Skeletal site selectivity in the effects of calcium supplementation on areal bone mineral density gain: A randomized, double-blind, placebo-controlled trial in prepubertal boys

Background: Calcium supplementation during childhood and adolescence is considered an early means of preventing osteoporosis in adults. Prepuberty is an opportune time for detecting the benefits of calcium in girls. Objective: The objective was to assess whether calcium supplementation increases bone mass gain in prepubertal boys in a skeletal site-specific manner. Methods: In a 12-month double-blind, placebo-controlled trial with 1-yr follow-up, 235 healthy prepubertal boys aged 7.4 +/- 0.4 yr ( mean +/- SD) were randomized to receive two food products providing 850 mg/d calcium ( calcium supplement group, n = 116) or an isocaloric placebo ( n = 119). Areal bone mineral density (aBMD) was determined by dual-energy x-ray absorptiometry at radius ( two sites), hip ( two sites), femoral diaphysis (FDia), and L2 - L4 vertebrae. Results: At 12 months, aBMD gain was greater at the FDia and at the mean of the five appendicular skeletal sites in the calcium supplement group in both intention-to-treat analysis [ 76 +/- 32 vs. 64 +/- 33 mg/cm(2) center dot yr; difference, 12.0 (95% confidence interval, CI, 3.6 - 20.3), P = 0.006; and 33 +/- 16 vs. 28 +/- 16 mg/ cm(2) center dot yr; difference, 5.1 ( 95% CI, 0.9 - 9.2); P = 0.018, respectively] and active treatment analysis [ 81 +/- 32 vs. 64 +/- 31 mg/ cm(2) center dot yr; difference, 17.2 ( 95% CI, 7.9 - 26.5); n = 174, P < 0.001; and 35 +/- 16 vs. 28 +/- 14 mg/ cm(2) center dot yr; difference, 7.5 ( 95% CI, 2.9 - 12.2); P = 0.002]. There was no beneficial effect of calcium on lumbar spine. The calcium effect was still detectable by ANOVA repeated measures analysis at the FDia ( P = 0.004) and at the mean of the five appendicular skeletal sites ( P = 0.002) 1 yr after the end of intervention ( active treatment analysis). There was no change in bone size. Conclusion: In prepubertal boys, calcium-enriched foods increased aBMD at several appendicular skeleton sites, but not at the lumbar spine, and this without any bone size change. This effect was maintained 1 yr after treatment discontinuation.