Topic overview

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A protein’s quality depends on its supply of indispensable amino acids and the body’s ability to digest and use them. Complete proteins provide all essential amino acids in adequate amounts; incomplete proteins lack one or more. The amino acid in shortest supply relative to need is the limiting amino acid, and complementary foods such as cereals with legumes can help offset differences in their amino acid profiles. Quality measures—including BV, NPU, PDCAAS, DIAAS, PER, and chemical score—assess protein use in different ways. Digestibility and processing can affect these assessments: cooking may improve digestibility, while factors such as inhibitors, phytates, tannins, and Maillard reactions may reduce protein quality. The full lesson also connects protein quality with requirements and related mechanisms.