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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

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Original article
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. 1 Department of Exercise and Sport Science, ASPETAR, Orthopaedic and Sports Medicine Hospital, Doha, Qatar
  2. 2 Research Institute for Sport and Exercise Science, Liverpool John Moores University, Auckland, UK
  3. 3 Arsenal Football Club, London, UK
  4. 4 Athlete Health and Performance Research Centre, ASPETAR, Orthopaedic and Sports Medicine Hospital, Doha, Qata
  5. 5 Department of Sports Medicine, High Performance Sport New Zealand, Auckland, Australia
  6. 6 Research 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

https://doi.org/10.1136/bjsports-2016-097130

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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.