Bone Abstracts

In rural Gambian prepubertal children with low calcium intakes (mean 300 mg/day) we reported positive effects, sustained for at least a year (y), on bone mineral content (BMC) after 12 months supplementation with calcium carbonate to international levels^1,2. The group was followed up regularly until the end of height growth, and supplementation did not affect height growth in the girls³. Our aim was to determine whether the supplementation altered the timing of skeletal growth and mineral accretion, based on the age at peak velocity (APV).

The trial involved 80 girls (8.0–11.9y) randomised to Ca (1000 mg/day, 5-days/week for 1y) or placebo (P), and followed up for 13y. DXA scans and anthropometry were performed 1y and 2y post-supplement and biennially until age 19 when measurements were taken at 1–2y intervals. Outcomes were whole body (WB) and lumbar spine (LS) BMC and bone area (BA), and lean mass. Within-individual changes over time and the effects of supplementation on the longitudinal profiles were analysed by the Superimposition by Translation and Rotation method⁴. Results for APV are presented as mean difference (SEM) (months(mo)).

For the whole group mean APV was: lean mass 13.6y, WBBA 13.8y, LSBA 13.9y, LSBMC 14.4y, WBBMC 14.7y. Comparing the Ca and P groups, APV was earlier at all sites in the Ca group, but not significantly so (WBBMC 0.9 (0.4) mo; WBBA 0.4 (3.6) mo; LSBMC 0.6 (2.4) mo; LSBA 0.7 (2.2) mo).

A year of pre-pubertal Ca supplementation in Gambian girls accustomed to a low calcium intake had no sustained effects on the timing of skeletal growth and mineral accretion. These results mirror those for height growth,³ and are in contrast to our findings in boys where mean APV in the Ca group was significantly earlier than in the P group⁵. The mechanisms underlying this apparent sexual dimorphism in response to supplementation require further study.

1. Dibba et al. Am J Clin Nutr 2000 71

2. Dibba et al. Am J Clin Nutr 2002 76

3. Prentice et al. Am J Clin Nutr 2012 96

4. Cole et al. Int J Epidemiol 2010 39

5. Ward et al. J Clin Endocrinol Metab 2014 99(9)

Disclosure: The authors declared no competing interests.