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

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.

Setting: Socioeconomically 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 (10 000 IU/week) versus 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 substudy.

Results: Mean serum 25-hydroxyvitamin D concentration at 3-year follow-up was higher among children randomised to receive vitamin D versus 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 versus placebo groups at follow-up. Among substudy participants, allocation to vitamin D versus placebo did not influence pubertal development scores, % predicted forced expiratory volume in 1 s (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 boosted vitamin D status but did not influence growth, body composition, pubertal development or spirometric outcomes in South African schoolchildren.

Trial Registration Numbers: ClinicalTrials.gov NCT02880982, South African National Clinical Trials Register DOH-27-0916-5527.