Influence of vitamin D supplementation on growth, body composition, pubertal development and spirometry in South African schoolchildren: a randomised controlled trial (ViDiKids)

ABSTRACT Objective To determine whether weekly oral vitamin D supplementation influences growth, body composition, pubertal development or spirometric outcomes in South African schoolchildren. Design Phase 3 double-blind randomised placebo-controlled trial ( clinicaltrials.gov registration no. NCT02880982 ). Setting Socio-economically disadvantaged peri-urban district of Cape Town, South Africa Participants 1682 children of Black African ancestry attending government primary schools and aged 6-11 years at baseline. Interventions Oral vitamin D 3 (10,000 IU/week) vs. placebo for 3 years Main outcome measures height-for-age and body mass index-for-age, measured in all participants); Tanner scores for pubertal development, spirometric lung volumes and body composition, measured in a subset of 450 children who additionally took part in a nested sub-study. Results Mean serum 25-hydroxyvitamin D 3 concentration at 3-year follow-up was higher among children randomised to receive vitamin D vs. placebo (104.3 vs. 64.7 nmol/L, respectively; mean difference [MD] 39.7 nmol/L, 95% CI 37.6 to 41.9 nmol/L). No statistically significant differences in height-for-age z-score (adjusted MD [aMD] −0.08, 95% CI −0.19 to 0.03) or body mass index-for-age z-score (aMD −0.04, 95% CI −0.16 to 0.07) were seen between vitamin D vs. placebo groups at follow-up. Among sub-study participants, allocation to vitamin D vs. placebo did not influence pubertal development scores, % predicted forced expiratory volume in 1 second (FEV1), % predicted forced vital capacity (FVC), % predicted FEV1/FVC, fat mass or fat-free mass. Conclusions Weekly oral administration of 10,000 IU vitamin D 3 boosted vitamin D status but did not influence growth, body composition, pubertal development or spirometric outcomes in South African schoolchildren. KEY MESSAGES What is already known on this topic? Observational studies have reported independent associations between vitamin D deficiency in childhood and slower linear growth, reduced lean mass, obesity and precocious puberty. A phase 2 clinical trial conducted in Mongolia reported that a 6-month course of vitamin D supplementation increased height gain in 113 vitamin D deficient schoolchildren aged 12-15 years; however, these results were not confirmed by a recent phase 3 trial conducted in the same setting. RCTs to determine effects of vitamin D supplementation on growth and development in schoolchildren have not been conducted in other settings. What this study adds This placebo-controlled phase 3 clinical trial, conducted in 1682 Black African schoolchildren in Cape Town, South Africa, showed that a 3-year course of weekly vitamin D supplementation was effective in elevating circulating 25-hydroxyvitamin D concentrations. However, this was not associated with any effect on linear growth, body composition, pubertal development or spirometric lung volumes. How this study might affect research, practice or policy Our findings do not support use of vitamin D supplementation as an intervention to influence child growth, body composition, pubertal development or spirometric lung volumes.