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

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. The objective was to assess whether calcium supplementation increases bone mass gain in prepubertal boys in a skeletal site-specific manner. 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. 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).yr; difference, 12.0 (95% confidence interval, CI, 3.6-20.3), P = 0.006; and 33 +/- 16 vs. 28 +/- 16 mg/cm(2).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).yr; difference, 17.2 (95% CI, 7.9-26.5); n = 174, P < 0.001; and 35 +/- 16 vs. 28 +/- 14 mg/cm(2).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. 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.