Methionine + Cysteine

What it builds

Methionine has a job no other amino acid has: it starts every new protein chain your body builds. It is literally the first amino acid in translation. Cysteine can be manufactured from methionine, which is why WHO tracks the two as a single pool rather than two lines, and why AminoLens does the same.

Beyond construction, the pair is your body's sulphur delivery service. That sulphur goes into glutathione, the master antioxidant your cells run on, into keratin for hair, nails and skin, and into the methylation reactions that regulate a large slice of your biochemistry.

Where methionine + cysteine actually comes from

Eggs are the standout. Among plants the answer is seeds and grains rather than legumes: sesame, sunflower, oats.

Ranked by a realistic portion rather than per 100 g, because nobody eats 100 g of pumpkin seeds. Figures are digestibility-adjusted, so these are the amounts the app credits you with, not the amounts printed on the packet. Computed live from the 72 foods in the AminoLens recommender pool.

Signs you might be short

This is the mirror image of lysine, and it catches the opposite person. A diet heavy on beans, lentils and chickpeas with little grain or seed runs short on sulphur amino acids rather than on lysine.

Brittle hair and nails are the folkloric sign, and we are not going to pretend that is a diagnostic. In practice you will see it as a short red line in your Sankey long before you would notice it anywhere else.

Pairs well with

Grains and seeds. Beans and rice covers it from the other direction. So does hummus, which is chickpeas (lysine-rich, sulphur-poor) plus sesame tahini (sulphur-rich, lysine-poor): a complete pairing that happens to be a single dip, invented long before anyone could have known why it works.