Introduction
Dietary protein is essential to human health and it is the primary
source of amino acids, the structural components of all body
proteins. Inadequate dietary protein intake may result in a negative
nitrogen balance and, ultimately, loss of skeletal muscle mass
(Calloway 1975), as endogenous proteins are rapidly degraded to
provide amino acid precursors to sustain protein turnover and energy
metabolism (Stein and others 1991). To prevent muscle loss,
the Inst. of Medicine (IOM) has established a recommended dietary
allowance (RDA) for protein (0.8 g protein·kg−1·d−1). The
RDA for protein is considered the level of high-quality protein
required for nearly 98% of healthy American adults to maintain
nitrogen balance (National Academy of Sciences 2005). Protein
recommendations for Americans are similar to international dietary
protein recommendations (0.83 g protein·kg−1·d−1) estab