Zinc, Nitrogen, Copper, Iron, and Manganese Balance in Adolescent Females Fed Two Levels of Zinc

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Abstract
The effect of feeding two different levels of zinc (Diet Z11.5 and Diet Z14.7) on zinc, nitrogen, copper, iron, and manganese balances was determined in 11 girls, 12.5 to 14.2 years, during a 30-day period. Diet Z11.5 provided 11.32 or 11.64 mg zinc daily, levels similar to that determined previously to be consumed by average adolescent females. Diet Z14.7 provided 14.52 or 14.84 mg zinc daily. These levels were just slightly less than the Recommended Dietary Allowance for zinc. When fed Diet Z14.7, subjects lost significantly more zinc in their feces than when fed Diet Z11.5. Regression analyses were applied to the zinc balance data from this study and a previous study with adolescent females. By extrapolation, a dietary intake of 11 mg zinc daily was estimated to compensate for fecal and urinary zinc losses of the average girl in these studies. The standard error of the estimate was 2.18 mg zinc daily. Nitrogen excretion and retention were unaffected by the variations in zinc intake. Copper excretion in the feces was significantly increased when subjects were fed Diet Z14.7 rather than Diet Z11.5. Manganese and iron fecal losses were also significantly correlated to zinc fecal losses.