Whole body surface loss of trace metals in normal males.

Whole body surface losses of zinc, copper, and iron were measured in 13 male volunteers who lived in a controlled environment for 4 to 9 months. For 88 daily samples, the mean losses for zinc, copper, and iron were 0.50, 0.34, and 0.33 mg/day (3.9, 26, and 2.1% of the mean dietary intakes, respectively). There was a large variance in metal losses with no significant differences in variance within-versus-between subjects or on the same-versus-different diets. The surface losses of zinc and iron increased the apparent dietary requirements determined by balance measurements only 5 and 3%, respectively, while the increase in copper requirement due to surface loss was 25 to 30%.