Bone Abstracts

In children, it is not well understood how bone mineral accretion is related to lean mass accretion and vitamin D status.

Objective: To explore over 12 mo how bone parameters relate to lean mass and vitamin D metabolites in children 2–8 years.

Methods: This was a secondary analysis of data from 2 trials (clinicaltrials.gov: NCT02097160, NCT02387892) in Montreal, Canada. Children consumed their normal diet without vitamin D supplements for 12 mo starting in Apr 2014 (n=21) with 4 study visits (Apr and Oct 2014, Jan and Apr 2015). At all 4 time-points, vitamin D status (total serum 25(OH)D: Liaison, Diasorin) was assessed. At 6, 9 and 12 mo, bone biomarkers were measured (Liaison, Diasorin, IDS iSYS) followed by standardized anthropometry, demographics, activity and dietary questionnaires. Bone mineral content (BMC) and body composition were measured at baseline, 6 and 12 mo and using dual-energy x-ray absorptiometry (Hologic Discovery, APEX v13.3). Statistical analyses included linear regression and mixed model ANOVA.

Results: In Apr 2014, children were 5.0±1.9 y, 52% (11/21) male, with BMI Z-score of 0.79±0.90. Calcium and vitamin D intake were 1097±396 mg/d and 229±120 IU/d, 80% (16/20) of children maintained serum 25(OH)D ≥ 50 nmol/l over the 12 mo and 95% (20/21) of children were physically activity (60 min/d). Height velocity was not different between summer and winter (0–6 mo: 0.61±0.09 cm/mo, 6–12 mo: 0.57±0.13 cm/mo). The % change in whole body BMC increased (P<0.01) during winter (0–6 mo: 0.4±3.4%, 6–12 mo: 6.5±2.8%). Bone formation biomarkers P1NP and osteocalcin increased from 6 to 12 mo (P< 0.05) whilst bone resorption marker CTx, and PTH did not change. Using linear regression, for every 5% increment in summer change in lean mass, there was a 1.5% higher winter lumbar spine bone mineral accretion (r²=0.70) and a 1.0% higher winter whole body BMC % change (r²=0.66, P<0.05). Twelve month changes in 25(OH)D were relatively homogenous, which may explain why 25(OH)D did not explain changes in BMC.

Conclusion: Winter bone mineral accretion in children 2–8 years may be positively and temporally related to lean mass accretion in the preceding seasons. (Clinical trial funding: Dairy Farmers of Canada, Canada Research Chairs and Canada Foundation for Innovation).

Disclosure: The authors declared no competing interests.