{"doi":"10.1101/2024.03.27.24304943","title":"Influence of vitamin D supplementation on muscle strength and exercise capacity in Mongolian schoolchildren: a randomised controlled trial","abstract":"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, double-blind, 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 D 3 (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 (VO 2peak , determined in a subset of 632 participants using 20-metre multi-stage shuttle run tests) and spirometric outcomes (determined in a subset of 1,343 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 vs. 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, VO 2peak , spirometric lung volumes or peak expiratory flow rate, either overall or within sub-groups 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 D 3 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 sub-group analyses. KEY MESSAGES What is already known on this topic? Observational studies have reported that vitamin D deficiency associates with reduced muscle strength and peak oxygen uptake in children, but randomised controlled trials (RCT) of vitamin D supplementation to improve grip strength and cardiorespiratory fitness in this age-group have yielded conflicting results. What this study adds This Phase 3 multicentre RCT of vitamin D supplementation, conducted in Mongolian schoolchildren with a high baseline prevalence of asymptomatic vitamin D deficiency, found that a 3-year course of weekly oral supplementation with 14,000 IU vitamin D 3 was effective in elevating serum 25-hydroxyvitamin D concentrations. However this intervention did not influence participants’ grip strength, long jump distance, peak oxygen uptake, spirometric lung volumes or peak expiratory flow rate, either overall or in sub-group analyses. How this study might affect research, practice or policy Taken together with results from another Phase 3 randomised controlled trial of vitamin D supplementation conducted in South African children, our findings do not suggest a role for weekly oral vitamin D supplementation to enhance muscle strength, peak oxygen uptake or respiratory function in schoolchildren in whom rickets has been excluded.","journal":"medRxiv","year":2024,"id":488193,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":2,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9567,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2024-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":1295433,"name":"Stephanie Hemmings","orcid":null,"position":1,"is_corresponding":false},{"id":1295013,"name":"David A. 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