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What is methionine? Why do we need it?

Methionine is one of the essential amino acids. It is responsible for supplying sulfur and other elements used by the body for metabolism and growth. Methionine belongs to a collection of compounds called lipotropics, a group that includes choline and inositol.

People with AIDS have been shown to have low methionine levels, which has led some researchers to speculate that some AIDS-related nervous disorders are caused by a lack of methionine. A small study published in 1997 demonstrated that methionine supplements could improve memory in AIDS patients. An early study published in 1984 hinted that methionine may treat some symptoms of Parkinson's disease; however, subsequent studies have shown that another form of methionine, S-adenosylmethionine (or SAMe) may actually worsen Parkinson's symptoms.

How much methionine should I take?

The required amount of amino acids depends on a person's body weight; researchers believe the average adult requires approximately 800-1,000mg of methionine per day. Since this amount is exceeded by most Western diets, it is believed that methionine supplementation is usually not necessary.

What are some good sources of methionine? What forms are available?

Meat, fish and dairy products are all good sources of methionine. Methionine capsules are also available at most health food stores.

What can happen if I don't get enough methionine? What can happen if I take too much? Are there any side-effects I should be aware of?

Low intakes of methionine during pregnancy have been associated with neural tube defects in newborn children. Excessive amounts of methionine in the diet may increase blood cholesterol levels, which could lead to atherosclerosis and cardiovascular disease. This effect appears to be present especially if there is an inadequate intake of folic acid, vitamin B6 and vitamin B12.

At present, there are no known drug interactions with methionine.


  • Cheng H, Gomes-Trolin C, Aquilonius SM, et al. Levels of L-methionine S-adenosyltransferase activity in erythrocytes and concentrations of S-adenosylmethionine and S-adenosylhomocysteine in whole blood of patients with Parkinson's disease. Exp Neurol 1997;145:580—5.
  • Dorfman D, DiRocco A, Simpson D, et al. Oral methionine may improve neuropsychological function in patients with AIDS myelopathy: results of an open-label trial. AIDS 1997;11:1066—7.
  • Shaw GM, Velie EM, Schaffer DM. Is dietary intake of methionine associated with a reduction in risk for neural tube defect-associated pregnancies? Teratology 1997;56:295—9.
  • Tan SV, Guiloff RJ. Hypothesis on the pathogenesis of vacuolar myelopathy, dementia, and peripheral neuropathy in AIDS. J Neurol Neurosurg Psychiat 1998 65:23—8.
  • Toborek M, Hennig B. Is methionine an atherogenic amino acid? J Optimalt Nutr 1994;3(2):80—3.
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