Effect of Dietary Zinc and Protein Levels on the Utilization of Zinc and Copper by Adult Females

Abstract

Zinc and copper utilization were examined in twenty-three young adult females fed either a moderate protein, low zinc diet, a high protein, low zinc diet, a moderate protein, high zinc diet, or a high protein, high zinc diet during a 24-day metabolic balance study. The moderate and high protein diets contained 7.9 g and 15.2 g nitrogen per day, respectively. The low and high levels of zinc were 9.5 or 10.1 and 18.4 or 19.9 mg daily. Copper intake was constant at approximately 2.0 mg/day. Urinary zinc excretion was significantly greater (P < 0.05) in subjects consuming the high protein diets. Fecal zinc paralleled zinc intake but was not affected by protein intake. Apparent retention of zinc was not significantly different among dietary treatments ranging from -0.29 to 1.58 mg/day. Fecal excretion and apparent retention of copper were not affected by protein intake. Mean copper retentions ranged from 0.12 to 0.30 mg/day. Dietary zinc did not affect copper excretion or retention. Dietary protein, at levels commonly consumed by a substantial portion of the American adult female population, did not affect zinc and copper utilization. Individuals were not consistently in positive balance although average retentions were generally positive.