L-Methionine: Benefits, Dosage, Contraindications
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Amino acids
Indications
Rating methodology
EFSA approval.
Fetal Development ✪✪✪✪✪
Methionine is essential for fetal development due to its involvement in homocysteine metabolism and S-adenosylmethionine (SAM) synthesis, a crucial methyl group donor for DNA methylation and genetic regulation. These processes are particularly important during pregnancy to support organ growth and development in the fetus. Epidemiological research has highlighted that a high dietary intake of methionine during pregnancy is associated with a significant reduction in the risk of neural tube defects, such as spina bifida and anencephaly, compared to insufficient intake. These protective effects are enhanced by interactions between methionine and other nutrients involved in homocysteine metabolism, like folate, vitamin B12, and vitamin B6.
Posologie
Oral
19 mg/kg
Synergies
Breast Cancer ✪✪✪✪✪
A meta-analysis suggested that a high dietary intake of methionine might reduce breast cancer risk by 6%, especially in postmenopausal women, with an additional 4% reduction for each gram of methionine added daily. However, a more recent meta-analysis, including a large cohort (300,000 participants), found no significant association between methionine intake and breast cancer risk.
Posologie
Oral
19 mg/kg
Hair Beauty ✪✪✪✪✪
Methionine, an essential amino acid, is a component of keratin, the main protein in hair. It plays a central role in hair growth and strength by supporting sulfur production, an important element for hair follicle structure. A randomized clinical study evaluated the effectiveness of a supplement combining methionine, cysteine, taurine, iron, selenium, and marine collagen (300 mg per day) in individuals suffering from androgenetic alopecia or hair loss related to stress (telogen effluvium). After 12 weeks, subjects taking this supplement alongside standard hair loss treatments (such as minoxidil) showed significant improvements in hair density and thickness compared to treatments alone. These results confirm the interest in methionine supplementation to promote better hair health.
Posologie
Oral
19 mg/kg
Properties
Antioxidant
Methionine helps protect against oxidative stress by participating in the production of glutathione, a major antioxidant in the body. Glutathione neutralizes free radicals and protects cells against oxidative damage, which is involved in cellular aging and the development of many chronic diseases, including cancers and neurodegenerative diseases.
Anticancer
High dietary intake of methionine is associated with a significant reduction in the risk of colorectal, breast, and pancreatic cancers. This benefit is linked to its role in the synthesis of S-adenosylmethionine (SAM), a crucial methyl group donor for DNA methylation. This process protects DNA against mutations and promotes DNA repair. However, many tumors depend on exogenous methionine for their growth. This dependency, absent in normal cells, has led to the exploration of methionine restriction as a therapeutic strategy. Preliminary clinical trials have shown that a dietary restriction of methionine is safe and potentially effective in patients with advanced cancers, with promising results such as a 25% reduction in prostate-specific antigen (PSA) in a patient with prostate cancer after 12 weeks of restrictive diet. Finally, in vitro studies show that methionine restriction activates pro-apoptotic pathways, such as the JNK1 kinase, leading to the death of tumor cells. These data suggest the dual role of methionine: a key nutrient for cancer prevention via methylation and a potential therapeutic target to limit tumor growth in certain cases.
Usages associés
Hepato-protective
Methionine is essential for liver health due to its role in detoxification and lipid metabolism. Increased production of glutathione helps the liver neutralize toxins, including heavy metals. It also participates in the synthesis of lipoproteins, a factor in preventing hepatic steatosis. In liver diseases, methionine promotes the regeneration of liver cells and reduces damage induced by toxic agents or an unbalanced diet.
Safety dosage
Adult: 19 mg/kg
The recommended nutritional intake (RNI) for methionine plus cysteine is 19 mg/kg/day.
Pregnant Women: 25 mg/kg
During pregnancy, the recommended intake is 25 mg/kg/day.
Breastfeeding Women: 26 mg/kg
During breastfeeding, the recommended intake is 26 mg/kg/day.
Child: 19 mg/kg - 59 mg/kg
Needs vary with age: - 0-6 months: 59 mg/kg/day - 7-12 months: 43 mg/kg/day - 1-3 years: 28 mg/kg/day - 4-8 years: 22 mg/kg/day - 9-13 years: 22 mg/kg/day (boys), 21 mg/kg/day (girls) - 14-18 years: 21 mg/kg/day (boys), 19 mg/kg/day (girls)
Contraindications
Hyperhomocysteinemia: prohibited
Methionine is contraindicated for individuals with a specific genetic mutation called MTHFR C677T, which affects homocysteine metabolism. In these patients, taking methionine might increase homocysteine levels and heighten the risk of vascular problems.
