Vitamin supplements guide   Vitamins & health supplements guide

Methionine quick review
Description: an essential sulfur-containing amino acid, its sulfur is non reactive.
Health benefits: helps remove fat from the liver, helps reduce histamine levels, supplies sulfur and other compounds required by the body for normal metabolism and growth.

Sources & dosage: meat, fish, and dairy products, fruits, vegetables, fermented foods. recommended daily intake is 13 mg per kg (body weight) for adults.
Deficiency symptoms: apathy, loss of pigmentation in hair, edema, lethargy, liver damage, muscle loss, fat loss, skin lesions, weakness, and slowed growth in children.
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Methionine, organic compound, one of the 20 amino acids commonly found in animal proteins. Methionine is one of the several essential amino acids needed in the diet; the human body cannot synthesize it from simpler metabolites. Methionine supplies sulfur and other compounds required by the body for normal metabolism and growth. It is an important source of dietary sulfur. Methionine also belongs to a group of compounds called lipotropics; others in this group include choline, inositol, and betaine. Methionine is one of only two amino acids encoded by just one codon (AUG) in the standard genetic code (tryptophan, encoded by UGG, is the other). L-methionine is a sulfur-containing amino acid that is minimally soluble in water. Its sulfur is non reactive.


Methionine functions, uses, and health benefits

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.


Dietary sources of methionine

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.


Methionine dosage, intake

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.


Methionine deficiency

Methionine deficiency is caused by an abundance of the ß-chain of ß-conglycinin, a seed storage protein that lacks methionine. Methionine deficiency is associated with a deficiency of S-adenosylmethionine which acts as an endogenous anti-depressant. 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 (primarily in salmonids) leads to reduced growth rate with the development of bilateral cataracts. (Zinc, and cystine deficiencies can also cause cataracts) It is felt that deficiencies of vitamin A and riboflavin also play a role in this lesion. Methionine deficiency causes the liver to metabolize only histidine to form, resulting in an incomplete form of folic acid. Methionine deficiency can cause apathy, loss of pigmentation in hair, edema, lethargy, liver damage, muscle loss, fat loss, skin lesions, weakness, and slowed growth in children.

Toxicity, side effects, interactions, and contraindications

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. There are no known drug or nutrient interactions associated with methionine.