Folate (5-MTHF) — The Active Methyl Donor
Folate (5-MTHF) is the active, bioavailable form of vitamin B9, essential for DNA synthesis, repair, and the methylation cycle. By efficiently lowering homocysteine and supporting epigenetic maintenance, it plays a critical role in cardiovascular health, cognitive function, and cellular longevity.
Mechanism of Action
5-Methyltetrahydrofolate (5-MTHF) is the biologically active form of folate and the primary methyl donor in the one-carbon metabolism cycle. It donates a methyl group to homocysteine to form methionine, a reaction catalysed by methionine synthase and requiring vitamin B12. Methionine is subsequently converted to S-adenosylmethionine (SAMe), the universal methyl donor for DNA, RNA, and protein methylation. By maintaining efficient methylation and keeping homocysteine levels low, 5-MTHF supports epigenetic regulation, cardiovascular health, and neurotransmitter synthesis.
Human Trial Evidence
Multiple human trials demonstrate that 5-MTHF effectively lowers plasma homocysteine levels, a known cardiovascular risk factor, particularly in individuals with MTHFR polymorphisms. Clinical studies also show it improves endothelial function and vascular superoxide production. High-dose L-methylfolate (up to 15 mg/day) has been shown in randomised trials to improve symptoms in treatment-resistant depression.
Dosing Protocol
400–1,000 mcg/day is the standard supplemental range, with doses up to 15 mg/day used clinically for treatment-resistant depression. Best taken in the morning. Unlike folic acid, 5-MTHF does not require enzymatic conversion by MTHFR and can be utilised directly.
Safety & Contraindications
Generally well tolerated at standard doses. High doses may mask vitamin B12 deficiency (though less likely than with synthetic folic acid); therefore, concurrent B12 supplementation is often recommended. Over-methylation symptoms such as anxiety, irritability, or insomnia can occur in sensitive individuals.