Bone Abstracts

We have previously shown a high prevalence of vitamin D inadequacy (serum 25-hydroxyvitamin D (S25(OH)D) <50 nmol/l) in adolescents (14–18 years) in the UK (51°N)⁽¹⁾. It is well recognised that vitamin D deficiency (S25(OH)D <25 nmol/l) increases the risk of rickets and impaired growth in adolescents, however the optimal vitamin D status for bone health is debated. The aim of this study was to investigate the effects of vitamin D status on bone health parameters in white male and female adolescents aged 14–18 years. A total of 110 adolescents (mean age 15.9±1.4 years; 43% male) were recruited onto a vitamin D dose-response randomised controlled trial. At baseline, anthropometric and dietary information was collected, S25(OH)D was measured and bone geometry of the non-dominant radius was assessed by peripheral quantitative computed tomography (pQCT). Mean S25(OH)D concentration was 49.1±12.3 nmol/l. When S25(OH)D concentrations were stratified by tertile, adolescents in the lowest tertile (≤44.7 nmol/l) had lower trabecular volumetric bone mineral density (vBMD) than those in the highest tertile (≥52.4 nmol/l) (P=0.012). These differences persisted after controlling for sex, age, Tanner stage, height, weight and calcium intakes (ANCOVA P=0.003). Trabecular vBMD z-score, calculated using published reference data for UK white children and adolescents⁽²⁾, was lower in the lowest vs the highest tertile of S25(OH)D (0.30±1.22 and 0.90±0.88 respectively; P=0.050). There were no differences in other pQCT measured bone parameters across the S25(OH)D tertiles. In conclusion, while debate regarding the optimal vitamin D status for bone health continues, this study has shown that adolescents with higher S25(OH)D concentrations (>53 nmol/l) had greater trabecular vBMD than those with lower concentrations. However it is not known whether this association arises due to lower bone remodelling and this requires further investigation. If maintaining a circulating 25(OH)D concentration above 50 nmol/l is confirmed to be beneficial for bone accretion in adolescents, we have shown that dietary vitamin D intakes of 30 μg/day would be required to achieve this⁽¹⁾. This study was funded by the European Community’s Seventh Framework Programme, Grant Agreement 613977 for the ODIN Project.

Disclosure: The authors declared no competing interests.

Reference
1. Smith et al. 2016 Am J Clin Nutr, 104, 1301–1309.

2. Ashby et al. 2009 Osteoporos Int, 20, 1337–1346.