A Quasi-Experimental Trial of the Effects of Cholecalciferol Supplementation on Vitamin D Status Among a Diverse Population of Collegiate Basketball Athletes

Abstract

Background: Vitamin D is a fat-soluble micronutrient commonly found to be clinically deficient in a young, athletic, and otherwise healthy population. A gap remains in scientific literature pertinent to why this discrepancy exists, if particular modalities perpetuate this discrepancy and in what quantity vitamin D3 supplementation beneficially affects vitamin D status. Objective: To assess the prevalence of vitamin D insufficiency in a diverse sample of collegiate basketball athletes and to define the required dosage of vitamin D3 supplementation in order to beneficially affect serum 25-hydroxyvitamin D (25(OH)D), the major circulating metabolite in the human body indicative of vitamin D levels and consequently, one’s current status. Design: This was a quasi-experimental vitamin D intervention trial. Participants were allocated to one of three groups based on their baseline vitamin D status as follows: insufficient (<75 nmol/L) were allocated to 10,000 IU of vitamin D3 daily, sufficient (75- 125 nmol/L) to 5,000 IU of vitamin D3 daily, and optimal (>125 nmol/L) to no supplementation. Baseline assessments were completed at the beginning of pre-season training and at ~5 months follow-up at post season. Demographics, body composition via dual x-ray absorptiometry, skin pigmentation via spectrophotometer and blood sampling for the assessment of serum 25(OH)D were completed. Results: The majority of participants (n=13) were allocated to the high dose supplementation group (10,000 IU daily) vs. n=5 allocated to 5,000 IU daily and n=2 to no supplementation. Overall, 77% of participants allocated to the high dose supplementation group (10,000 IU daily) were male (p=0.005), with olive to dark skin tone (p=0.022), and 85% self-reported as African American (p=0.027). Differences among groups were noted for whole body BMD Z-score (p=0.027) and lean body mass (p=0.004). A dose-response emerged in regard to the change of 25-hydroxyvitamin D concentrations from baseline to follow-up, wherein the 10,000 IU daily group exhibited the greatest change in 25(OH)D concentrations (35.01± 26.96 nmol/L) vs. the 5,000 IU daily group (-9.34± 9.62 nmol/L) and the no supplementation group (-41.57± 11.66 nmol/L, p<0.01). Among those allocated to 10,000 IU daily group, 3 (23%) remained insufficient, 9 (69%) climbed to sufficient status and 1 (8%) reached optimal status at follow-up. No participant in the 5,000 IU group reached optimal status and one of the two participants in the no supplementation group remained at optimal status at follow-up. A significant correlation between the change in 25(OH)D concentrations was observed with baseline 25(OH)D (rs=-0.78, p=0.01) as well as with lean and fat mass percent rs=0.83 and rs=-0.80 respectively, p=0.01). Conclusion: A dosage of 10,000 IU of vitamin D3 supplementation taken daily and allotted sufficient time to see marked improvement will help to mitigate the high prevalence of vitamin D deficiency among collegiate basketball players by beneficially impacting serum 25(OH)D levels. However, this dosage was not enough for all participants to reach vitamin D sufficiency. Further research encompassing a larger sample size of indoor, male and female collegiate athletes with varying degrees of adiposity is needed. Improving vitamin D status may have the potential benefits in maximizing sports performance and efficaciously reduce injury risk among collegiate athletes.