Plant vs. Animal Protein: Comparative Biological Analysis of Digestibility, Amino Acid Profile, and Metabolic Effects

Abstract

The global shift toward sustainable diets has reignited discussion on the biological adequacy of plant-derived versus animal-derived proteins. This narrative review synthesizes current evidence on true ileal digestibility, indispensable amino-acid profiles, and metabolic outcomes associated with each protein source throughout the life span. Recent studies show that most animal proteins achieve DIAAS values ≥ 90 %, whereas common plant proteins range from 45 % to 75 %, with notable exceptions such as soy and potato approaching 80 % when properly processed. Disparities stem from intrinsic amino-acid composition and the presence of antinutritional factors that limit plant protein accessibility. Functionally, lower leucine density in cereals and legumes requires larger portions or complementary protein combinations to maximize muscle protein synthesis, particularly in older adults with anabolic resistance. Concurrently, plant-centered dietary patterns are linked to improved lipid profiles, better glycaemic control, and reduced cardiovascular risk, whereas high intakes of processed meats correlate with low-grade inflammation and excess adiposity. We conclude that mixed or strategically complemented plant-based diets can reconcile protein quality, cardiometabolic health, and environmental sustainability, provided that adequate food processing and blending techniques are employed.