Zinc retention and losses of zinc in sweat by preadolescent girls.

Preadolescent girls, ages 7 to 9 years, were fed levels of zinc ranging from 5.61 to 14.61 mg/day during an 18-day metabolic study. All other nutrients were provided at or above Recommended Dietary Allowance levels. The sweat loss of zinc was measured using an arm-bag method and whole body zinc loss was calculated from whole body nitrogen and arm loss of nitrogen and zinc. Fecal zinc reflected dietary zinc, but urinary zinc remained relatively stable. The mean daily loss of zinc through sweat was calculated to be 1.43 mg. Zinc retentions were not significantly different (P greater than 0.05) though the retention increased generally with intake of zinc. A comparison of these data with previously reported studies indicated that the absorption of zinc was usually in the range of 20 to 30%. Based on sweat losses reported by others and found in this study and on usual absorption of zinc, it appears that diets should provide a minimum of 7 mg of zinc daily for growing children.