. 2024 Sep 26;10(3):e002019.

doi: 10.1136/bmjsem-2024-002019. eCollection 2024.

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^{1

2}, Lisa Micklesfield^{3

4}, Stephanie Hemmings⁵, Neil Walker⁶, Justine Stewart^{1

2}, David A Jolliffe⁷, Amy E Mendham^{4

8}, Jonathan C Y Tang^{9

10}, Cyrus Cooper^{11

12}, Nicholas C Harvey^{11

12}, Robert J Wilkinson^{13

14

15}, Adrian R Martineau⁵

Affiliations

¹ Desmond Tutu HIV Centre, Institute of Infectious Diseases & Molecular Medicine, University of Cape Town, Observatory, South Africa.
² Department of Medicine, University of Cape Town, Observatory, South Africa.
³ Health through Physical Activity, Lifestyle and Sport Research Centre (HPALS), Division of Physiological Sciences, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.
⁴ SAMRC/Wits Developmental Pathways for Health Research Unit, Department of Paediatrics, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
⁵ School of Sport and Health Sciences, University of Brighton, Eastbourne, UK.
⁶ Wolfson Institute of Population Health, Faculty of Medicine and Dentistry, Queen Mary University of London, London, UK.
⁷ Blizard Institute, Faculty of Medicine and Dentistry, Queen Mary University of London, London, UK.
⁸ Riverland Academy of Clinical Excellence, Riverland Mallee Coorong Local Health Network, South Australia Health, South Australia, Australia.
⁹ Norwich Medical School, University of East Anglia, Norwich, UK.
¹⁰ Departments of Laboratory Medicine, Clinical Biochemistry and Departments of Diabetes and Endocrinology, Norfolk and Norwich University Hospital NHS Foundation Trust, Norwich, UK.
¹¹ MRC Lifecourse Epidemiology Centre, University of Southampton, Southampton, UK.
¹² NIHR Southampton Biomedical Research Centre, University of Southampton, and University Hospital Southampton NHS Foundation Trust, Southampton, UK.
¹³ Centre for Infectious Diseases Research in Africa, Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Observatory, South Africa.
¹⁴ The Francis Crick Institute, London, UK.
¹⁵ Imperial College London, London, UK.

PMID: 39345832
PMCID: PMC11429360
DOI: 10.1136/bmjsem-2024-002019

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 et al. BMJ Open Sport Exerc Med. 2024.

. 2024 Sep 26;10(3):e002019.

doi: 10.1136/bmjsem-2024-002019. eCollection 2024.

Authors

Affiliations

¹ Desmond Tutu HIV Centre, Institute of Infectious Diseases & Molecular Medicine, University of Cape Town, Observatory, South Africa.
² Department of Medicine, University of Cape Town, Observatory, South Africa.
³ Health through Physical Activity, Lifestyle and Sport Research Centre (HPALS), Division of Physiological Sciences, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.
⁴ SAMRC/Wits Developmental Pathways for Health Research Unit, Department of Paediatrics, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
⁵ School of Sport and Health Sciences, University of Brighton, Eastbourne, UK.
⁶ Wolfson Institute of Population Health, Faculty of Medicine and Dentistry, Queen Mary University of London, London, UK.
⁷ Blizard Institute, Faculty of Medicine and Dentistry, Queen Mary University of London, London, UK.
⁸ Riverland Academy of Clinical Excellence, Riverland Mallee Coorong Local Health Network, South Australia Health, South Australia, Australia.
⁹ Norwich Medical School, University of East Anglia, Norwich, UK.
¹⁰ Departments of Laboratory Medicine, Clinical Biochemistry and Departments of Diabetes and Endocrinology, Norfolk and Norwich University Hospital NHS Foundation Trust, Norwich, UK.
¹¹ MRC Lifecourse Epidemiology Centre, University of Southampton, Southampton, UK.
¹² NIHR Southampton Biomedical Research Centre, University of Southampton, and University Hospital Southampton NHS Foundation Trust, Southampton, UK.
¹³ Centre for Infectious Diseases Research in Africa, Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Observatory, South Africa.
¹⁴ The Francis Crick Institute, London, UK.
¹⁵ Imperial College London, London, UK.

PMID: 39345832
PMCID: PMC11429360
DOI: 10.1136/bmjsem-2024-002019

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 (VO_2peak, 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, VO_2peak 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.

Keywords: Children's health and exercise; Fitness testing; Nutrition.

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Conflict of interest statement

ARM declares receipt of funding in the last 36 months to support vitamin D research from the following companies who manufacture or sell vitamin D supplements: Pharma Nord, DSM Nutritional Products, Thornton & Ross and Hyphens Pharma. ARM also declares receipt of vitamin D capsules for clinical trial use from Pharma Nord, Synergy Biologics and Cytoplan; support for attending meetings from Pharma Nord Ltd and Abiogen Pharma; receipt of consultancy fees from DSM Nutritional Products and Qiagen; receipt of a speaker fee from the Linus Pauling Institute; participation on Data and Safety Monitoring Boards for the VITALITY trial (Vitamin D for Adolescents with HIV to reduce musculoskeletal morbidity and immunopathology, Pan African Clinical Trials Registry ref PACTR20200989766029) and the Trial of Vitamin D and Zinc Supplementation for Improving Treatment Outcomes Among COVID-19 Patients in India (ClinicalTrials.gov ref NCT04641195) and unpaid work as a Programme Committee member for the Vitamin D Workshop.

Figures

**Figure 1. Participant flow diagram. QFT-Plus, QuantiFERON-TB Gold Plus.**

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

Affiliations

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

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Affiliations

Abstract

Conflict of interest statement

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