Effect of a calcium and exercise intervention on the bone mineral status of 16–18-y-old adolescent girls

Background: Osteoporosis may be prevented or delayed by maximizing peak bone mass through diet modification and physical activity during adolescence. Objective: We studied whether increases in calcium intake and physical activity effectively increase the bone mineral status of adolescent girls aged 16‐18 y. Design: We conducted a 15.5-mo study of calcium supplementation (1000 mg Ca/d as carbonate) in 144 adolescent girls aged 17.3 ± 0.3 y (x ± SD). The subjects were randomly allocated to an exercise (three 45-min exercise-to-music classes/wk during term time) or nonexercise group. Dual-energy X-ray absorptiometry of the whole body, spine, forearm, and hip was performed before and after intervention. Results: The mean (± SD) percentage of subjects compliant with supplement taking was 70 ± 27% and with exercise class attendance was 36 ± 25%. Baseline calcium intake was 938 ± 411 mg/d. Calcium supplementation significantly increased size-adjusted bone mineral content. The effect was stronger in subjects with good compliance (percentage difference ± SE): whole body, 0.8 ± 0.3% (P ≤ 0.01); lumbar spine, 1.9 ± 0.5% (P ≤ 0.001); ultradistal radius, 1.3 ± 0.6% (P ≤ 0.05); total hip, 2.7 ± 0.6% (P ≤ 0.001); femoral neck, 2.2 ± 0.7% (P ≤ 0.001); trochanter, 4.8 ± 0.9% (P ≤ 0.001). Attendance at > 50% of the exercise sessions was significant at the total hip (1.4 ± 0.7%; P ≤ 0.05) and trochanter (2.6 ± 1.2%; P ≤ 0.05). Conclusions: Calcium supplementation and exercise enhanced bone mineral status in adolescent girls. Whether this is a lasting benefit, leading to the optimization of peak bone mass and a reduction in fracture risk, needs to be determined. Am J Clin Nutr 2003;77:985‐92.