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.

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.

No association between vitamin D deficiency and markers of bone health in athletes.

PURPOSE: Adequate vitamin D (25(OH)D) is required to maintain good bone health, yet many athletes are 25(OH)D deficient. This study sought to examine the relation between serum 25(OH)D and measures of bone health (bone mineral density (BMD) and T-score) in an ethnically diverse athletic population. METHODS: Nine hundred and fifty male athletes presented for precompetition medical assessment in our facility. An additional 436 individuals registered with a Qatari sporting federation (such as sailing, archery, shooting, bowling) but exercising <2 h·wk were used as control population. There were 30 Asian, 242 Black African, 235 Caucasian, 491 from Gulf Cooperation Countries, 336 Middle Eastern, and 52 Persian participants. All individuals undertook bone densitometry and body composition analysis by dual-energy x-ray absorptiometry and serum 25(OH)D evaluation. RESULTS: From 950 athletes, 17.5% demonstrated severe deficiency, 39.2% demonstrated deficiency, 24.5% demonstrated insufficiency, and 18.8% demonstrated sufficiency, compared with 436 controls, 25.9% of whom demonstrated severe deficiency, 46.3% demonstrated deficiency, 19.0% demonstrated insufficiency, and 8.7% demonstrated sufficiency. No athlete presented with a T-score suggestive of osteoporosis (-2.5 SD) or osteopenia (-1.0 SD) at hip total. After adjustment for age, anthropometry, ethnicity, and athletic participation, there was no association between 25(OH)D and any BMD and T-score at any site within athletes. African and Caucasian athletes present with greater (P < 0.05) BMD and T-scores at the spine, neck, and hip total than those of Asian, Gulf Cooperation Countries, Middle Eastern, and Persian ethnicities. Athletes participating in high-impact sports present with higher measures (P < 0.05) of bone health than control participants regardless of 25(OH)D status. CONCLUSIONS: There is no association between 25(OH)D and BMD and T-score for any site within male athletes after adjusting for age, ethnicity, and sporting participation.

Severely vitamin D-deficient athletes present smaller hearts than sufficient athletes.

BACKGROUND: Vitamin D (25(OH)D) deficiency has associations with bowl/colon cancer, arthritis, diabetes, and cardiovascular disease. Many athletes are vitamin D deficient, yet no studies have examined the association between 25(OH)D status and cardiac structure and function in healthy athletes. DESIGN: A total of 506 national-level athletes [football (50%), handball (23%), volleyball (16%), and basketball (11%)] and 244 control participants presented for precompetition medical assessment. Controls were healthy individuals registered with a sporting federation undertaking <2 h of exercise per week. METHODS: All individuals undertook a physical examination, 12-lead electrocardiogram, echocardiogram, and serum 25(OH)D evaluation. RESULTS: From 506 athletes and 244 controls, 23 and 12.3% demonstrated 25(OH)D sufficiency (>30 ng/ml), 30 and 23.4% insufficiency (20-30 ng/ml), 37.2 and 48.8% deficiency (10-20 ng/ml), and 11 and 15.6% severe deficiency (<10 ng/ml). Severely 25(OH)D-deficient athletes present significantly (p < 0.05) smaller aortic root and left atria diameters, intraventricular septum diameter (IVSd), left ventricular diameter during diastole (LVIDd), left ventricular mass (LVM), left ventricular volume during diastole (LVvolD), and right atrial (RA) area than insufficient and sufficient athletes. Furthermore, following logarithmic transformation adjusting 25(OH)D for age, body surface area, ethnicity, and athletic participation, positive associations were observed between 25(OH)D and IVSd, LVIDd, posterior wall thickness during diastole, LVM, and LVvolD in athletes but not in the control participants. CONCLUSIONS: Severely 25(OH)D-deficient athletes present significantly smaller cardiac structural parameters than insufficient and sufficient athletes. Future research should investigate the precise mechanism(s) causing cardiac hypertrophy with increases in serum 25(OH)D in healthy athletes.