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).
Methionine has been used
in connection with the following conditions (refer to the individual
health concern for complete information):
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.1
How much is usually taken?
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.
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.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.
References: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].