Competitive combat athletes are routinely exposed to high training loads, rapid weight-making practices, psychological stress, and frequent injuries-all of which may adversely affect the gut microbiome and, consequently, multiple physiological systems relevant to performance. Growing scientific interest in the role of probiotics and host-microbiome interactions suggests that targeted modulation of gut bacteria may offer functional benefits for athletes. This narrative review synthesizes current evidence on probiotics and microbiome-mediated pathways influencing performance, recovery, and health in combat-sports athletes. A comprehensive literature search was conducted across PubMed, Web of Science, and Google Scholar, with no date limits, including studies published up to October 2025. Search terms covered the gut microbiome, probiotics, athletic performance, combat sports, gastrointestinal barrier function, immune responses, psychological factors, nutrient absorption, hypoxia, weight cutting, and sex-specific considerations. Reference lists of relevant reviews and grey literature were manually screened. Across the available literature, probiotic supplementation has been associated with a range of effects that could be relevant to combat athletes. Evidence, largely from non‑combat and mixed‑population studies, suggests that probiotics may influence several physiological systems, including: (1) inflammatory and oxidative stress responses and injury rehabilitation; (2) immune function and upper respiratory tract infection outcomes; (3) gastrointestinal permeability and nutrient absorption, particularly after rapid weight loss; (4) psychological factors via the gut-brain axis; (5) muscle recovery through inflammatory and metabolic pathways; (6) body composition and weight regulation; (7) oral and skin microbiome composition; and (8) gut microbial changes during hypoxia or hormonal fluctuations. However, most of these findings are indirect, with very few studies conducted specifically in competitive combat‑sport athletes, and the overall evidence base remains heterogeneous. Probiotic and gut microbiome-targeted strategies may serve as potential adjunctive strategies to support health, recovery, and performance in combat athletes. However, because the current evidence is largely derived from non-combat and predominantly male populations, strain-, dose-, and sport-specific recommendations cannot yet be made. There is a clear need for randomized controlled trials in combat-sport athletes-including women-that employ standardized probiotic protocols and sport-specific outcome measures.
