Folate (vitamin B9) is essential for one-carbon metabolism — the chemistry that builds DNA, methylates genes, and recycles homocysteine. The active form (5-methyltetrahydrofolate, 5-MTHF) is what the body actually uses, which is why MTHFR variants matter for some people.
Strong evidence · Last reviewed:
Key facts
Daily needs
400 mcg DFE adults · 600 mcg pregnancy
Active form
5-MTHF (L-methylfolate)
Key gene
MTHFR (C677T, A1298C)
Best food sources
Leafy greens — spinach, romaine, arugula
Legumes — lentils, chickpeas, black beans
Liver (highest density)
Asparagus, broccoli, Brussels sprouts
Avocado, citrus, fortified grains
Folate vs folic acid vs methylfolate
Food folate — natural mix, converted to 5-MTHF before use
Folic acid — synthetic, requires MTHFR to convert efficiently
5-MTHF (L-methylfolate) — the active form; bypasses MTHFR
Folinic acid (calcium folinate) — gentler alternative for methyl-sensitive users
When deficiency matters most
Preconception and pregnancy — neural tube defect prevention
MTHFR carriers with elevated homocysteine
Heavy alcohol use, certain anticonvulsants, methotrexate
Malabsorption (celiac, IBD)
Related in the knowledge graph
Genes
MTHFR — MTHFR encodes the enzyme that produces active folate (5-MTHF) from dietary and supplemental folate. Strong evidence
Supplements
L-Methylfolate — L-methylfolate is the supplemental form of the active folate end-product. Strong evidence
FAQ
Is folic acid bad for MTHFR carriers?
Not at typical food-fortification doses. At higher supplemental doses, unmetabolized folic acid can accumulate; 5-MTHF or folinic acid avoid that issue.
How much folate do I need during pregnancy?
Major guidelines recommend at least 600 mcg DFE/day from diet plus a prenatal containing folate or 5-MTHF, starting before conception.
References
Greenberg et al., Rev Obstet Gynecol 2011 — PMID 22132188. 5-MTHF is appropriate preconception folate for women with MTHFR variants.