Methionine is one of the essential amino acids (building blocks of protein), meaning that it cannot be produced by the body, and must be provided by the diet. 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, or chemicals that help the liver process fats (lipids). Others in this group include choline, inositol, and betaine (trimethylglycine).
Meat, fish, and dairy are all good sources of methionine. Vegetarians can obtain methionine from whole grains, but beans are a relatively poor source of this amino acid.
Methionine has been used in connection with the following conditions (refer to the individual health concern for complete information):
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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.1
Amino acid requirements vary according to body weight. However, average-size adults require approximately 800–1,000 mg of methionine per day—an amount easily obtained or even exceeded by most Western diets.
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.2 This idea has not yet been tested in humans. Excessive methionine intake, together with 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. Even in the absence of a deficiency of folic acid, B6, or B12, megadoses of methionine (7 grams per day) have been found to cause elevations in blood levels of homocysteine.3 Whether such an increase would create a significant hazard for humans taking supplemental methionine has not been established. Supplementation of up to 2 grams of methionine daily for long periods of time has not been reported to cause any serious side effects.4
At the time of writing, there were no well-known drug interactions with methionine.
1. 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.
2. Toborek M, Hennig B. Is methionine an atherogenic amino acid? J Optimal Nutr 1994;3:80–3.
3. McAuley DF, Hanratty CG, McGurk C, et al. Effect of methionine supplementation on endothelial function, plasma homocysteine, and lipid peroxidation. J Toxicol Clin Toxicol 1999;37:435–40.
4. Leach FN, Braganza JM. Methionine is important in treatment of chronic pancreatitis. Br Med J 1998;316:474 [letter].
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The information presented in Healthnotes is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires September 2008.