Complete vs Incomplete

Protein is built from amino acids, and your body uses 20. Nine are essential, meaning food is the only source.

• Animal proteins (meat, fish, eggs, dairy) carry all nine in good amounts. These are complete proteins
• Most single plant foods run short on one or two: grains lack lysine, beans lack methionine
• Eat a mix of plants across the day and the gaps fill in on their own

The old rule that vegetarians must pair proteins at every meal was retired long ago. Your body keeps a running pool of amino acids from everything you eat.