| Summary: | It is now well established that exercise of a strenuous and/or prolonged nature can lead to transient perturbations in immune function. The clinical significance of participating in such acute bouts of exercise in combination with other life stressors (e.g. inadequate nutrition) may be an increased incidence of upper respiratory illness (URI) (e.g. sore throat, runny nose). Many proposed nutritional countermeasures to exercise-induced immune dysfunction have been shown to be ineffective. The aims of this thesis were to determine the effects of bovine colostrum (COL) on in vitro and in vivo measures of immunity taken at rest and/or following prolonged (≥ 2 h) exercise and the incidence of URI during regular training in active males. Study 1 (Chapter 3) demonstrated that acute COL supplementation improved the recovery of bacterial stimulated neutrophil degranulation and enhanced salivary lysozyme concentration following 2.5 h of cycling. There was also greater fMLP-stimulated oxidative burst throughout the COL trial compared to PLA. These effects are suggested to be partly due to components and/or metabolites of COL that become bioavailable following digestion of the supplement which may explain why Study 2 (Chapter 4) demonstrated a greater effect on fMLP-stimulated oxidative burst with 4 weeks of COL supplementation. Study 3 (Chapter 5) found a lower proportion of URI days and lower number of URI episodes with 12 weeks of COL supplementation. Although there was no effect on selected measures of in vitro immune function taken at rest (fMLP oxidative burst, salivary secretory IgA and antimicrobial peptides), COL did blunt increases in salivary bacterial load over the winter period, which may provide a novel marker of in vivo immunity. Despite no effect of prior infection with Epstein-Barr virus (EBV) on URI incidence in Study 4 (Chapter 6), those who were seropositive and undergoing COL supplementation had a lower number of URI days vii than seronegative counterparts. Study 5 (Chapter 7) observed a lack of effect of COL supplementation on the overall magnitude of an in vivo measure of T-cell-mediated immunity to a novel antigen following prolonged exercise but there was evidence that COL may increase the sensitivity of responses to such antigenic challenge.
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