Abstract/Summary

Research suggests that the intake of certain foods – often referred to as nutraceuticals, may affect both gastrointestinal health and wellbeing through manipulation of the gut microbiota. This may be particularly beneficial for those who are experiencing physiological or psychological stressors – which can have a noticeable effect on health and wellbeing. A growing body of research suggests that the use of prebiotic supplementation and high fibre diets may modulate the microbiota and attenuate stress responses, whilst also improving cognitive function. Polyphenols, a putative prebiotic also, have demonstrated similar action in vitro and in animal studies. By combining the two supplements it may be possible to garner the benefits of both, whilst reducing the need for costly pharmaceutical treatments when it comes to reducing the physiological effects of stress. Though stress is ubiquitous in daily life, a subset of the population who are often subject to extreme stressors are active military personnel. Such stressors often result in soldiers having severe gastrointestinal diseases and cognitive perturbations such as Post Traumatic Stress Disorder (PTSD). By exploring the potential of beneficial nutritional interventions, it may be possible to establish whether the increased intake of certain nutraceuticals (such as this novel polyphenols and prebiotics) could improve psychological and gut health in combat soldiers and in the general ‘stressed’ population. This work uses both in vitro fermentation work, and in vivo studies to explore whether a combination of these health positive supplements will have superior efficacy than either supplement alone on both the gut microbiome, and the perceived wellbeing of both healthy general populations, and active military personnel under artificial physical stressors. The in vitro fermentation work within this thesis demonstrated positive evidence for the novel combination to be more efficacious than either supplement alone, and when compared to a negative control, with improvements such as increased serotonin, elevated SCFAs such as acetate, and lactate, and positive changes within the gut microbiota. In both human trials, positive changes within the faecal microbiota occurred, as well as potential reductions in pathogenic bacteria that were more acutely obvious in the presence of the novel combination. As well as this, changes in health-related metabolites such as hippurate were evident in those groups that had consumed the novel combination – as well as potential attenuation of stress related blood pressure increases. Wellbeing scores stayed relatively similar throughout the supplementation period, though more research is needed to confirm the effects on perceived mood. The novel combination, throughout both in vitro and in vivo did seem to present superior efficacy, suggesting that this would be a preferential option to either supplement alone, in both populations.