The essential amino acid present in least amount relative to the requirement for that amino acid. The ratio between the amount of the limiting amino acid in a protein and the requirement provides a chemical index of the nutritional value (see protein quality) of the protein, the chemical score. Most cereal proteins are limited by lysine, and most animal and other vegetable proteins by the sum of methionine + cysteine (see amino acids, sulphur). In whole diets it is usually the sulphur amino acids that are limiting.
Subjects: Medicine and Health.