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Why don’t serum vitamin D concentrations associate with BMD by DXA? A case of being ‘bound’ to the wrong assay? Implications for vitamin D screening
  1. Richard J Allison1,2,3,
  2. Abdulaziz Farooq4,
  3. Anissa Cherif4,
  4. Bruce Hamilton5,
  5. Graeme L Close2,
  6. Mathew G Wilson2,4,6
  1. 1Department of Exercise and Sport Science, ASPETAR, Orthopaedic and Sports Medicine Hospital, Doha, Qatar
  2. 2Research Institute for Sport and Exercise Science, Liverpool John Moores University, Auckland, UK
  3. 3Arsenal Football Club, London, UK
  4. 4Athlete Health and Performance Research Centre, ASPETAR, Orthopaedic and Sports Medicine Hospital, Doha, Qata
  5. 5Department of Sports Medicine, High Performance Sport New Zealand, Auckland, Australia
  6. 6Research Institute of Sport and Exercise Sciences, University of Canberra, Australia
  1. Correspondence to Richard J Allison, Arsenal Football Club; rallison{at}arsenal.co.uk

Abstract

Background The association between bone mineral density (BMD) and serum25-hydroxyvitamin D (25(OH)D) concentration is weak, particularly in certain races (eg, BlackAfrican vs Caucasian) and in athletic populations. We aimed to examine if bioavailable vitamin D rather than serum 25(OH)D was related to markers of bone health within a racially diverse athletic population.

Methods In 604 male athletes (Arab (n=327), Asian (n=48), Black(n=108), Caucasian (n=53)and Hispanic (n=68)), we measured total 25(OH)D, vitamin D-binding protein and BMD by DXA. Bioavailable vitamin D was calculated using the free hormone hypothesis.

Results From 604 athletes, 21.5% (n=130) demonstrated severe 25(OH)D deficiency, 37.1% (n=224) deficiency, 26% (n=157) insufficiency and 15.4% (n=93) sufficiency. Serum 25(OH)D concentrations were not associated with BMD at any site. After adjusting for age and race, bioavailable vitamin D was associated with BMD (spine, neck and hip). Mean serum vitamin D binding protein concentrations were not associated with 25(OH)D concentrations (p=0.392).

Conclusion Regardless of age or race, bioavailable vitamin D and not serum 25(OH)D was associated with BMD in a racially diverse athletic population. If vitamin D screening is warranted, clinicians should use appropriate assays to calculate vitamin D binding protein and bioavailable vitamin D levels concentrations than serum 25(OH)D. In turn, prophylactic vitamin D supplementation to ‘correct’ insufficient athletes should not be based on serum 25(OH)D measures.

  • Bone Mineral Density
  • Athlete
  • Biochemistry

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Footnotes

  • Contributors RJA: lead for study, study design, data collection and preparation of manuscript. AF: data analysis. AK: sample analysis. BH: interpretation of data and revision of manuscript for intellectual content. GLC: interpretation of data and revision of manuscript for intellectual content. MGW: study design, data collection and preparation of manuscript.

  • Competing interests None declared.

  • Patient consent Patients completed Aspetar informed consent in Arabic or English.

  • Ethics approval Qatar Anti-Doping Laboratory Ethics Board.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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