Influence of vitamin D supplementation on muscle strength and exercise capacity in Mongolian schoolchildren: secondary outcomes from a randomised controlled trial

Davaasambuu Ganmaa, Steph Hemmings, David Joliffe, Uyanga Buyanjargal, Gantsetseg Garmaa, Unaganshagai Adiya, Tumenulzii Tumurbaatar, Khulan Dorjnamjil, Enkhtsetseg Tserenkhuu, Sumiya Erdenenbaatar, Enkhjargal Tsendjav, Nomin Enkhamgalan, Chuluun-Erdene Achtai, Yagaantsetseg Talhaasuren, Tuya Byambasuren, Erdenetuya Ganbaatar, Erkhembulgan Purevdorj, Adrian R. Martineau

Research output: Contribution to journalArticlepeer-review

Abstract

Objective
To determine whether weekly oral vitamin D supplementation influences grip strength, explosive leg power, cardiorespiratory fitness or spirometric lung volumes in Mongolian schoolchildren.

Methods
Multicentre, randomised, placebo-controlled clinical trial conducted in children aged 6–13 years at baseline attending 18 schools in Ulaanbaatar. The intervention was weekly oral doses of 14 000 IU vitamin D3 (n=4418) or placebo (n=4433) for 3 years. Outcome measures were grip strength, standing long jump distance and serum 25-hydroxyvitamin D (25(OH)D) concentrations (determined in all participants), peak oxygen uptake (VO2peak, determined in a subset of 632 participants using 20 m multistage shuttle run tests) and spirometric outcomes (determined in a subset of 1343 participants).

Results
99.8% of participants had serum 25(OH)D concentrations <75 nmol/L at baseline, and mean end-study 25(OH)D concentrations in children randomised to vitamin D versus placebo were 77.4 vs 26.7 nmol/L (mean difference 50.7 nmol/L, 95% CI 49.7 to 51.4). However, vitamin D supplementation did not influence mean grip strength, standing long jump distance, VO2peak, spirometric lung volumes or peak expiratory flow rate, either overall or within subgroups defined by sex, baseline 25(OH)D concentration <25 vs ≥25 nmol/L or calcium intake <500 vs ≥500 mg/day.

Conclusion
A 3-year course of weekly oral supplementation with 14 000 IU vitamin D3 elevated serum 25(OH)D concentrations in Mongolian schoolchildren with a high baseline prevalence of vitamin D deficiency. However, this intervention did not influence grip strength, explosive leg power, peak oxygen uptake or spirometric lung volumes, either overall or in subgroup analyses.

Trial registration number
NCT02276755.
Original languageEnglish
Article numbere002018
Number of pages12
JournalBMJ Open Sport and Exercise Medicine
Volume10
Issue number3
DOIs
Publication statusPublished - 26 Sept 2024

Bibliographical note

Publisher Copyright:
© Author(s) (or their employer(s)) 2024.

Keywords

  • Children's health and exercise
  • Fitness testing
  • Nutrition

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