Methionine

Related Terms

Amino acid, butanoic acid, C5H11NO2S, D-methionine, essential amino acid, L-methionine, M, Met, metioniini (Finnish), methionin (Czech, Danish), Methionin (German), metionin (Czech, Danish, Faroese, Norwegian, Swedish), metion?n (Slovenian), metionina (Hungarian, Italian, Polish, Portuguese, Spanish), m?thionine (French), nonpolar amino acid, S-adensyl-L- methionine (SAMe).

Background

Methionine is one of nine essential amino acids, so called because they cannot be made by the human body and must be obtained through the diet. Sources of methionine include protein-rich foods such as beef, chicken, fish, liver, pork, cottage cheese, eggs, lentils, pumpkin seeds, sesame seeds, sunflower seeds, and yogurt.
Supplementary L-methionine has been used to treat symptoms of Parkinson's disease, insomnia, and severe acetaminophen (e.g., Tylenol?) poisoning. In addition, increased dietary intake of methionine has been shown to reduce the risk of a specific type of brain and spinal cord birth defect known as neural tube defects (NTDs). More well-designed human studies are needed to determine if methionine is safe and effective for treating any medical condition.
Very high doses of supplementary methionine have been shown to increase levels of the amino acid homocysteine. High homocysteine levels are a risk factor for heart disease. Some studies have suggested links between methionine and cancer, but more research is needed before firm conclusions can be made.

Evidence Table

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. GRADE *
These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. GRADE *


Several studies have investigated the use of methionine for treatment of acetaminophen (e.g., Tylenol?) overdose. In a study of patients with acetaminophen poisoning, methionine worked as well as standard treatment with acetylcysteine in preventing major liver damage and death. Further study is required before any conclusion can be made.

 C


Several studies have investigated the use of methionine for treatment of acetaminophen (e.g., Tylenol?) overdose. In a study of patients with acetaminophen poisoning, methionine worked as well as standard treatment with acetylcysteine in preventing major liver damage and death. Further study is required before any conclusion can be made.

 C


A small, preliminary human study showed that L-methionine may help relieve chronic insomnia in AIDS patients. Additional research on methionine as a therapy for insomnia is needed.

 C


A small, preliminary human study showed that L-methionine may help relieve chronic insomnia in AIDS patients. Additional research on methionine as a therapy for insomnia is needed.

 C


Results of a human study revealed a lower risk of neural tube defects (birth defects of the brain and spinal cord) in the fetuses of women who had relatively higher dietary intake of methionine near the time that they became pregnant. Additional research is needed to investigate the roles of dietary and supplemental methionine in reducing this type of birth defect.

 C


Results of a human study revealed a lower risk of neural tube defects (birth defects of the brain and spinal cord) in the fetuses of women who had relatively higher dietary intake of methionine near the time that they became pregnant. Additional research is needed to investigate the roles of dietary and supplemental methionine in reducing this type of birth defect.

 C


Supplementary methionine helped reduce some clinical symptoms of Parkinson's disease in a small human study. More high quality studies are needed to clearly determine the effectiveness of methionine in the treatment of Parkinson's symptoms.

C


Supplementary methionine helped reduce some clinical symptoms of Parkinson's disease in a small human study. More high quality studies are needed to clearly determine the effectiveness of methionine in the treatment of Parkinson's symptoms.

C
* Key to grades

A: Strong scientific evidence for this use
B: Good scientific evidence for this use
C: Unclear scientific evidence for this use
D: Fair scientific evidence for this use (it may not work)
F: Strong scientific evidence against this use (it likley does not work)
* Key to grades

A: Strong scientific evidence for this use
B: Good scientific evidence for this use
C: Unclear scientific evidence for this use
D: Fair scientific evidence for this use (it may not work)
F: Strong scientific evidence against this use (it likley does not work)

Tradition / Theory

The below uses are based on tradition, scientific theories, or limited research. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. There may be other proposed uses that are not listed below.

Dosing

Adults (18 years and older)
The dietary reference intake recommendation for methionine and cysteine combined is 25 milligrams per gram of protein.
For acetaminophen (e.g., Tylenol?) toxicity, 2.5 grams of methionine has been taken by mouth every four hours for four doses with good results when given within 10 hours after acetaminophen use.
For insomnia, 500 milligrams of methionine has been taken by mouth just before bedtime.
For Parkinson's disease, 5 grams of methionine has been taken by mouth daily for two weeks to six months.

Safety

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Interactions

Interactions with Drugs
Methionine may interact with anticancer agents (including cisplatin and 5-fluorouracil), agents that elevate homocysteine levels (including fenofibrate, niacin, metformin, antiseizure drugs, levodopa, and methotrexate), and agents that may damage the liver.

Attribution

This information is based on a systematic review of scientific literature edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

Bibliography

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