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Br J Sports Med. 2018 Apr;52(8):522-526. doi: 10.1136/bjsports-2016-097130. Epub 2017 Aug 10.

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.

Author information

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

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.

KEYWORDS:

Athlete; Biochemistry; Bone Mineral Density

PMID:
28798036
DOI:
10.1136/bjsports-2016-097130
[Indexed for MEDLINE]

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