read →Best Multivitamin for Women
The 9 best multivitamins for women, cohort-ranked on nutrient forms (methylfolate over folic acid), the iron fork (menstruating vs post-menopausal — both addressed honestly), testing and value — gap-insurance framing, explicitly not prenatal advice.
Read →Best Omega-3 for Women
The same 10-product omega-3 roster re-scored for women — prenatal/preconception DHA (Coletta 2010), postpartum + perimenopausal mood (Freeman 2006), post-menopause heart, skin/hair/nails, swallowability, and a higher-ranked vegan algal pick.
Read →Centrum Women Multivitamin Review
The most complete drugstore women's formula — full iron, basic forms, no seal.
Read →Jarrow Formulas Methyl Folate 400 mcg Review
An affordable entry into active methylfolate at the standard 400 mcg dose — but the cheap active form still isn't the proven prenatal choice.
Read →MaryRuth's Organic Prenatal Gummies (Methylfolate 800 mcg DFE) Review
A palatable organic prenatal gummy at the 800 mcg DFE target — genuinely useful if you can't swallow pills, but a compromise on form, cost and sugar.
Read →Nature Made Folic Acid 400 mcg (665 mcg DFE) Review
The exact form and dose proven in randomized trials to cut neural-tube-defect risk, USP Verified, at pennies a day.
Read →Nordic Naturals Prenatal DHA Review
Prenatal DHA audit — DHA/EPA per serving, the rTG form, third-party testing, and an honest pregnancy verdict (it's not a full prenatal multi — talk to your OB).
Read →NOW Foods Folic Acid 800 mcg + B-12 Review
The proven folic acid form at a higher 800 mcg dose, paired with B-12, for the lowest cost on this list.
Read →NOW Foods Methyl Folate 1,000 mcg Review
High-dose 1 mg active folate at a value price — but it combines an above-target dose with a form that lacks NTD-prevention evidence.
Read →One A Day Women's Multivitamin Review
The cheap women-specific tablet — honest basics, every corner cost-engineered.
Read →Pure Encapsulations Folate 400 (Metafolin L-5-MTHF) Review
Hypoallergenic, third-party-tested L-methylfolate at the right dose — the cleanest methylfolate for sensitive users.
Read →SmartyPants Women's Multivitamin Gummies Review
The best-built women's gummy — buy it only if tablets are truly off the table.
Read →Solgar Folate 666 mcg DFE (Metafolin 400 mcg) Review
Bioidentical L-methylfolate at the right dose — the best-in-class choice if you have a confirmed MTHFR variant, but not the proven NTD form.
Read →Solgar Folic Acid 400 mcg Review
Clean, single-ingredient folic acid at the exact 400 mcg NTD-prevention dose from a trusted heritage brand.
Read →Thorne 5-MTHF 1 mg (Methylfolate) Review
Therapeutic-strength 1 mg active methylfolate from a top clinician brand — useful for elevated homocysteine, overkill for routine prenatal use.
Read →FAQ
Is folic acid or methylfolate better for pregnancy?
Folic acid, if you go by evidence. It is the exact form used in the randomized trials that proved neural-tube-defect prevention. Methylfolate raises blood folate efficiently and is a fine personal choice — especially with a known MTHFR variant — but no methylfolate supplement has ever been shown in a trial to prevent a birth defect. For most people, plain folic acid at 400-800 mcg DFE is the proven, inexpensive default.
I have an MTHFR gene variant — do I need methylfolate?
Probably not. Common MTHFR variants (like 677C>T) modestly slow one conversion step, but at the low doses used for prevention, affected people still reach protective blood folate levels on folic acid. Methylfolate is a reasonable option if you prefer it or have documented elevated homocysteine, but it isn't required, and folic acid remains the guideline recommendation for everyone.
How much folate should I take and when?
400-800 mcg DFE daily, starting at least one month before conception and continuing through early pregnancy. The neural tube closes by about day 28 — often before you know you're pregnant — which is why timing matters more than dose. Higher amounts don't add prevention benefit for the general population and can approach the 1,000 mcg synthetic upper limit.
What does DFE mean on the label?
DFE stands for Dietary Folate Equivalents, a standardized unit that accounts for the fact that synthetic folic acid is absorbed more efficiently than natural food folate. On supplement labels, 400 mcg of folic acid is listed as roughly 665 mcg DFE. It lets you compare folic acid and methylfolate products on the same scale — aim for 400-800 mcg DFE.
Can folic acid be harmful?
At prenatal doses it's very safe. The main caveat is that high folic acid can mask vitamin B12 deficiency, hiding the anemia while nerve damage continues — so B12 status matters, especially for older or plant-based eaters. Staying under the 1,000 mcg/day synthetic upper limit and not stacking multiple fortified products keeps you in the well-studied safe range.
Do I still need a folate supplement if I eat well and grains are fortified?
If you might become pregnant, yes — food and fortification make it hard to reliably hit the periconceptional target through diet alone, and the stakes in that window are high. Outside of reproductive plans and with a diet rich in leafy greens and legumes, a dedicated folate pill is often unnecessary.
Sources & further reading
- MRC Vitamin Study Research Group. Prevention of neural tube defects: results of the Medical Research Council Vitamin Study. Lancet. 1991;338(8760):131-137.Prevention of neural tube defects: results of the Medical Research Council Vitamin Study
Randomized trial showing 4 mg/day folic acid reduced recurrence of neural-tube defects by about 72% in high-risk women — the landmark proof for folic acid.
- Czeizel AE, Dudás I. Prevention of the first occurrence of neural-tube defects by periconceptional vitamin supplementation. N Engl J Med. 1992;327(26):1832-1835.Prevention of the first occurrence of neural-tube defects by periconceptional vitamin supplementation
Randomized trial demonstrating periconceptional folic-acid-containing supplementation prevented first-occurrence (not just recurrent) neural-tube defects.
- De-Regil LM, Peña-Rosas JP, Fernández-Gaxiola AC, Rayco-Solon P. Effects and safety of periconceptional oral folate supplementation for preventing birth defects. Cochrane Database Syst Rev. 2015;(12):CD007950.Effects and safety of periconceptional oral folate supplementation for preventing birth defects
Cochrane review concluding folic acid supplementation before and in early pregnancy substantially reduces neural-tube defects, with a good safety profile.
- Honein MA, Paulozzi LJ, Mathews TJ, Erickson JD, Wong LY. Impact of folic acid fortification of the US food supply on the occurrence of neural tube defects. JAMA. 2001;285(23):2981-2986.Impact of folic acid fortification of the US food supply on the occurrence of neural tube defects
Population data showing mandatory folic acid fortification of US grains was followed by a roughly 19-26% decline in neural-tube-defect birth prevalence.
- Prinz-Langenohl R, Brämswig S, Tobolski O, et al. [6S]-5-methyltetrahydrofolate increases plasma folate more effectively than folic acid in women with the homozygous or wild-type 677C-->T polymorphism of methylenetetrahydrofolate reductase. Br J Pharmacol. 2009;158(8):2014-2021.[6S]-5-methyltetrahydrofolate increases plasma folate more effectively than folic acid in women with the homozygous or wild-type 677C>T polymorphism of MTHFR
Methylfolate raised plasma folate somewhat more than folic acid regardless of MTHFR genotype — a blood-level (biomarker) advantage, not an outcome benefit like NTD prevention.