Methionine
METHIONINE is an essential amino acid that cannot be synthesized in the body, but must be obtained from food sources or from dietary supplements. Methionine is a precursor for the other sulfur amino acids, cystine, taurine, and glutathione. It has the ability to be a methyl donor to other molecules, which is essential in formulating RNA and DNA. Methionine is necessary for the absorption, transportation, and bioavailability of selenium. In order to be properly utilized, methionine requires the help of its cofactors -- Vitamins B6, B12, Bc, choline, folic acid, and magnesium.
Methionine is an antioxidant and, because it has a methyl group, it can combine with active free radicals. However, its derivative, homocysteine, is a powerful oxidant. Adequate levels of B6 are required to allow this harmful compound to be reconverted into an antioxidant substance called cystathione. A high meat intake with an inadequate supply of B6 would produce this type of situation, as would high methionine supplementation without additional B6. The result is cardiovascular disease. Methionine is important in the formation of blood proteins, globulins, and albumins. It also assists in the breakdown of fats, preventing their buildup in the liver and arteries, which can obstruct blood flow to the brain, heart, and kidneys.
Methionine is important in the treatment of rheumatic fever and pregnancy-induced toxemia. With the help of choline and folic acid, methionine is a chelator for heavy metals and helps remove them from the body. Methionine is also used as an antidote in paracetamol poisoning -- a pain killer available by prescription and in over-the-counter analgesics -- and to lower urinary pH, making it more acidic.
The body uses methionine to derive a brain food called choline. Therefore, choline or lecithin (which is high in choline) should be added to the diet so that the supply of methionine is not depleted. Beans are low in methionine but rich in lysine; and, since most grains are low in lysine and rich in methionine, combining beans and grains will give a full complement of amino acids.
Methionine deficiency causes the liver to metabolize only histidine to form, resulting in an incomplete form of folic acid. From this, researchers conclude that methionine is a key factor in regulating the availability of folate. When methionine levels are low, folate becomes trapped in the liver as 5-methyl-tetrahydrofolate, causing a temporary folic acid deficiency since this form cannot be used. This is also seen in Vitamin B12 deficiencies and may be an important factor in all allergy and some anemia patients.
Since 1970, methionine deficiencies have been attributed to such ailments as toxemia, childhood rheumatic fever, muscle paralysis, hair loss, depression, schizophrenia, Parkinson's, liver deterioration, and impaired growth.
Food sources include beans, eggs, fish, garlic, lentils, meat, onions, soybeans, seeds, yogurt.
Other names for Methionine include: MET, amino acid M, and 2-amino-4(methylthio)-buanoic acid.
