Emerging Relationships Between Vitamin D Status, Physical Activity Habits, and Immune Indices in College-Aged Females

Abstract. It has been determined that individuals who are regularly physically active have more favorable inflammatory profiles; less is known about how vitamin D levels can impact inflammation. This study explored the relationship between inflammatory indices in physically active (PA) and not physically active (NPA) individuals with 25-hydroxyvitamin D (25OHD) concentrations either above or below optimal concentrations. All female subjects (n = 63, age 19 – 35 years) were evaluated for body composition, maximal aerobic capacity (VO2peak), and anaerobic power (Wingate). Blood samples were analyzed for 25OHD and C-reactive protein (CRP), stimulated with lipopolysaccharide (LPS) and assessed for interleukin-6 (IL-6) production, and used for flow cytometric analysis. PA (n = 30) had higher 25OHD levels (45.2 ± 2.7 vs. 17.05 ± 1.4 ng / mL; p = 0.015), higher VO2peak (p < 0.0001), lower body weight (p = 0.039) and lower estimated percent body fat (p = 0.011) compared to NPA (n = 33). PA also had lower LPS-stimulated IL-6 production compared to NPA (p = 0.0163), although there were no differences between resting CRP concentrations. NPA with optimal 25OHD had fewer total monocytes, CD14⁺CD16^-cells, CD14⁺CD16⁺ cells, and decreased TLR4 expression on CD14⁺CD16⁺ cells compared to NPA with suboptimal 25OHD (< 32 ng / mL). In summary, regular physical activity was associated with higher serum 25OHD, healthier measures of body composition, and reduced stimulated IL-6 production. However, optimal vitamin D status was not associated with anti-inflammatory benefits beyond those which are provided by regular physical activity.