Health Library

Methionine

Supplement Forms/Alternate Names

  • L-Methionine

Uses

Principal Proposed Uses

  • None

Other Proposed Uses

  • Requirements/Sources
  • Therapeutic Dosages
  • Therapeutic Uses
  • Safety Issues
  • Interactions You Should Know About
  • References

Methionine is an essential amino acid—one of the building blocks of proteins and peptides that your body cannot manufacture from other chemicals. The body uses methionine to manufacture creatine and uses the sulfur in methionine for normal metabolism and growth.

One preliminary study suggests that methionine can prevent bacteria from sticking to urinary tract cells, 1 which may make it useful for preventing bladder infections. ( Cranberry juice is thought to help reduce the incidence of bladder infections in a similar fashion.)

Requirements/Sources

Depending on your body weight, you need 800-1,000 mg of methionine daily for normal health. Deficiency is unlikely because enough methionine is generally available from the diet.

Meat, fish, dairy products, and other high-protein foods are good sources of methionine.

Therapeutic Dosages

A proper therapeutic dosage of methionine has not been determined. One study relating to urinary tract infections used a dosage of 500 mg 3 times daily. A study enrolling people with HIV used a dose of 800 mg 3 times daily.

Therapeutic Uses

Because it seems to discourage bacteria from sticking to the wall of the bladder, methionine has been suggested as a treatment for recurrent bladder infections . 2 However, the evidence that it works is limited to one small trial without a placebo control. (For information on why placebo-controlled trials are essential to prove a treatment effective, see Why Does This Database Depend on Double-Blind Studies? )

One double-blind study found equiviocal evidence that methionine supplements taken at a dose of 2.4 g per day might improve immune function in people with HIV . 8

One study on rats suggests that methionine might protect the liver against the damaging effects of acetaminophen poisoning. 3 On this slim basis, methionine has been proposed as a general liver protectant . However, in this particular study, the action of methionine was more to fight acetaminophen specifically than to protect the liver in general.

Very preliminary evidence suggests methionine might be helpful in treating Parkinson's disease . 4,5 However, this should not be attempted except under physician supervision; see Safety Issues.

Safety Issues

Methionine is thought to be generally safe. However, the maximum safe dosages for young children, pregnant or nursing women, or those with serious liver or kidney disease have not been established.

Like other amino acids, methionine may interfere with the absorption or action of the drug levodopa, which is used for Parkinson's disease . 6

Early studies have shown an exacerbation of psychopathological symptoms in people with schizophrenia. These symptoms did not appear in those without schizophrenia.9

Methionine can increase the levels of homocysteine in your blood. High levels of homocysteine have been linked to certain health conditions particularly cardiovascualr disease. Short term use or moderate doses of methionine have not been linked to cardiovascualr changes. However, excessive intake of methionine may be associated with blood vessel damage and cardiovascular disease. Supplements known to be helpful to the cardiovascular system like folate, vitamin B 6, and vitamin B 12 may be given with methionine to counteract these affects. Talk to your doctor before taking methionine to make sure you are using the correct dose.9

Interactions You Should Know About

If you are taking:

References

1
Funfstuck R, Straube E, Schildbach O, et al. Prevention of reinfection by L-methionine in patients with recurrent urinary tract infection [in German]. Med Klin . 1997;92:574-581.

2
Funfstuck R, Straube E, Schildbach O, et al. Prevention of reinfection by L-methionine in patients with recurrent urinary tract infection [in German]. Med Klin . 1997;92:574-581.

3
Neuvonen PJ, Tokola O, Toivonen ML, et al. Methionine in paracetamol tablets, a tool to reduce paracetamol toxicity. Int J Clin Pharmacol Ther Toxicol . 1985;23:497-500.

4
Smythies JR, Halsey JH. Treatment of Parkinson's disease with L-methionine. South Med J. 1984;77:1577.

5
Meininger V, Flamier A, Phan T, et al. L-methionine treatment of Parkinson's disease: preliminary results [in French]. Rev Neurol (Paris). 1982;138:297-303.

6
Nutt JG, Woodward WR, Hammerstad JP, et al. The "on-off" phenomenon in Parkinson's disease: relation to levodopa absorption and transport. N Engl J Med. 1984;310:483-488.

7
Toborek M, Hennig B. Is methionine an atherogenic amino acid? J Opt Nutr . 1994;3:80-83.

8
Van Brummelen R, du Toit D. L-methionine as immune supportive supplement: a clinical evaluation. Amino Acids . 2006 Sep 29 [Epub ahead of print]

9
Garlick P. Toxicity of methionine in humans. J Nutr. 2006;136(6 suppl):1722S-1725S.

10
Gong Z, Holly EA, Bracci PM. Intake of folate, vitamins B6, B12 and methionine and risk of pancreatic cancer in a large population-based case-control study. Cancer Causes Control. 2009 Oct;20(8):1317-25.