Bone Abstracts

The relationship between vitamin D status and lean mass accretion in young children is not well understood.

Objective: To explore vitamin D status in relation to lean mass outcomes over 12 mo in children 2–8 years.

Methods: This was a secondary analysis of trial data (clinicaltrials.gov: NCT02097160, NCT02387892) in Montreal, Canada. Children consumed their normal vitamin D intake for 6 mo (Apr–Oct 2014, n=39) and 12 mo (Apr 2014–Apr 2015). Vitamin D status (serum 25(OH)D: Liaison, Diasorin) was measured at all visits (Apr, Oct 2014, Jan, Apr 2015). Standardized anthropometry, skin colour (forehead, forearm and lower leg; spectrophotometer: CM-700d/600d, Konica Minolta), demographics, activity and diet were assessed. Whole body lean and fat mass were measured at baseline, 6 and 12 mo using DXA (Hologic Discovery, APEX v13.3). Spearman correlations, linear regression and a mixed model ANOVA were used.

Results: In Apr 2014, children were 5.1±1.9 years, 54% (21/39) male, with BMI Z-score of 0.72±0.60. Vitamin D intake (222±89 IU/d) did not change across the 12 mo and was not related to 25(OH)D. Serum 25(OH)D increased (P=0.01) from 0 to 6 mo (Apr: 62.0±14.1 nmol/l, Oct: 73.5±13.4 nmol/l). Summer change of skin colour did not correlate with Δ 25(OH)D even though there was significant tanning of skin over summer (individual typological angle 0–6 mo Δ: −12.0±5.5°). Using linear regression, the summer Δ in 25(OH)D was 3.3 nmol/l less for every 10 nmol/l increment in April 25(OH)D (r²=0.60, P=0.01). The summer % change in lean mass positively correlated with Apr 25(OH)D (r=0.37, P=0.02) and was greater in summer than winter (summer: 8.3±3.7, winter: 5.7±3.5 P=0.04). In the subgroup, 25(OH)D decreased (P=0.01) from 6 to 12 mo (Oct: 71.6±15.1 nmol/l, Apr: 61.3±16.3 nmol/l). The 12 mo % Δ in lean mass was higher by 1.5% for every 10 nmol/l increment in Oct 25(OH)D (r²=0.66).

Conclusion: These results suggest 25(OH)D concentration may be an important factor for lean mass accrual in young children. (Clinical trial funding: Dairy Farmers of Canada, Canada Research Chairs and Canada Foundation for Innovation).

Disclosure: The authors declared no competing interests