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) over bar +/- 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 less than or equal to 0.01); lumbar spine, 1.9 +/- 0.5% (P less than or equal to 0.001); ultradistal radius, 1.3 +/- 0.6% (P less than or equal to 0.05); total hip, 2.7 +/- 0.6% (P less than or equal to 0.001); femoral neck, 2.2 +/- 0.7% (P less than or equal to 0.001); trochanter, 4.8 +/- 0.9% (P less than or equal to 0.001). Attendance at > 50% of the exercise sessions was significant at the total hip (1.4 +/- 0.7%; P less than or equal to 0.05) and trochanter (2.6 +/- 1.2%; P less than or equal to 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.