The Function of Methionine in the Body

Methionine is a sulfur-containing essential amino acid that plays a crucial role in metabolism. As an essential amino acid, methionine cannot be synthesized in the body and must be obtained from foods such as sesame seeds, Brazil nuts, fish and meat. Methionine deficiency is rare, but when present it may lead to reduced growth rate along with liver damage, muscle loss, edema, skin lesions and lethargy. Supplements of the amino acid are prescribed to treat a deficiency.

Antioxidant Activity

Methionine is a powerful antioxidant, and the sulfur it contains helps neutralize free radicals that are formed as a result of various metabolic process in the body, says Phyllis Balch, author of “Prescription for Nutritional Healing.” If not neutralized, free radicals interact with DNA and the proteins in healthy cells and damage tissues and organs such as skin, nails, heart, liver and lungs.

Lipid Metabolism

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A methionine deficiency affects serum cholesterol levels. In fact, sulfur-containing amino acids such as methionine increase the susceptibility of lipids to peroxidation or degeneration, says Mauro Di Pasquale in “Amino Acids and Proteins for Athletes.” This may play an important role in prevention of plaque formation and heart disease.

Immune System

Methionine also plays an important role in the proper functioning of the immune system. In fact, according to an article in the June 2006 issue of “The Journal of Nutrition,” high methionine levels in the body increase the levels of other amino acids such as glutathione, homocysteine and taurine. But, while glutathione and taurine help improve immune function and suppress inflammatory reactions, increased homocysteine levels may have the opposite effect. Thus it is important for people to talk to their doctor before consuming high amounts of methionine supplements.

Urinary Tract Infections

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According to “The New Anti-Aging Revolution,” methionine may help treat recurrent urinary tract infections by preventing bacteria from adhering to the bladder wall. Experts at the Beth Israel Deaconess Medical Center state that 500 mg of methionine supplements, three days per week, may help treat recurrent bladder infections. However, more research is needed to prove these claims conclusively. Do not take methionine supplements to prevent urinary tract infections without consulting a doctor.


Methionine is the main precursor of the amino acid cysteine, which is in turn converted into glutathione, the main detoxification agent in the body, according to “Prescription for Nutritional Healing.” The authors of “The New Anti-Aging Revolution” say methionine can prevent toxicity caused by pain medications such as acetaminophen. In fact, they note that some experts recommend taking methionine supplements along with acetaminophen.