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Methionine is a sulfur containing essential amino acid and was first isolated in 1922 from casein and belongs to a group of compounds called lipotropics - the others in this group include choline, inositol, and betaine. It is important in the process of methylation where methyl is added to compounds as well as being a precursor to the amino acids cystine and cysteine.
Methionine is an essential amino acid that assists in the breakdown of fats, thus helping to prevent a buildup of fat in the liver, is often included in liver-detoxifying products called lipotropic combinations. These formulations are believed to accelerate the flow of bile and cell-damaging toxins away from the liver. It also helps prevent buildup of fat in the arteries that might obstruct blood flow to the brain, heart, and kidneys.
The synthesis of the amino acids cysteine and taurine may depend on the availability of methionine. This amino acid helps the digestive system; helps to detoxify harmful agents such as lead and other heavy metals; helps diminish muscle weakness, prevent brittle hair, and protect against radiation; and is beneficial for people with osteoporosis or chemical allergies. It is useful also in the treatment of rheumatic fever and toxemia of pregnancy.
Methionine is a powerful antioxidant. It is a good source of sulfur, which inactivates free radicals. Sulfur, a mineral, helps to maintain healthy skin tone, well-conditioned hair, and strong nails. It is also good for people with Gilbert's syndrome, an anomaly of liver function, and is required for the synthesis of nucleic acids, collagen, and proteins found in every cell of the body.
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. The nutrient is believed to help by expediting the removal of excess estrogen from the liver. The bleeding, cramps, pain, and other complications of this common ailment may subside as a result. More research is needed, however.
It is beneficial for women who take oral contraceptives because it promotes the excretion of estrogen. It reduces the level of histamine in the body, which can be useful for people with schizophrenia, whose histamine levels are typically higher than normal. Some studies have also indicated that methionine might improve memory recall.
As levels of toxic substances in the body increase, the need for methionine increases. The body can convert methionine into the amino acid cysteine, a precursor of glutathione. Methionine thus protects glutathione; it helps prevent glutathione depletion if the body is overlooked with toxins. Since glutathione is a key neutralizer of toxins in the liver, this protects the liver from the damaging effects of toxic compounds.
Sources
An essential amino acid, methionine is not synthesized in the body, and so must be obtained from food sources or from dietary supplements. Good food sources of methionine include beans, eggs, fish, garlic, lentils, meat (chicken & beef), onions, soybeans, seeds, cheddar cheese and yogurt. Because the body uses methionine to derive a brain food called choline, it is wise to supplement the diet with choline or lecithin (which is high in choline) to ensure that the supply of methionine is not depleted. It is best to balance methionine with choline and inositol.
Molecular Description
Methionine is an important amino acid that helps to initiate translation of messenger RNA by being the first amino acid incorporated into the N-terminal position of all proteins. This sulfur-containing amino acid is also the source of sulfur for cysteine in animals and man. In that regard, methionine is considered an essential amino acid whereas cysteine is not, so cysteine is nonessential only as long as the diet contains adequate amounts of methionine. The terminal methyl group of the methionine side chain often participates in biochemical methyl transfer reactions making methionine a member of the "methyl donor" class of biochemicals. On a molar basis, methionine is incorporated into proteins and enzymes at the rate of 1.7 percent, but this is partially due to post-translational protein-modifying events that often occur where methionine and several other N-terminal amino acids are removed from the protein.
Methionine Deficiency
Severe deficiency may manifest in dementia, while lesser deficiencies may be known by symptoms like fatty liver, slow growth, weakness, edema and skin lesions.
Supplements may be required for people with liver problems, pancreatitis, HIV/AIDS as well as Parkinson's disease may consider obtaining more methionine, after consultation with their health professional, and older people may also benefit from a slightly higher intake of this nutrient.
Women on birth control pills could also look at this nutrient, since it promotes the excretion of estrogen. People suffering from schizophrenia could investigate taking extra methionine since it reduces the level of histidine in the body, a level normally higher in people suffering from schizophrenia.
Dosage
The RDA dosage for ornithine has not been established. However for optimal health, 50 mg of L-methionine is recommended per day.In human research involving ornithine, several grams are typically used per day, sometimes combined with arginine.
Toxicity & Symptoms of High Intake
It has been suggested that a high intake of methionine, in the presence of B vitamin deficiencies, may increase the risk for arteriosclerosis (hardening of the arteries) by increasing blood levels of cholesterol and a compound called homocysteine; and that excessive methionine intake, with an inadequate intake of folic acid, vitamin B-6 and vitamin B-12, may increase the rate of conversion of methionine to homocysteine - both these theories have not been proven in humans.
Interactions & Cautions
There are no known drug or nutrient interactions associated with methionine.
Avoid taking more than the commonly recommended amount of methionine. This is particularly important if your diet is low in folic acid, vitamin B-6, or vitamin B-12, because this could increase the conversion of methionine to homocysteine. Homocysteine is a potentially harmful blood fat that has been linked to atherosclerosis (hardening of the arteries).
If you have any serious illness or are pregnant, only take an amino acid such as methionine after consulting your health care provider.
To be safe, never take methionine, or any single amino acid for that matter, for longer than three months unless you are under the direction of a health care provider familiar with its use.
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METHIONINE / L-METHIONINE SUPPLEMENT PRODUCTS
L-Methionine Plus B-6, NOW Foods, 500 mg Plus 10 mg, 100 Caps
L-Methionine is an essential sulfur amino acid. The body cannot produce L-Methionine, which must be obtained from food or supplement sources.
SAM-e, Enteric Coated, NOW Foods, 100 mg, 30 Tabs
SAM-e was discovered in 1952 in Italy and has been researched and manufactured there. SAM-e works closely with folic acid and vitamin B-12.
SAM-e with B Vitamin Cofactors, Vegetarian, Enteric Coated, NOW Foods, 200 mg, 60 Tabs
Important for the production of glutathione, this powerful free radical scavenger defends the body from toxic agents and is necessary for liver detoxification.
Methionine / L-Methionine / S Adenosol Methionine (SAM-e) Supplements & Products
Methionine / L-Methionine / S Adenosol Methionine (SAM-e) Information
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