Abstract

Purpose. To investigate the relation between vitamin D status and pro- and anti-inflammatory cytokines (as markers of inflammation and immune system function) in an athletic population. Methods. We analyzed serum and plasma extracted from fasting blood samples in nineteen healthy, endurance-trained athletes for vitamin D status (serum 25-hydroxyvitamin D (25(OH)D)) and plasma concentrations of the pro-inflammatory cytokines TNF-α and INF-γ, as well as the anti-inflammatory cytokines IL-4 and IL-10. Participants were on a standardized diet and exercise regimen, and blood samples were obtained at least 36 hours after the last exercise bout. Simple regression analysis was used to determine significant relations between vitamin D status and selected cytokine concentrations. Results. 42% of participants were of insufficient vitamin D status (25(OH)D < 32ng/mL). Concentrations of TNF-α and IL-4 were variable, ranging from 23.5-290.8 pg/mL and 0-252.1 pg/mL, respectively. Concentrations of INF-γ and IL-10 were minimal, with observed means of 6.7±7.0 pg/mL and 4.8±5.1 pg/mL, respectively. After logarithmic transformation, regression analysis of TNF-α and 25(OH)D concentrations revealed a significant inverse relationship (p<0.001). Regression analyses between 25(OH)D and the remaining cytokines, INF-γ, IL-4, and IL-10 were not significant (p=0.477, 0.694, 0.673, respectively). Conclusions. A surprisingly high proportion of the outdoor athletes studied exhibited insufficient serum vitamin D concentrations. Lower vitamin D status was significantly associated with higher concentrations of the inflammatory cytokine TNF-α. The increased inflammation in athletes with lower vitamin D stores could put them at greater risk for infection or inflammation-related injury.