Nutritional strategies to reduce fatigue in athletes and active people

This doctoral thesis investigates the potential of short-chain fatty acids (SCFAs) and probiotics as nutritional strategies to reduce fatigue and enhance health, performance, and recovery in athletes and physically active individuals. Grounded in the emerging understanding of the gut microbiome as a key regulator of host physiology, the research explores how microbiota-derived metabolites—particularly acetate, propionate, and butyrate—may influence immune function, inflammation, energy metabolism, and exercise capacity. Chapter 2 provides a comprehensive narrative review of the current literature on SCFAs in cellular, animal, and human models. The evidence suggests that SCFAs may support athletic health by enhancing mucosal and systemic immunity, reducing susceptibility to respiratory infections, modulating inflammatory responses associated with exercise-induced muscle damage, and contributing to energy homeostasis. Although mechanistic data are promising, especially regarding immunoregulation and metabolic signaling pathways (e.g., G-protein coupled receptors and HDAC inhibition), human performance-based evidence remains limited, highlighting the need for targeted clinical research in athletic populations. Chapter 3 presents a two-phase experimental investigation of a novel multi-strain Lactobacillus consortium derived from elite athletes. The study examined its effects on sleep quality, exercise recovery, and gut microbiome composition in both elite football players and the general population. Findings provide proof-of-concept evidence for a sleep–exercise–microbiome nexus, suggesting that probiotic supplementation may beneficially modulate host–microbe interactions relevant to recovery and well-being. Chapter 4 reports a cross-sectional survey exploring current perceptions and practices regarding probiotic use in professional football. The results reveal growing interest but considerable heterogeneity in implementation, underscoring the need for evidence-based guidelines. Overall, this thesis advances understanding of microbiome-targeted nutritional strategies and lays the foundation for future translational research aimed at optimizing athlete health and performance through gut-mediated interventions.