Methionine
Also known as L-methionine, Met
Methionine is an essential amino acid that the body cannot make, so it must come from food. It starts nearly every protein chain, donates methyl groups for many reactions, and can be used to make cysteine, so the two are measured together as the sulfur amino acids.
Why it matters
What it does in your body
- Protein synthesis and initiation
- Methyl donor for DNA and neurotransmitter reactions
- Precursor to cysteine and glutathione
- Source of sulfur for the body
Intake guidance
How much you need
Methionine is measured together with cysteine as the sulfur amino acids. The IOM sets the combined requirement at 19 mg/kg/day, about 1.3 g/day for a 70 kg adult. Any diet with enough total protein provides plenty.
What affects it
What affects your intake
Total protein intake
Meeting protein needs supplies methionine, which is common in animal foods, eggs, and grains.
Cysteine availability
Because the body makes cysteine from methionine, cysteine in the diet spares some of the methionine requirement.
Plant-based diets
Legumes are relatively low in methionine, so plant-based eaters benefit from including grains, seeds, and soy for balance.
In practice
Good to know
Deficiency is not a realistic concern on a normal mixed diet. Methionine is central to methylation and to making glutathione, the body's main antioxidant. Supplements are rarely needed, and some research is actually exploring methionine restriction for longevity, so more is not necessarily better. A balanced diet supplies the right amount.
Where to get it
Best food sources
The bottom line
A protein-adequate diet covers methionine and cysteine together. There is no general need to supplement it, and extreme intakes are not beneficial.
Track methionine automatically
Methionine is one of the 92 nutrients Vora reads from a photo of your meal, so you can see where you stand without weighing or logging by hand.
Sources and method
The classification, roles, and guidance on this page come from the references below, drawing on the Institute of Medicine (now the National Academies) Dietary Reference Intakes and reputable nutrition science.
- Institute of Medicine (2005), Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids
This page is for general education, not medical advice. Reference intakes are population averages for healthy people and do not replace guidance from your doctor or a registered dietitian, especially if you are pregnant, managing a health condition, or considering supplements.