Dietary Protein, DIAAS, Anabolism, and Cardiometabolic Health: A Review and Future Perspectives

The role of dietary protein quality, as defined by the Digestible Indispensable Amino Acid Score (DIAAS) and amino acid composition, in protein kinetics, muscle anabolism, and cardiometabolic health was reviewed, with emphasis on younger and older adults. Protein quality was formerly assessed by the Protein Digestibility-Corrected Amino Acid Score (PDCAAS); however, the DIAAS is more accurate because it accounts for the true ileal digestibility of indispensable amino acids (IAAs). On a gram-for-gram basis, excellent-quality proteins stimulate muscle mass and health outcomes, particularly in the context of age-related anabolic resistance and sarcopenia, but effects on cardiometabolic disease progression are less clear. Exploring the links between DIAAS, whole-body protein net balance (NB), muscle protein synthesis (MPS), and cardiometabolic outcomes could refine dietary strategies to mitigate muscle loss and disease risk. Literature databases were searched for studies on the DIAAS, protein metabolism, and cardiometabolic health. Excellent-quality proteins, compared with lower-quality proteins, improve digestibility and IAA bioavailability, and enhance NB, MPS, and muscle preservation in young and older adults. Some evidence suggests specific amino acid enrichments (eg, cysteine, glycine, arginine, glutamine, glutamate) may improve cardiometabolic health outcomes, whereas enrichments common in higher-quality proteins (eg, leucine, isoleucine, valine, lysine, methionine) may increase cardiometabolic disease risk. Strategically combining protein sources with specific amino acids to improve the DIAAS may also mitigate metabolic and cardiovascular disease risk. Future studies may evaluate DIAAS-driven anabolic and metabolic responses in splanchnic tissues. The DIAAS, as a direct and additive metric of IAA availability, may offer the most accurate assessment of protein-quality effects on anabolism. Considering food protein quality, combinations, and constituent amino acid influences on anabolic and cardiometabolic outcomes could enhance dietary guidelines and interventions.