Whole body bone mineral accretion in healthy children andadolescents

Data on accretion in bone size and bone mineral content (BMC) are needed to evaluate bone mineralisation during childhood. Whole body bone mineral content (BMC) and bone area (BA) were determined by dual energy x ray absorptiometry (Hologic 1000/W) with a one year interval in healthy girls (n = 192) and boys (n = 140) aged 6-19 years. Annual accretion in BMC (ΔBMC (g/year)) and BA (ΔBA (cm²/year)) according to sex and pubertal stages were calculated. ΔBA and ΔBMC were highly significantly associated with pubertal stages in girls and boys. Centile curves for ΔBA and ΔBMC according to sex and age were constructed using the LMS method. Peak ΔBA and ΔBMC values were reached earlier in girls (12.3 and 12.5 years, respectively) than in boys (13.4 and 14.2 years, respectively). The ΔBA peak was dissociated in time from the ΔBMC peak, indicating that increase in bone size occurs before increase in bone mineral content. Assuming that 32.2% of BMC consist of calcium, the median (90th centile) annual bone calcium accretion in pubertal stage III was 220 mg/day (302) and 317 mg/day (386) for girls and boys, respectively. To obtain an average bone calcium accretion, a high calcium absorption is needed during puberty. This may have implications for dietary calcium requirements at this time.