Influence of vitamin D supplementation on muscle strength and exercise capacity in South African schoolchildren: secondary outcomes from a randomised controlled trial (ViDiKids)

Keren Middelkoop, Lisa Micklesfield, Steph Hemmings, Neil Walker, Justine Stewart, David Joliffe, Amy Mendham, Jonathan Tang, Cyrus Cooper, Nicholas C. Harvey, Robert Wilkinson, Adrian R. Martineau

Research output: Contribution to journalArticlepeer-review

Abstract

Objective
To determine whether vitamin D supplementation influences grip strength, explosive leg power, cardiorespiratory fitness and risk of exercise-induced bronchoconstriction (EIB) in South African schoolchildren.

Methods
Substudy (n=450) in Cape Town schoolchildren aged 8–11 years nested within a phase 3 randomised placebo-controlled trial (ViDiKids). The intervention was weekly oral doses of 10 000 IU vitamin D3 (n=228) or placebo (n=222) for 3 years. Outcome measures were serum 25-hydroxyvitamin D3 (25(OH)D3) concentrations, grip strength, standing long jump distance, peak oxygen uptake (VO2peak, determined using 20 m multistage shuttle run tests) and the proportion of children with EIB, measured at end-study.

Results
64.7% of participants had serum 25(OH)D3concentrations <75 nmol/L at baseline. At 3-year follow-up, children randomised to vitamin D versus placebo had higher mean serum 25(OH)D3 concentrations (97.6 vs 58.8 nmol/L, respectively; adjusted mean difference 39.9 nmol/L, 95% CI 36.1 to 43.6). However, this was not associated with end-study differences in grip strength, standing long jump distance, VO2peak or risk of EIB.

Conclusion
A 3-year course of weekly oral supplementation with 10 000 IU vitamin D3 elevated serum 25(OH)D3 concentrations in South African schoolchildren but did not influence muscle strength, exercise capacity or risk of EIB.
Original languageEnglish
Article numbere002019
Number of pages9
JournalBMJ Open Sport & Exercise Medicine
Volume10
Issue number3
DOIs
Publication statusPublished - 26 Sept 2024

Bibliographical note

Publisher Copyright:
© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY. Published by BMJ.

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