Low serum 25-hydroxyvitamin D [25(OH)D] concentrations are associated with a high risk of insulin resistance and Type 2 diabetes mellitus in adults. However, it is unknown whether this is the case for American collegiate football and rugby football athletes. This study investigated the associations between serum 25(OH)D concentrations and glucose profiles in male collegiate football athletes. Thirty-four collegiate athletes (13 American football players and 21 rugby football players) aged 21 years were recruited. Their body fat percent and visceral fat area were measured by dual-energy X-ray absorptiometry and magnetic resonance imaging, respectively. The participants completed an oral glucose tolerance test (75 g glucose) with venous blood samples obtained at time points 0, 30, 60, 90, and 120 min for the determination of plasma glucose and serum insulin concentrations. Fasting serum 25(OH)D concentrations were also measured. The prevalence of vitamin D deficiency and insufficiency was 17.6% and 58.8%, respectively. The serum 25(OH)D concentrations were negatively associated with the increments in the areas under the curve (iAUC) for glucose (r = -.429, p = .011) and were borderline significantly correlated with the Matsuda index (r = -.303, p = .082). No relationships were observed between the serum 25(OH)D concentrations and other glucose profiles. Multiple stepwise regression analysis of glucose iAUC concentrations as the dependent variable indicated that the serum 25(OH)D concentrations, but not body fat indicators, were independently associated with glucose iAUC (β = -0.390, p = .025). The serum 25(OH)D concentrations were only an independent predictor for glucose iAUC in male collegiate football athletes, suggesting that increased 25(OH)D concentrations would be helpful for maintaining glucose homeostasis.
Keywords: glucose response; visceral fat; vitamin D.