Bovine colostrum is homologous in composition to human colostrum but contains greater concentrations of key bioactive components that contribute directly to growth and immunity. It has been used by humans to treat and prevent enteric pathogens and to promote wound healing and intestinal repair. Moreover, bovine colostrum has been promoted and used by athletes as a supplement to enhance immune function and improve exercise performance. This is despite limited data in support of its value to athletes and the relative absence of strong data that identify mechanisms that could improve exercise performance and immune function. The aim of the three studies that comprise this thesis was therefore to investigate the influence of a bovine colostrum protein concentrate (CPC) on immune variables, hormone concentrations, autonomic activity and exercise performance in highly-trained endurance cyclists. Study one involved monitoring exercise performance and immune variables during an eight week bovine CPC supplementation period, which included five consecutive days of high-intensity training (HIT). Twenty-nine highly-trained male road cyclists completed an initial 40-km time trial (TT40) and were then randomly assigned to either a supplement (n=14, 10 g bovine CPC per day) or placebo group (n=15, 10 g whey protein concentrate per day). Following five weeks of supplementation, the cyclists completed a second TT40 before undertaking five consecutive days of high-intensity training (HIT) that included another TT40. A final TT40 was completed one week following the HIT. Venous blood and saliva samples were collected immediately before and after each TT40, and upper respiratory illness symptoms were recorded over the experimental period. Supplementation with bovine CPC elicited improvements in TT40 performance at the end of the HIT period, when compared to the placebo group, (1.9±2.2%; mean±90% confidence limits) and maintained ventilatory threshold following the HIT (4.6±4.6%). When compared to the placebo group, bovine CPC supplementation significantly increased pre-exercise serum soluble tumour necrosis factor receptor 1 during the HIT period (p<0.039). Supplementation also suppressed the post-exercise decrease in cytotoxic/suppressor T cells during the HIT period (bovine CPC=-Bovine colostrum is homologous in composition to human colostrum but contains greater concentrations of key bioactive components that contribute directly to growth and immunity. It has been used by humans to treat and prevent enteric pathogens and to promote wound healing and intestinal repair. Moreover, bovine colostrum has been promoted and used by athletes as a supplement to enhance immune function and improve exercise performance. This is despite limited data in support of its value to athletes and the relative absence of strong data that identify mechanisms that could improve exercise performance and immune function. The aim of the three studies that comprise this thesis was therefore to investigate the influence of a bovine colostrum protein concentrate (CPC) on immune variables, hormone concentrations, autonomic activity and exercise performance in highly-trained endurance cyclists. Study one involved monitoring exercise performance and immune variables during an eight week bovine CPC supplementation period, which included five consecutive days of high-intensity training (HIT). Twenty-nine highly-trained male road cyclists completed an initial 40-km time trial (TT40) and were then randomly assigned to either a supplement (n=14, 10 g bovine CPC per day) or placebo group (n=15, 10 g whey protein concentrate per day). Following five weeks of supplementation, the cyclists completed a second TT40 before undertaking five consecutive days of high-intensity training (HIT) that included another TT40. A final TT40 was completed one week following the HIT. Venous blood and saliva samples were collected immediately before and after each TT40, and upper respiratory illness symptoms were recorded over the experimental period. Supplementation with bovine CPC elicited improvements in TT40 performance at the end of the HIT period, when compared to the placebo group, (1.9±2.2%; mean±90% confidence limits) and maintained ventilatory threshold following the HIT (4.6±4.6%). When compared to the placebo group, bovine CPC supplementation significantly increased pre-exercise serum soluble tumour necrosis factor receptor 1 during the HIT period (p<0.039). Supplementation also suppressed the post-exercise decrease in cytotoxic/suppressor T cells during the HIT period (bovine CPC=- 1.0±2.7%, placebo=-9.2±2.8%; mean±SE, p=0.017) and during the following week (bovine CPC=1.4±2.9%, placebo=-8.2±2.8%, p=0.004). In