L-Methionine: Benefits, Dosage and Safety

What is L-Methionine?

L-Methionine is an essential sulphur-containing amino acid that is critical for many cellular functions, including protein synthesis and cellular metabolism. Studies have shown that methionine deficiency can cause a variety of diseases in humans, such as anaemia, grey hair, fatty liver, muscle degeneration, difficulty in healing wounds, oedema and skin lesions. Severe methionine deficiency may also lead to dementia. L-Methionine can be obtained from the daily diet (e.g., meat, eggs, salmon, soybeans and walnuts) or through the use of L-Methionine supplements to maintain the body's health status.

Benefits

Reducing Hepatotoxicity

The oral dietary supplement S-adenosyl-L-methionine (SAMe) has been shown to normalise liver function in patients with a variety of chronic liver diseases, including alcoholic and non-alcoholic cirrhosis, oestrogen-induced cholestasis and other forms of cholestasis, and to prevent or reverse hepatotoxicity induced by medications and chemicals such as alcohol, paracetamol (acetaminophen), steroids and lead, among others.

Antidepressant effects

L-Methionine supplementation was superior to placebo in the treatment of depressive disorders and had approximately the same efficacy as standard tricyclic antidepressants. It is also well tolerated, with most adverse effects manifesting as mild to moderate gastrointestinal distress. However, there is also an apparent possibility that this drug may cause more serious psychiatric and cardiovascular adverse effects. Clinical efficacy remains controversial and more robust studies are needed to support these claims.

Anticancer effects

Several studies have shown that L-methionine has anti-cancer properties. It may be effective against breast, pancreatic, Glioblastoma and liver cancer cells. L-methionine has been reported to be an essential part of the growth cycle of some types of cancer cells and limiting L-methionine intake may inhibit cancer cell growth.

Extended life

Studies have shown that limiting dietary methionine intake to 80 per cent slows the progression of age-related diseases and extends lifespan in rodents. A recent study in 2023 found that limiting methionine intake also improved cognitive function in mice. However, there is currently a lack of clinical data to support these benefits.

Contributes to sleep

Research has shown that three AIDS patients suffering from chronic insomnia experienced a dramatic improvement in their ability to sleep after taking 500mg of the amino acid L-methionine. The results reported were similar to those seen with the prescription drug naltrexone.

Other benefits

antioxidant

Reducing bacterial growth

Prevents kidney stone formation

Nourishes hair, skin and nails

Dosage

There is no standardised dose of L-methionine. The recommended dose for adults is 15 mg/kg body weight per day. For children, the recommended dose is 39 mg/kg body weight per day. It should be used according to your doctor's advice. According to information from the Norwegian Food Safety Authority (NFSA), L-methionine is an ingredient in food supplements sold in Norway. NFSA has requested a risk assessment of the intake of 200, 300, 500, 600 and 700 mg L-methionine per day from food supplements. The total L-methionine exposure from other sources than food supplements is not included in the risk assessment. VKM concludes that: VKM maintains the guidance level from 2013 at 210 mg methione per day.

Safety

L-Methionine is well tolerated at regular doses, and mildly common side effects include nausea, vomiting, drowsiness, excitability, dizziness, and low blood pressure. Taken incorrectly, it can produce serious side effects such as high cholesterol levels, which can increase the risk of cardiovascular disease, heart attack, and stroke. Overdose may also lead to L-methionine toxicity (which causes neurotoxic effects in the body) and an increased risk of type 2 diabetes, heart disease, certain types of cancer, brain changes such as schizophrenia, and memory disorders.

References:

[1] CW FETROW  J. R A. Efficacy of the Dietary Supplement S-Adenosyl-L-Methionine[J]. Annals of Pharmacotherapy, 2001. DOI:10.1345/aph.1Z443.

[2] CARMEN E. PERRONE. Metabolic adaptations to methionine restriction that benefit health and lifespan in rodents[J]. Experimental gerontology, 2013. DOI:10.1016/j.exger.2012.07.005.

[3] MARK L SOWERS; Lawrence C S. Glioblastoma and Methionine Addiction.[J]. International Journal of Molecular Sciences, 2022. DOI:10.3390/ijms23137156.

[4] M. DE VANNA  R. R. Oral S-adenosyl-L-methionine in depression[J]. Current Therapeutic Research-clinical and Experimental, 1992, 52 3: Pages 478-485. DOI:10.1016/S0011-393X(05)80424-2.