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

Abstract

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/cm2·yr; difference, 12.0 (95% confidence interval, CI, 3.6 -20.3), P = 0.006; and 33 ± 16 vs. 28 ± 16 mg/cm2·yr; difference, 5.1 (95% CI, 0.9 -9.2); P = 0.018, respectively] and active treatment analysis [81 32 vs. 64 ± 31 mg/cm2·yr; difference, 17.2 (95% CI, 7.9 -26.5); n = 174, P < 0.001; and 35 ± 16 vs. 28 ± 14 mg/cm2·yr; difference, 7.5 (95% CI, 2.9 -12.2); P = 0.002]. There was no beneficial effect of calcium 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 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. Copyright © 2005 by The Endocrine Society.