Methionine is an essential amino acid that is required for the absorption, transportation, and bioavailability of zinc and selenium in the body. Methionine also facilitates the breakdown of fats and prevents accumulation of fat in the liver and arteries. Methionine is obtained in the diet from Brewer’s yeast, dairy products, eggs, fish, meat, seafood, and whey.

Methionine appears to prevent bacteria from adhering to the wall of the bladder; this property of methionine has led to it being suggested as a treatment for recurrent urinary tract infections (UTI’s). One trial has found evidence to support this claim, yet the use of methionine in preventing UTI’s has not been confirmed. Methionine has been shown to be effective in the prevention of acetaminophen toxicity, and some experts have suggested selling acetaminophen in combination with the amino acid to prevent acetaminophen poisoning. However, there has been some speculation that chronic use of methionine can increase homocysteine levels.

Methionine deficiency can cause apathy, loss of pigmentation in hair, edema, lethargy, liver damage, muscle loss, fat loss, skin lesions, weakness, and slowed growth in children.

Not established, however one study which used methionine supplements to treat urinary tract infections, found that 500mg taken three times a day had a therapeutic effect.

MAXIMUM SAFE LEVEL: Not established

Some research suggests that methionine may help to relieve some symptoms of Parkinson’s disease. However, several studies have found that S-adenosylmethionine (SAMe) - another form of methionine - worsens symptoms of the disease. Therefore some experts suggest that Parkinson’s disease patients should avoid taking methionine and SAMe at present. Furthermore, methionine may interfere with the absorption or action of the anti-Parkinson’s drug levodopa.

Animal studies suggest that a high intake of methionine, in the presence of B-vitamin deficiencies, may increase the risk of developing atherosclerosis by increasing blood cholesterol and homocysteine levels. People taking supplementary methionine should ensure that they obtain recommended amounts of folate, vitamin B6, and vitamin B12. People with kidney disease or liver disease should consult their doctor before taking methionine.