L-Methionine is an essential sulfur-containing amino acid that is soluble in water. It is a powerful antioxidant, assists in the breakdown of fats, and helps inactivate free radicals. Because it is an essential amino acid, it must be supplied in the diet. The recommended daily intake is 13 mg per kg or about one gram daily for adults. The actual intake is higher due to the fact that it is principally derived from dietary proteins. Cheese, eggs, fish, meat and poultry are all rich sources of L-methionine. It can also be found in fruits and vegetables, but not as abundantly.

L-methionine is part of many biochemical reactions, including the production of S-adenosylmethionine (SAM or SAMe), L-cysteine, gluthione, taurine, and sulfate. SAM is involved in the synthesis of creatine, epinephrine, melatonin and the polymines spermine and spermidine, among several other substances.
Since L-methionine is a glycogenic amino acid, it may participate in the formation of D-glucose and glycogen. It can help reduce the liver-toxic effects of such hepatotoxins as acetaminophen and methotrexate. Some suggest that acetaminophen products should contain L-methionine.

What is L-Methionine ?
An essential amino acid that is not synthesized by the body and must be obtained from food or supplements. It is a powerful antioxidant and a good source of sulfur, which neutralizes free radicals and helps prevent skin, coat and nail problems.

Where it is found
Whole grains are high in Methionine. It is also found in meat and poultry, and milk and milk products. Leafy vegetables, peaches and grapes are also the source of methionine.

Benefits / uses
Methionine reacts with adenosine triphosphate to form S-adenosyl methionine. S-adenosyl methionine is the principal methyl donor in the body and contributes to the synthesis of many important substances, including epinephrine and choline. SAMe is involved in the synthesis of creatine, epinephrine, melatonin and the polyamines spermine and spermidine, among several other substances. Since methionine is the only essential amino acid not present in significant amounts of soybeans, it is produced commercially as an additive for soybean meal. Methionine is incorporated into the N-terminal position of all proteins in eukaryotes and archaea. Methionine plays a role in cysteine, carnitine and taurine synthesis by the transsulfuration pathway, lecithin production, the synthesis of phosphatidylcholine and other phospholipids.

Methionine in lipotropic combinations has been proposed for treating endometriosis, a condition in which patches of endometrial tissue from the uterine lining grow outside the uterus. Methionine is an especially important nutrient beneficial for those suffering from estrogen dominance, where the amount of estrogen in the body is excessively high when compared to its opposing hormone called progesterone. The nutrient is believed to help by expediting the removal of excess estrogen from the liver.

Methionine is both an antioxidant and lipotrope, meaning it helps remove fat from the liver. Methionine contributes to the hydrophobicity of a protein. Methionine controls the level of beneficial sulfur-containing compounds in the body. These sulfur-containing compounds are in turn vital for defending against toxic compounds like heavy metals in the liver. Methionine helps reduce histamine levels, which are amino acids that control dilation of blood vessels and influence brain function.

Doses
Amino acid requirements vary according to body weight. L-methionine supplements should only be taken with a physician's recommendation. According to the Food and Agriculture Organization of the United Nations (FAO) and World Health Organization (WHO), recommended daily L-methionine intake is 13 mg per kg or about one gram daily for adults. During methionine supplementation, intake of taurine, cysteine, and other sulfur containing amino acids, as well as B6 and folic acid should also be included.

Possible Side effects / Precautions / Possible Interactions:
Excessive methionine intake, together with inadequate intake of folic acid, vitamin B6, and vitamin B12, can increase the conversion of methionine to homocysteine. Homocysteine is a potentially harmful blood fat that has been linked to atherosclerosis (Hardening of the arteries). L-methionine supplementation should be avoided by those with neoplastic disease and elevated homocysteine levels and used with caution in those with coronary heart disease. L-methionine supplements should be avoided by pregnant women and nursing mothers unless they are prescribed by a physician.

Research studies / References