Muscle plays a central role in whole-body protein metabolism by
serving as the principal reservoir for amino acids to maintain protein
synthesis in vital tissues and organs in the absence of amino acid
absorption from the gut and by providing hepatic gluconeogenic
precursors. Furthermore, altered muscle metabolism plays a key role
in the genesis, and therefore the prevention, of many common pathologic
conditions and chronic diseases. Nonetheless, the maintenance
of adequate muscle mass, strength, and metabolic function has
rarely, if ever, been targeted as a relevant endpoint of recommendations
for dietary intake. It is therefore imperative that factors directly
related to muscle mass, strength, and metabolic function be included
in future studies designed to demonstrate optimal lifestyle behaviors
throughout the life span, including physical activity and diet