What is L-Methionine (L-Methionine)?
L-methionine is an essential, sulfur-containing amino acid that cannot be synthesized by the body. In addition to being the start amino acid (start codon) for protein synthesis, it plays a central role in methylation reactions as the body's primary methyl donor via S-adenosylmethionine (SAMe). It converts to cysteine and glutathione via the transsulfuration pathway and is critical in liver metabolism.
- CAS number: 63-68-3
- Molecular formula: C₅H₁₁NO₂S
What is L-Methionine Used For? Why is it Used?
L-methionine is an essential, sulfur-containing amino acid and plays an indispensable role in methylation (SAMe) and glutathione/cysteine synthesis. It is a key component in feed and plant-based protein supplementation; its biochemical roles in the liver and antioxidant pathways are clear, but there is no robust evidence for performance benefits specific to athletes, and excessive intake should be avoided.
Usage as Sports Nutrition
The following information is based on sports nutrition research (ISSN position stands, randomized controlled trials, and meta-analyses); the level of evidence is clearly stated for each item.
- Sulfur-containing amino acid balance (exercise): Exhaustion exercise alters sulfur-containing amino acid metabolism; it has been shown that post-exercise protein+carbohydrate intake affects the methionine/homocysteine ratio and glutathione in elite cyclists. No direct ergogenic performance benefit has been proven (honest).
- Glutathione (antioxidant) precursor: Glutathione defense against exercise-induced oxidative stress depends on the presence of sulfur-containing amino acids; methionine provides sulfur to this pathway via cysteine. There is no robust RCT proving the benefit of methionine supplementation alone in athletes.
Forms and Differences
L-Methionine is offered in different forms; form selection is made based on bioavailability, stability, and intended use:
- L-Methionine (free form): Food and supplement grade L-methionine is produced via microbial fermentation or chemical synthesis. It is an essential sulfur-containing amino acid; the L-form is the biologically available one.
- DL-Methionine / Methionine hydroxy analog (feed grade): DL-methionine and methionine hydroxy analog (MHA) are commonly used in animal feed; EFSA FEEDAP evaluates these.
Usage in Dietary Supplements
- Methyl donor / SAMe pathway: Methionine is a precursor to SAMe; it provides substrate for DNA, protein, and lipid methylation as well as polyamine synthesis. Approximately half of daily methionine is metabolized in the liver.
- Liver and glutathione support: It provides sulfur for cysteine and glutathione synthesis; studies have reported that SAMe supplementation replenishes hepatic glutathione and reduces liver damage (methionine is the precursor for this).
Usage in the Food Industry
- Animal feed additive: Methionine is the first limiting amino acid in poultry and generally the second/third in swine; it is one of the most commonly used amino acids in feed enrichment (DL-methionine/MHA).
- Food/clinical protein supplementation: It is used to complete the sulfur-containing amino acid profile in plant-based formulations (especially where it is limiting in legume proteins).
Effects on Health
- Methylation (SAMe): As SAMe, it is the body's main methyl donor; DNA/protein/lipid methylation and polyamine synthesis depend on this pathway (established physiology).
- Liver metabolism and glutathione: It produces cysteine via transsulfuration; cysteine is the rate-limiting substrate for glutathione synthesis. It supports the liver's antioxidant/detoxification defense.
- Protein synthesis initiation: It is the start amino acid for mRNA translation; it is required for all protein synthesis.
Status of Health Claims (EFSA) — Transparent Information
EFSA FEEDAP has evaluated methionine and its analogs as animal feed additives. There is no authorized specific health claim for methionine in human food claims. The statements here are not claims but are based on established biochemistry. ⚠️ Warning: excessive methionine can raise homocysteine.
Usage Limits and Safety
- Typical usage dose: Typical in supplements is 0.5-2 g/day; adult requirement for sulfur-containing amino acids (methionine+cysteine) is approximately ~15 mg/kg/day
- Upper Intake Level (UL): No established UL exists; however, excessive intake should be avoided as high methionine can lead to elevated homocysteine and nausea (honest: no definitive UL, safety margin is low).
- Turkish legislation (Sports Foods / TETGK): It is used as an essential amino acid in the Turkish Food Codex; an official numerical upper limit for L-methionine could not be verified by me — the number is NOT FABRICATED, the manufacturer's Communiqué should be the basis.
Individuals with liver disease, homocystinuria, or methylation disorders, as well as pregnant women, should avoid high doses and consult a physician.
Technical Specifications
| Parameter | Value |
|---|---|
| Moisture | ≤5.0 % |
| Total Heavy Metals | ≤10 ppm |
| E. Coli | Negative in 10 g |
| Salmonella | Negative in 25 g |
| Solubility | Soluble in Water |
Scientific Studies
The following independent researches relate to the component's effect on sports performance, bioavailability, and efficacy (study types are specified):
- PubMed 23396728 — S-adenosylmethionine metabolism and liver disease
- PubMed 33375657 — Exhaustion exercise and post-exercise protein+carbohydrate supplementation affect sulfur-containing amino acids, methionine/homocysteine ratio, and glutathione concentrations in elite male cyclists
Technical Documents and Supply — Asuka Kimya
You can contact Asuka Kimya for SDS, TDS, CoA and supply conditions for L-Methionine.
References
- efsa.onlinelibrary.wiley.com
- pubmed.ncbi.nlm.nih.gov
- ncbi.nlm.nih.gov
- pubmed.ncbi.nlm.nih.gov
- pubmed.ncbi.nlm.nih.gov
The usage, sports nutrition, and health information on this page have been compiled from official legislation/institution sources (EFSA, NIH ODS, ISSN, Turkish Food Codex Sports Foods / Dietary Supplements Communiqué) and independent scientific publications (PubMed). The product is a food supplement/sports nutrition raw material; it does not aim to diagnose or treat diseases.