addition, bovine CPC supplementation prevented a post-exercise decrease in serum IgG2 concentration at the end of the HIT period (bovine CPC=4.8±6.8%, p=0.88; placebo=-9.7±6.9%, p=0.013) and there was a trend towards reduced incidence of upper respiratory illness symptoms in the bovine CPC group (p=0.055). Study one demonstrated that low dose bovine CPC supplementation elicited improvements in TT40 performance during a HIT period and maintained ventilatory threshold following five consecutive days of HIT. Supplementation was also found to modulate immune variables during normal training and following an acute period of intense exercise, which may have contributed to the trend toward reduced upper respiratory illness in the bovine CPC group. The maintenance of performance, prevention of post-exercise suppression of IgG2 and cytotoxic/suppressor T cells and increase in anti-inflammatory serum soluble tumour necrosis factor receptor 1 suggest that bovine CPC supplementation is beneficial to cyclists during a period of high-intensity training. The aim of Study two was to investigate the hormonal, immune and autonomic responses of competitive cyclists over a five-day stage race following eight weeks of bovine CPC supplementation. Ten highly-trained male road cyclists were randomly assigned to a placebo (n=6, 10 g whey protein concentrate/day) or bovine CPC group (n=4, 10 g bovine CPC/day). Cyclists provided a baseline saliva sample before commencing supplementation that culminated in a five day competitive cycle race. The cyclists provided daily saliva samples and heart rate variability (HRV) was measured on each day of the race. A Profile of Mood States questionnaire was completed on days one, three and five of the race and cyclists recorded upper respiratory illness symptoms throughout the experimental period. While there was no influence of bovine CPC on salivary IgA, supplementation maintained testosterone concentrations over the competition period (p<0.05) and prevented a decrease in parasympathetic activity (p<0.05). There was also a trend towards improved mood state (p=0.06) in the bovine CPC group. These data indicate that bovine CPC supplementation may prevent disturbances in autonomic function and the hypothalamic-pituitary-gonadal axis associated with consecutive days of cycle racing The aim of study three was to assess whether bovine CPC would directly stimulate cytokine production of peripheral blood mononuclear cells (PBMC), with and without lipopolysaccharide (LPS) and phytohemagglutinin (PHA) stimulation. Lipopolysaccharide (LPS) was added to cell cultures as a potent enhancer of monocyte and macrophage cytokine release and a model of exercise stress. Phytohemagglutinin was added to PBMC to stimulate T cell proliferation. Blood was sampled from four healthy, male endurance cyclists who had abstained from exercise for 48 hours. PBMC were separated and cultured with bovine CPC concentrations of 0 (control), 1.25, 2.5 and 5% with and without LPS (3µg·mL-1) and PHA (2.5µg·mL-1). Cell supernatants were collected at 6 and 24 hours of culture for the determination of tumour necrosis factor (TNF), interferon (IFN)-y, interleukin (IL)-10, IL-6, IL-4 and IL-2 concentrations. Following six hours of PBMC incubation at 37°C with 5% CO2, IFN-y, IL-10 and IL-2 secretion were increased with increasing concentrations of bovine CPC (p<0.05). In a dose dependent manner, IFN-y and IL-2 remained elevated following 24 hours of incubation (p<0.05). Data from this final study showed that bovine CPC modulates in vitro cytokine production of human PBMC. In conclusion, the present data suggest that bovine CPC supplementation is beneficial to highlytrained cyclists during periods of high-intensity training and competition. Bovine CPC promotes the release of cell mediated cytokines from PBMC and has the potential therefore to influence a number of physiological systems. Supplementation was associated with enhanced recovery over consecutive days of high-intensity training and competition, as evidenced by maintained exercise performance, ventilatory threshold and testosterone concentrations. Bovine CPC modulated immune function, particularly at the end of a HIT period, and there was a trend for reduced incidence of upper respiratory symptoms following bovine CPC supplementation in Study one. The data collectively suggest that bovine CPC supplementation may influence a combination of physiological pathways including the autonomic nervous system and the hypothalamic-pituitary axis.
| Identifer | oai:union.ndltd.org:ADTP/290220 |
| Creators | Shing, Cecilia Mary |
| Source Sets | Australiasian Digital Theses Program |
| Detected Language | English |
Page generated in 0.0034 seconds