L-Methionine Amino Acid Uses & Roles in the Body

L-methionine is an essential amino acid that plays a role in building various protein molecules within the human body. This amino acid cannot be produced within the human body and must be obtained entirely through dietary intake.

Foods that contain significant amounts of this amino acid include fish, meat, seeds and other foods rich in protein. It is also possible to increase your intake of L-methionine by taking a dietary supplement.

The Natural Medicines Database reports that this supplement has been used for many different purposes, ranging from allergies to alcoholism. Bodybuilders commonly take L-Methionine pills to promote muscle gains.

Studies have indicated that this supplement is possibly safe when taken appropriately. However, serious side effects are possible with high doses of L-methionine supplements, so caution is recommended.

Methionine

Amino Acid

Detox

Liver Health

Anti-Aging

How It Works:

• Used to make the anti-oxidant glutathione
• Supports detoxification pathways
• Can be converted into SAMe

Dosage:

25 mg per gram of protein

Safety:

Rated Possibly Safe

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L-Methionine Benefits and Uses

According to the National Center for Biotechnology Information, the amino acid L-methionine serves the following purposes in the human body:

• Support of tissue repair
• Support of growth
• Prevention of excess fat buildup in the liver
• Chelation of toxic heavy metals, including mercury and lead
• Inhibition of cell aging
• Protection of cells from pollutants
• Strengthening of nails, hair and skin

L-methionine is also the precursor for S-Adenosyl methionine (SAM-e), which also plays a number of important roles in the body. SAM-e is involved in the synthesis of neurotransmitters, including dopamine, serotonin and norepinephrine.

The Natural Medicines Database reports that L-methionine has been used medicinally for the following purposes:

• Testing for hyperhomocysteinemia
• Preventing liver damage from acetaminophen poisoning
• Alleviation of radiation side effects
• Copper toxicity
• Asthma
• Parkinson’s disease
• Drug withdrawal
• Schizophrenia
• Allergies
• Alcoholism
• Depression
• Athletic Performance

Research into the effectiveness of L-methionine for each of these purposes is ongoing. Some studies have already shown that L-methionine may be effective for the treatment of acetaminophen poisoning.

However, further research is needed to verify these findings. At this time, there is insufficient evidence to determine whether L-methionine is effective for any of the other ailments on this list.

L-Methionine vs. DL-Methionine

L-methionine and DL-methionine are two isomers of the same amino acid. However, their structures differ slightly.

Research has shown that all of the amino acids within the body’s proteins are of the L-configuration. Thus, the bioavailability of L-methionine and DL-methionine may not be equal.

How Much L-Methionine Should I Take?

The body requires a certain amount of L-methionine in order to function properly. Currently, the dietary reference intake recommendation for cysteine and methionine combined is 25 mg per gram of protein.

However, some or all of this methionine will be derived from food sources. Common dietary sources of this amino acid include eggs, fish, meat, chicken, turkey, brazil nuts, cheese, other dairy products and soybeans.

Higher doses of L-methionine supplements are associated with risks. As a result, consumers are encouraged to exercise caution when using this supplement.

At this time, the United States Food and Drug Administration has not approved L-methionine as a treatment for any ailment or condition. Thus, no standardized dosing guidelines for L-methionine supplements are available.

However, the following dosages have been well tolerated during past clinical trials.

• Parkinson’s disease – 5 grams of methionine daily for two weeks to six months.
• Insomnia – 500 mg of methionine just before bedtime.
• Acetaminophen toxicity – 2.5 grams of methionine at four hour intervals within 10 hours of acetaminophen ingestion.

The Natural Medicines Database reports that dosages of more than 100 mg per kg of body weight should be avoided. Dosages this large may cause severe and potentially fatal cerebral effects.

Some people may experience severe reactions at lower dosages. In order to minimize the risk of adverse effects, begin with a low dosage of L-methionine and gradually increase the amount you take until you have reached the desired level of effectiveness.

Never exceed the dosage recommended by your doctor. Always talk to your doctor before beginning any supplement regimen, including L-methionine. If you experience severe side effects while taking L-methionine, seek immediate medical attention.

L-Methionine Side Effects

Taking L-methionine as a supplement may result in side effects. Some of the most common side effects of methionine supplementation include nausea, vomiting and drowsiness.

According to the National Medicines Database, L-methionine supplementation is considered possibly safe for both adults and children, as long as the supplement is used appropriately.

However, L-methionine may be dangerous if it is used in higher doses. WebMD reports that the following effects may occur if dangerously high doses of L-methionine are consumed:

• Increased blood levels of homocysteine, which may raise the risk of cardiovascular problems
• Increased tumor growth
• Brain damage
• Death

L-methionine Interactions and Contraindications

L-methionine supplements have not been shown to interact with any prescription medications or other supplements. However, it is possible that interactions exist but have not yet been discovered.

Researchers have found that L-methionine will not interact with most foods. However, some studies have shown that a diet containing high levels of nitrite, salt and methionine may raise the risk of gastric cancer.

L-methionine supplementation may also cause problems for people with certain conditions, including schizophrenia, methylenetetrahydrofolate reductase deficiency, liver disease, cirrhosis of the liver, atherosclerosis and acidosis.

If you have any of these conditions, talk to your doctor to find out whether L-methionine supplementation is appropriate for you. L-methionine supplementation is not recommended for pregnant or lactating women.

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