5-MTHF
Research Reliability -
The bioactive form of folate that supports methylation, mood, prenatal health, and cardiovascular function.
Appetite
Mood
Sleep
5-MTHF
Description
5-MTHF (methyltetrahydrofolate) is the active, ready-to-use form of folate that bypasses the MTHFR enzyme conversion step required by synthetic folic acid. It is essential for single-carbon metabolism, DNA synthesis, and neurotransmitter production. Individuals with MTHFR polymorphisms cannot efficiently convert folic acid and should use this form. It is critical during pregnancy for neural tube development, and supports homocysteine regulation, mood stability, and cardiovascular health across all life stages.
Effects
First 2 weeks
subtle
Weeks 2–4
Ongoing
How It Feels
Most people feel little. Those with an MTHFR variant sometimes notice a real mood or energy shift, since this is the already-active form of folate. A small subset feels wired or irritable, which signals the dose is too high.
Evidence
Evidence Strength
Moderate (some human RCTs)
Caveats
Best-supported as an adjunct in specific depression/deficiency contexts, not as a general cognitive enhancer.
Usage
Commonly Referenced Starting Amount
400 mcg DFE/day
Commonly Referenced Amount
400–1,000 mcg DFE/day covers RDA through commonly supplemented doses
Referenced Upper Limit
1,000 mcg/day is the IOM upper limit, set on synthetic folic acid's risk of masking B12 deficiency; methylfolate is presumed to carry a similar caution
Onset
2–4 weeks
Biomarkers to Track
Subjective
(Daily)
Mood and emotional resilience
Energy and mental clarity (1–10)
Sleep quality score
Objective
(Quarterly)
Homocysteine level
RBC folate level
MTHFR genotype (once, baseline)
Generally safe as the active folate form. A subset feels wired or irritable, a sign of overmethylation.
People on certain chemotherapy or seizure medications should check first.
Starting at a high dose rather than easing in, and ignoring irritability as a cue to lower it.
Disclaimer
This information is for educational purposes only and is not medical advice. It is not intended to diagnose, treat, cure, or prevent any disease. Consult a qualified healthcare provider before starting any new supplement, especially if you are pregnant, nursing, taking medication, or managing a health condition.
Papakostas GI et al. (2012). American Journal of Psychiatry. RCT (L-methylfolate as antidepressant adjunct). PMID: 23212058.
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