Nutrition Basics: Amino Acids - Methionine

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Nutrition Basics: Amino Acids - Methionine

http://www.moondragon.org/health/nutritionbasics/aminoacids/methionine.html

 

" For Informational Use Only "

For more detailed information contact your health care provider

about options that may be available for your specific situation.

 

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 accelerage 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.

 

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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.

 

 

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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 adaquate 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

posttranslational protein-modifying events that often occur where methionine and

several other N-terminal amino acids are removed from the protein.

 

 

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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.

 

 

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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.

 

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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 B12, may increase the rate of

conversion of methionine to homocysteine - both these theories have not been

proven in

humans.

 

 

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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 B6, 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.