Methylfolate (L-5-MTHF)

What Methylfolate Is

Folate from food and folic acid from supplements both have to be converted before they can do their main job. The final product is L-5-methyltetrahydrofolate (L-5-MTHF), which hands a methyl group to homocysteine — with vitamin B12 as the cofactor — and turns it back into methionine. The last conversion step is performed by the MTHFR enzyme. Methylfolate supplements supply that end product directly, sold as calcium or glucosamine salts.

The marketing case rests on the MTHFR 677T variant, which slows that enzyme. The evidence on what that variant does — and does not — mean is in MTHFR Variants: What the Evidence Actually Supports.

Methylfolate vs Folic Acid

Four randomised trials compared the two directly:

• Homocysteine, low dose (24 weeks, n = 167): about 100 mcg of L-MTHF lowered homocysteine by 14.6% versus 9.3% for folic acid — a modest advantage.
• Homocysteine, standard dose (24 weeks, n = 144): 400 mcg folic acid, 416 mcg 5-MTHF and 208 mcg 5-MTHF lowered homocysteine equally.
• By MTHFR genotype (8 weeks, n = 160): folic acid lowered homocysteine by at least 13% in every genotype and by 20% in TT carriers. The racemic MTHF used in that trial was less effective in CC and CT women.
• Red-cell folate: rose more with 5-MTHF than folic acid over 24 weeks.

A pharmacokinetic study in TT and CC women found 5-MTHF produced higher and faster peaks of plasma folate in both genotypes, and that plasma folate was essentially all 5-MTHF regardless of which form was swallowed. Methylfolate does avoid unmetabolised folic acid in blood, which appears after single doses above roughly 200 mcg; whether that matters for health is unresolved.

Bottom line: methylfolate is equal or slightly better on blood markers. It has no clinical-outcome advantage, and folic acid works in MTHFR TT carriers.

Pregnancy

Neural tube defect prevention is the strongest evidence in all of nutrition, and it is folic acid evidence. A Cochrane review of five trials found folic acid cut neural tube defects by 69% (RR 0.31). No trial has tested methylfolate against this outcome. Methylfolate raises red-cell folate at least as well, so it is a reasonable alternative for someone who prefers it — but an MTHFR result is not a reason to drop the form the evidence is built on.

Dose and Upper Limit

0.4 mg daily, with B12, covers almost every non-pharmacological use; in the homocysteine meta-analyses, 0.4 mg of folate delivered about 90% of the maximum effect and 0.8 mg all of it. The EU upper limit of 1 mg/day, set in 2023, explicitly includes methylfolate as well as folic acid, because the risk being guarded against — masking B12 deficiency — applies to both.

Products of 7.5–15 mg are sold as add-on treatments for depression. Those are pharmacological doses with mixed trial evidence and belong under psychiatric supervision, not in a methylation stack.

Where It Fits

Methylfolate is Layer 2 of the Methylation Support Protocol, used after B12 has been checked and corrected, and only if homocysteine is still raised or folate is low.

Related Research

• MTHFR Variants: What the Evidence Actually Supports
• Homocysteine: What Your Level Means and How to Lower It
• The Methylation Support Protocol: Test, Then Target
• Vitamin B12
• Riboflavin