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Amino Acids
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Other name(s):

a-amino-g-methylthiol-n-butyric acid


Methionine is an amino acid which is required in protein synthesis as well as synthesis of a number of additional physiologic compounds.  

Unsubstantiated claims

Please note that this section reports on claims that have NOT yet been substantiated through scientific studies.

Methionine is an antioxidant and is thought to help protect the body from damage caused by ionizing radiation, detoxify harmful substances in the body (particularly heavy metals), and inhibit fat deposition in the liver.

In addition, methionine may help alleviate fatigue and may be useful in lessening early balding and the effects of osteoporosis.

Recommended intake

Amino acids (AAs) are available as individual AAs or in proprietary AA combinations, as well as part of multi-vitamin formulas, proteins, and food supplements. The forms include tablets, fluids, and powders. However, adequate protein in the diet should provide a sufficient source of all amino acids.

There are no conditions that increase the nutritional requirements for methionine.

Side effects, toxicity, and interactions

The use of a single amino acid supplement may lead to a negative nitrogen balance, decreasing metabolic efficiency and increasing the workload in the kidneys. In children, taking single amino acid supplements may also harmfully affect growth parameters.

Always avoid taking individual amino acids in high dosage for prolonged periods.

Women who are pregnant or breastfeeding should not use methionine supplements.

Toxicity of methionine is rare (primarily observed only in excessive dosages). 

Individuals with homocystinuria type I, an inherited disease, should not use methionine supplements.

Supplementation without sufficient intake of folic acid, vitamin B6, and vitamin B12 can increase the conversion of methionine to homocysteine. This may increase risk for cardiovascular disease.  

Additional information

Click here for a list of reputable websites with general information on nutrition.

Online Medical Reviewer: Wilkins, Joanna, R.D., C.D.
Date Last Reviewed: 1/21/2013
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