From the Guidelines
Methionine supplementation is not recommended for general health purposes due to its potential to increase homocysteine levels and contribute to aging-related diseases, as evidenced by studies showing that restriction of methionine increases lifespan in rodents 1. When considering methionine supplementation, it is crucial to weigh the potential benefits against the risks. Methionine is an essential amino acid that plays a role in various bodily functions, including the production of S-adenosylmethionine (SAMe) and glutathione, which support liver function, joint health, and cellular detoxification processes. However, excessive methionine intake can lead to increased homocysteine levels, which is associated with cardiovascular risks 1.
Some key points to consider regarding methionine supplementation include:
- Restricting methionine intake has been shown to increase lifespan in rodents and reduce vascular aging in rats 1.
- High methionine intake is associated with increased mortality and aging-related diseases in humans, including cardiovascular disease, type 2 diabetes, and cancer 1.
- Vegetable protein sources, which contain less methionine and sulfur-rich amino acids than animal protein, may be a healthier alternative for reducing the risk of aging-related diseases 1.
- Certain individuals, such as those with liver damage or homocystinuria, may require higher therapeutic doses of methionine under medical supervision, but this should be approached with caution due to the potential risks.
In terms of dosage, a typical range for methionine supplementation is 200-500mg daily, taken with meals. However, due to the potential risks associated with excessive methionine intake, supplementation should only be considered under medical supervision and for specific medical conditions. Most healthy individuals can obtain sufficient methionine from protein-rich foods like meat, fish, eggs, and dairy, making supplementation unnecessary unless specifically indicated for a medical condition 1.
From the Research
Effects of Methionine Supplementation
- Methionine supplementation may have both positive and negative effects on health, depending on the dose and individual circumstances 2, 3.
- A high level of methionine intake can lead to adverse effects such as hyperhomocysteinemia, reduced body weight, and increased cholesterol levels 3, 4.
- The no-observed-adverse-effect level (NOAEL) of supplemented methionine is estimated to be 46.3 mg · kg-1 · d-1, and the lowest-observed-adverse-effect level (LOAEL) is estimated to be 91 mg · kg-1 · d-1 in healthy older adults 2, 4.
- Methionine dietary supplementation can potentiate ionizing radiation-induced gastrointestinal syndrome, leading to acute radiation toxicity and alterations in the intestinal microbiome 5.
- High methionine intake can alter gut microbiota and lipid profile, leading to liver steatosis and compromised gut barrier function in mice 6.
Potential Benefits and Risks
- Methionine supplementation may improve hepatic steatosis, insulin resistance, inflammation, fibrosis, and bone health 3.
- However, excessive methionine intake can lead to negative impacts on both the gut and liver, including hepatic steatosis, compromised gut barrier function, and altered gut lipid profile 5, 6.
- The effects of methionine supplementation on cardiovascular disease risk are unclear, but high homocysteine levels (which can be caused by excessive methionine intake) are associated with an increased risk of cardiovascular disease 2, 4.
Dose-Response Relationship
- The dose-response relationship between methionine supplementation and health effects is complex and depends on individual circumstances, such as age, health status, and dietary context 2, 3, 4.
- Further research is needed to establish the optimal dose of methionine supplementation for different populations and health outcomes 2, 3.