Factors influencing upper respiratory tract illness incidence in athletes: the important role of vitamin D
2015-06-19T14:04:59Z (GMT) by
Firstly, the aims of the study were to investigate the influences of various factors, sex differences, Cytomegalovirus/Epstein-Barr virus (CMV/EBV) serostatus and vitamin D concentrations on respiratory illness incidence and immune function during the winter months in a student cohort of endurance athletes. In Chapter 3, the findings of the study concur with recent reports of illness incidence at major competitive games which indicate that female athletes may be more susceptible than their male counterparts to upper respiratory tract illness (URTI) symptoms and that lower oral-respiratory mucosal immunity may, in part, account for this. It was also found that previous coinfection with CMV and EBV might promote protective immune surveillance to lower the risk of URTI. In addition, it can be concluded that athletes with low plasma vitamin D concentrations may have a higher risk of URTI and suffer more severe symptoms when URTI is present. This may be due to impaired mucosal and systemic immunity as secretory immunoglobulin A (SIgA) secretion, cathelicidin levels and antigen-stimulated pro-inflammatory cytokine production appear to be increased by vitamin D-dependent mechanisms. A series of follow-up studies were also conducted to examine the effect of vitamin D on mucosal and systemic immunity in athletes. In Chapter 4, it was reported that the influence of vitamin D on circulating cytokines might be different in athletes compared with non-athletes and that both pro-inflammatory and anti-inflammatory cytokine production by multi-antigen stimulated whole blood culture were not influenced by 1,25-dihydroxy vitamin D (1, 25(OH)2D) iconcentrations within the normal healthy range. In Chapter 5, it was found that 5000 IU of vitamin D3 supplementation daily appears to have a beneficial effect in up-regulating the expression of SIgA and cathelicidin in athletes during a winter training period. Nevertheless, the findings reported in Chapter 6 showed that there were no significant effects of vitamin D status and a 4-week period of daily high does vitamin D3 supplementation on salivary antimicrobial protein (AMP) responses to prolonged exercise. In conclusion, a series of studies in this thesis have demonstrated the influence of various factors (sex differences, CMV/EBV serostatus and vitamin D concentrations) on susceptibility to URTI among athletes. Moreover, it was suggested that vitamin D3 supplementation could have a positive effect on immune function and lead to decreased incidence of respiratory infections.