Zinc balance in adolescent females consuming a low- or high-calcium diet

Abstract

There is increasing evidence that calcium intake up to the threshold amount (1480 mg/d) increases bone mass during growth. However, there is concern that such a high calcium intake may interfere with the utilization of other nutrients such as zinc, which is also important for skeletal development. The purpose of our study was to investigate the effect of long- term calcium supplementation on zinc utilization in 26 adolescent females (x̄ ± SD age 11.3 ± 0.5 y) during a 14-d period. Each day subjects consumed a metabolic diet containing 722 mg Ca and 6.3 mg Zn. Participants were randomly assigned to receive either a placebo or a calcium supplement containing 1000 mg supplemental Ca/d as calcium citrate malate. Supplementation began 15 wk before the balance period to allow for adaptation to the greater calcium intake. Mean (± SD) zinc balance (0.8 ± 0.8 compared with 0.3 ± 1.1 mg/d, P = 0.23), fecal zinc (4.3 ± 0.6 compared with 4.7 ± 1,4 mg/d, P = 0.27), urinary zinc (0.4 ± 0.2 compared with 0.5 ± 0.1 mg/d, P = 0.55), and net zinc absorption (21% compared with 15%, P = 0.33) were not significantly different between the high- and low-calcium groups. Our results suggest that increasing the recommended dietary allowance of calcium to 1500 mg/d as recommended by the National Institutes of Health consensus panel will not have adverse effects on zinc utilization in adolescent females.