Vitamin D deficiency (˂25nmol/L) and insufficiency (˂50nmol/L) has become an increasingly popular topic. Current research focusses upon the potential ergogenic effects of vitamin D (vitD) in sporting performance; however, the relationship between vitD (dietary intake and nutritional status) and bone health within a University athlete cohort remains under-investigated. Therefore, the aims of this Thesis were to (1) examine vitD status longitudinally across the University competitive seasons and; (2) examine the implications that vitD deficiency/ insufficiency may have upon physical performance parameters or bone health.

In the first study, fifty-seven competitive University level- athletes from varied sports were observed from autumn to spring. Radial bone mineral density (BMD) and physical performance parameters were investigated; for the analysis of vitD and parathyroid hormone, blood samples were collected. Within the cohort 7% presented with deficiency during the autumn; increasing to 44% during spring. However, this did not have a significant effect upon physical performance and bone health despite an average status of 31.5±16.4 nmol/L in spring.

In the second study, 34 University athletes and sixteen sedentary students were recruited and followed from spring to summer. Whole body, hip and tibial scans were conducted to determine BMD and bone mineral content (BMC). Physical performance parameters including jump height, aerobic fitness, muscular strength and blood biochemistry were also collected. During the summer term, 26% of the cohort were vitD insufficient. Moreover, an insufficient vitD status was associated with a lowered jump height (p=0.015) but not aerobic fitness (p=0.07). There was also a significant positive relationship between vitD status, femoral neck BMC (r=0.685; p˂0.02) and BMD (r=0.679; p˂0.02). Our results show that BMD was higher in weight bearing athletes. The final study found that racket sport athletes had a significantly superior bone profile in their dominant arm when contrasted to controls.

Overall, these findings suggest that an insufficient vitD status was associated with lower indices of muscular power and aerobic fitness in University students. Therefore, being vitD replete may not only play an important role in musculoskeletal health but could also be a key determining factor in athletic performance.