b'GUT-LUNG AXISAlthough seemingly distant organs, researchers are beginning to understand how health and functioning of the gut and lungs are linked. Dysbiosis of the GI microbiota has been associated with immune and inflammatory perturbations in the lungs 10 . The GI and respiratory tract, along with the urogenital tract, are linked through the common mucosal immune system. The mucosal immune system acts to identify, neutralise, and remove foreign antigens, promotes immunotolerance and maintains homeostasis for normal physiological processes. As these mucosal surfaces are continuously exposed to pathogens, they are highly vulnerable to infection. The GI microbiota has been shown to modulate immune function at distal mucosal interfaces, including the lungs 11 . Although not as dense as the gut microbiota, the lungs harbour their own specific, diverse microbial community. Dietary strategies to promote a healthy and diverse microbiota, more specifically to increase production of SCFAs, have begun to be explored in the prevention and management of inflammation and infection of the respiratory tract. GUT MICROBIOTAMAMPsTLRNEUROTRANSMITTERS &NEUROACTIVEMETABOLITESDENDRITICCELLENTEROCYTESSCFA B-CELLMUCCOUS LAYERENTEROENDOCRINEENTERIC CELLSNERVE slgACELLCYTOKINES,TNF-, IL-1,IL-6CCK, GLP-1CATECHOLAMINES &GLUCOCORTICOIDSPSYCHOLOGICAL STRESS IMMUNODEPRESSIONOVERREACHING EXPOSURE TOCHRONIC POOR SLEEP FOREIGN PATHOGENSQUANTITY AND QUALITYA. Microbes in the GIT ferment dietary fibre and polyphenols to produce SCFAs, neurotransmitters and other neuroactive metabolites. Dietary factors influence microbial composition and metabolite production. B. SCFAs, neurotransmitters and neuroactive metabolites enter systemic circulation. C. Microbe-associated molecular patterns (MAMPs) and antigens in food and microbes stimulate toll-like receptors (TLRs) and tolerogenic immune response. D. Enteroendocrine cells release hormones that regulate appetite and metabolism. SCFAs influence hormone production. E. Stimulation of hypothalamic-pituitary-adrenal (HPA) axis release catecholamines and glucocorticoids. Stress hormones trigger ENS, modify bacterial composition and may damage tight junction proteins and epithelial barrier. Chronic stimulation of HPA axis may depress immune function. F. Inflammatory markers and other immune signals relayed between the mucosal immune system.We are now beginning to understand how our microbiota can be factored into these nutrition strategies. In this case series, we explore common scenarios that challenge the athletes immune and/or GI systems. These include:Intensified training & competition Exercise-induced GI symptomsTravel Plant-based dietsStress and performance anxiety The older athleteIn this ebook, performance nutritionists Mhairi Keil and Lucy Wainwright provide examples of nutrition strategies they use to support their athletes. Disclaimer: Nutrition strategies vary between individuals and the strategies shown here are examples only.3'