What does it do? Methionine is one of the essential amino acids (building blocks of protein). It supplies sulfur and other compounds required by the body for normal metabolism and growth. Methionine also belongs to a group of compounds called lipotropics; others in this group include choline, inositol, and betaine.

Persons with AIDS have low levels of methionine. Some researchers suggest that this may explain some aspects of the disease process,^{1 2 3} especially the deterioration that occurs in the nervous system that can cause symptoms including dementia.^{4 5} A preliminary study has suggested that methionine (6 grams per day) may improve memory recall in persons with AIDS-related nervous system degeneration.⁶

Other preliminary studies have suggested that methionine (5 grams per day) may help treat some symptoms of Parkinson’s disease.⁷

Methionine (2 grams per day) in combination with several antioxidants, reduced pain and recurrences of attacks of pancreatitis in a small but well-controlled trial.⁸

Where is it found? Meat, fish, and dairy are all good sources of methionine.

Methionine has been used in connection with the following conditions

Who is likely to be deficient? Most people consume plenty of methionine through a typical diet. Lower intakes during pregnancy have been associated with neural tube defects in newborns, but the significance of this is not yet clear.⁹

How much is usually taken? Amino acid requirements vary according to body weight; however, average-size adults require approximately 500–1,000 mg of methionine per day—an amount exceeded by most Western diets. Therefore, most people would not benefit from methionine supplementation.

Are there any side effects or interactions? Animal studies suggest that diets high in methionine, in the presence of B vitamin deficiencies, may increase the risk for atherosclerosis (hardening of the arteries) by increasing blood levels of cholesterol and a compound called homocysteine.¹⁰ This idea has not yet been tested in humans. Excessive methionine intake, in the presence of inadequate intake of folic acid, vitamin B6, and vitamin B12, can increase the conversion of methionine to homocysteine—a substance linked to heart disease and stroke. However, whether this relationship creates a significant hazard for humans taking supplemental methionine has not been established. Supplementation of up to 2 grams methionine daily for long periods of time has not produced any serious side effects.¹¹

At the time of writing, there were no well-known drug interactions with methionine.

Within Healthnotes Online, information about the effects of a particular supplement or herb on a particular condition has been qualified in terms of the methodology or source of supporting data (for example: clinical, double blind, meta-analysis, or traditional use). For the convenience of the reader, the information in the table listing the supplements for particular conditions is also categorized. The criteria for the categorizations are: “Primary” indicates there are reliable and relatively consistent scientific data showing a health benefit. “Secondary” indicates there are conflicting, insufficient, or only preliminary studies suggesting a health benefit or that the health benefit is minimal. “Other” indicates that an herb is primarily supported by traditional use or that the herb or supplement has little scientific support and/or minimal proven health benefit.

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References:

1. Muller F et al. Elevated plasma concentration of reduced homocysteine in patients with Human Immunodeficiency Virus infection. Am J Clin Nutr 1996;242–46.
2. Revillard JP. Lipid peroxidation in Human Immunodeficiency Virus infection. J Acquired Immunodef Synd 1992;5:637–38.
3. Singer P et al. Nutritional aspects of the Acquired Immunodeficiency Syndrome. Am J Gastroenterol 1992;87:265–73.
4. Tan SV, Guiloff RJ. Hypothesis on the pathogenesis of vacuolar myelopathy, dementia, and peripheral neuropathy in AIDS. J Neurol Neurosurg Psychiat 1998 65:23–28.
5. Keating JN et al. Evidence of brain methyltransferase inhibition and early brain involvement in HIV-positive patients. Lancet 1991;337:935–39.
6. 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;11:1066–67.
7. Smythies JR, Halsey JH. Treatment of Parkinson’s disease with l-methionine. South Med J 1984;77:1577.
8. Uden S, Bilton D, Nathan L, et al. Antioxidant therapy for recurrent pancreatitis: placebo-controlled trial. Aliment Pharmacol Ther 1990;4:357–71.
9. 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;56:295–99.
10. Toborek M, Hennig B. Is methionine an atherogenic amino acid? J Optimalt Nutr 1994;3(2):80–83.
11. Leach FN, Braganza JM. Methionine is important in treatment of chronic pancreatitis. Br Med J 1998;316:474 [letter].