Protein requirements of adults from an evolutionary perspective.

It is argued that the observed minimum needs for protein and individual amino acids by adult humans and animals may merely reflect the diet that their predecessors consumed in the course of their evolution. The ability to adapt to diets with a lower proportion of protein than was ever encountered in practice would have given no competitive advantage. This can explain the limited ability to reduce rates of amino acid catabolism. The protein requirement of domestic cats, obligate carnivores, corresponds to approximately 20% of their energy requirement. Humans adapt to lower levels (approximately 6%). Some urge that higher protein intakes, resulting in higher rates of protein synthesis and turnover, are desirable and that, in general, the more prosperous and successful groups eat more protein. But cause and effect may be reversed. Are higher rates of turnover and catabolism necessarily beneficial? Objective data are still not available.