Effect of dietary protein and phosphorus levels on the utilization of zinc, copper and manganese by adult males.

Zinc, copper and manganese utilization were examined in eight adult males fed a low protein-moderate phosphorus diet (LPrMP), a low protein-high phosphorus diet (LPrHP), a high protein-moderate phosphorus diet (HPrMP) and a high protein-high phosphorus diet (HPrHP) during a 51-day balance study. The low and high protein diets contained 8.1 g and 24.1 g nitrogen daily, respectively. The moderate and high levels of phosphorus were 1,010 and 2,525 mg phosphorus daily. Subjects lost less zinc in the feces when fed the HPrMP diet than when fed the other three diets. The level of dietary protein and phosphorus all statistically affected fecal zinc excretion. Urinary zinc excretion was significantly greater when subjects consumed the high protein diets rather than the low protein diets. Apparent retention of zinc was greatest when subjects were fed the HPrMP diet rather than the other three diets. This effect was statistically attributable to the interaction between dietary protein and phosphorus. Serum zinc levels were significantly elevated when subjects consumed the high protein rather than the low protein diets. Serum zinc levels were correlated to urinary zinc excretion (r = 0.788, P< 0.001), apparent retention of zinc (r = 0.385, P< 0.05) and serum copper levels (r = 0.395, P < 0.05). Apparent absorption and retention of copper were significantly greater when subjects were fed the high protein rather than the low protein diets. They dietary treatments did not affect the urinary excretion of copper, serum copper levels or the apparent absorption and retention of manganese by these subjects.