L-Methionine

Methionine is one of the 20 amino acids commonly found in animal proteins. Methionine is an essential amino acid. Methionine supplies sulfur and other compounds required by the body for normal metabolism and growth. Methionine also belongs to a group of compounds called lipotropics; others in this group include choline, inositol, and betaine.
Methionine forms S-adenosyl methionine (SAMe). S-adenosyl methionine contributes to the synthesis of many important substances, including adrenaline and choline.
SAMe is involved in the synthesis of creatine, adrenaline, melatonin and the polyamines spermine and spermidine, among several other substances. 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. Methionine is especially important for those suffering from oestrogen dominance, where the amount of oestrogen in the body is excessively high when compared to its opposing hormone progesterone. L-Methionine is believed to help by increasing removal of excess oestrogen from the liver.
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.
Meat, fish, and dairy products are all excellent sources of methionine. L-methionine is also found in fruits and vegetables, but not as abundantly. Small amounts of free L-methionine occur in vegetables, vegetable juices and fermented foods. Vegetarians can obtain methionine from whole grains. L-Methionine is found only in very small amounts in legumes (beans and peas) which means that legumes and grains need to be combined to give adequate protein (grains are low in L-lysine and legumes are high, so the two types of food fill in each others' deficiencies).
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.
Most people consume plenty of methionine through a typical diet. Lower intakes during pregnancy have been associated with neural tube defects in newborns. Methionine deficiency leads to reduced growth rate with the development of bilateral cataracts. It is felt that deficiencies of vitamin A and riboflavin also play a role in this lesion. Methionine deficiency can cause apathy, loss of pigmentation in hair, oedema, lethargy, liver damage, muscle loss, fat loss, skin lesions, weakness, and slowed growth in children.
Excessive methionine intake, together with inadequate intake of folic acid, vitamin B6, and vitamin B12, can increase the conversion of methionine to homocysteine. Homocysteine has been linked to atherosclerosis. L-methionine supplementation should be avoided by those with neoplastic disease and elevated homocysteine 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. There are no known drug or nutrient interactions associated with methionine.