Supplement analysis backed by scientific evidence · PT

← All supplements
Limited evidenceStress & mood

L-Methylfolate

L-methylfolate is the bioactive form of folate, heavily marketed to people with MTHFR variants and treatment-resistant depression. The depression data come from a couple of small industry trials with modest effects, and it has never been shown clinically superior to ordinary folic acid.

What the science says

  • Augments antidepressants in SSRI-resistant depression Limited evidence

    Two sequential parallel-comparison RCTs (n=148 and n=75) found adjunctive L-methylfolate 15 mg/day produced a higher response rate than placebo (32.3% vs 14.6%) with an effect size around 0.6, while 7.5 mg/day did not separate from placebo. Both trials were manufacturer-sponsored, small, and used an unusual design; a broader systematic review of folate in unipolar depression concluded the overall evidence for folate augmentation is weak and prone to bias.

  • Is superior to folic acid for people with MTHFR C677T variants Limited evidence

    L-methylfolate bypasses the MTHFR enzyme step, which is a sound mechanistic argument, but no adequately powered trial has shown better clinical outcomes than folic acid in MTHFR carriers. Most 677T carriers achieve normal folate and homocysteine status on ordinary folic acid, and routine MTHFR genotyping is explicitly discouraged by major genetics societies.

  • Raises red blood cell folate and lowers homocysteine Moderate evidence

    Head-to-head bioavailability studies show L-methylfolate raises plasma and red cell folate at least as effectively as equimolar folic acid, and it does not generate unmetabolised folic acid in serum. That is a real biochemical advantage; whether it translates into any clinical benefit is unestablished.

  • Prevents neural tube defects Limited evidence

    Every trial demonstrating NTD prevention used folic acid, not L-methylfolate. Extrapolation is plausible but untested, and for pregnancy planning the evidence-based choice remains folic acid at 400-800 mcg/day.

Dosage & safety

Studied doseDepression augmentation trials used 15 mg/day of L-methylfolate (as the prescription medical food Deplin); 7.5 mg/day was ineffective. General supplemental doses are 400-1,000 mcg/day, equivalent to standard folate intake. Watch the labelling: products list L-5-MTHF, levomefolic acid, or the calcium or glucosamine salt (Metafolin, Quatrefolic), with differing amounts of active moiety. Upper-limit guidance is set for folic acid rather than methylfolate, but there is no reason to exceed 1 mg/day outside a supervised depression protocol.
SafetyGenerally well tolerated; reported effects include irritability, insomnia, anxiety and gastrointestinal upset, particularly at the 15 mg dose. Like folic acid, it can correct the anaemia of vitamin B12 deficiency while neurological damage continues — check B12 first. Reduces the effect of methotrexate as an antineoplastic and interacts with antiepileptics (phenytoin, carbamazepine, valproate) and capecitabine/fluorouracil. In the US the 15 mg product is regulated as a prescription medical food. It is substantially more expensive than folic acid, which is the honest practical objection: you are paying a premium for a mechanism, not for demonstrated superiority.

Scientific references

Where to buy

Metabolic Maintenance, L-Methylfolate, 15 mg, 60 Vegetarian Capsules

View on iHerb

Referral link — this site may earn a commission on purchases.

Related in Stress & mood