Last verified: 17 days ago
L-Methionine
Also known as: methionine, L-Met, S-adenosyl-L-methionine precursor, SAMe precursor
Evidence under review. — Not yet rated
Essential amino acid with antioxidant properties; limited human evidence for most supplement claims.
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What it does
L-Methionine is an essential amino acid your body cannot make on its own — you must get it from food or supplements. It serves as a building block for proteins and is a precursor to...
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Evidence quality
Evidence base hasn't been formally rated yet. See research below.
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Clinical dose
No established dose from provided studies
What the Science Says
L-Methionine is an essential amino acid your body cannot make on its own — you must get it from food or supplements. It serves as a building block for proteins and is a precursor to S-adenosyl-L-methionine (SAMe), a key molecule involved in dozens of biochemical reactions including DNA methylation and antioxidant production. In rat studies, L-Methionine showed protective effects against drug-induced heart damage by reducing oxidative stress and inflammation, but human clinical evidence for supplementation is very limited.
What It Doesn't Do
Not proven to build muscle or boost athletic performance in humans. No human evidence it directly protects your heart. Don't confuse it with SAMe — they are related but not the same supplement. No evidence it detoxifies the liver on its own in humans. The rat studies showing cardioprotection have not been replicated in people.
Evidence-Based Benefits
Reduced heart damage markers caused by methotrexate in a rat model.
Weak EvidenceEffective at: 300–400 mg/kg in rats (no human equivalent established)
Supporting studies (click to view on PubMed):
Reduced oxidative stress markers and inflammation in rat cardiac tissue.
Weak EvidenceEffective at: 300–400 mg/kg in rats (no human equivalent established)
Supporting studies (click to view on PubMed):
Absorption & Bioavailability
Unknown from provided studies — no human pharmacokinetic data in the provided papers
Red Flags to Watch For
- Most evidence comes from animal (rat) studies, not human clinical trials
- High doses of methionine may raise homocysteine levels, a cardiovascular risk factor — not addressed in provided studies
- Often found in multi-ingredient products (e.g., MetioNac®), making it impossible to isolate L-Methionine's individual effect
- No established safe upper limit for supplemental L-Methionine in humans based on provided data
Products Containing L-Methionine
See how L-Methionine is used in these analyzed products:
Elm & Rye Vegan Protein Blend
Supplement
Thorne Amino Complex Berry Powder NSF
Supplement
Double Wood Supplements Essential Amino Acids
Supplement
Optimum Nutrition 100% Gold Standard Whey
Supplement
Peak Performance Mood Support Capsules
Supplement
Swolverine INTRA
Supplement
Everyday Dose
Supplement
Frequently Asked Questions
What does L-Methionine do?
Essential amino acid with antioxidant properties; limited human evidence for most supplement claims.
What is the effective dose of L-Methionine?
No established dose from provided studies
Is L-Methionine safe?
Most evidence comes from animal (rat) studies, not human clinical trials
What doesn't L-Methionine do?
Not proven to build muscle or boost athletic performance in humans.
Research Sources
- PubMed
- NIH DSLD
This information is for educational purposes only and is not medical advice. Always consult a healthcare professional before starting any supplement regimen. Last updated: 2026-05-25