Association of Gut Microbiota With Performance Level Among Iranian Professional and Semi-Professional Runners: A Cross-Sectional Study.

Background and Aims: The gut microbiota is a diverse ecosystem with the potential to significantly enhance athletic metabolic capacity. Emerging research indicates that the gut microbiota plays a crucial role in modulating energy metabolism, immune function, oxidative stress, skeletal muscle dynamics, and neuroendocrine regulation, all of which are essential for optimizing athletic performance. This study investigates the composition of a selection of gut microbiota among Iranian professional and semi-professional runners from three different disciplines including endurance, middle-distance, and speed runners, and examines their association with performance levels. Methods: Fresh stool samples of 60 runners were collected and the relative abundance of a selection of intestinal microbiota at various taxonomic levels was assessed by RT-qPCR. The relative abundance of the selected microbiota revealed distinct patterns across different types of runners. Results: Predominant taxa in professional groups were Bacteroidetes, Firmicutes, and Prevotella spp., while semi-professional groups had a higher abundance of Firmicutes, Bacteroidetes, Actinobacteria, Clostridia, and Prevotella spp. Akkermansia muciniphila was mostly abundant among speed runners (40.95%), followed by endurance (27.025%) and middle-distance runners (23.525%). Fusobacterium nucleatum was more abundant in middle-distance (34.9%) and endurance runners (34.3%) compared to speed runners (22.3%). A negative correlation was found between performance levels and the abundance of Actinobacteria, Enterobacteriaceae, E-proteobacteria, Bifidobacterium spp., and Faecalibacterium prausnitzii, while a positive correlation was observed with Methanobrevibacter smithii. Conclusion: This study illuminates the distinct microbial taxa detected in professional and semi-professional runners, which corroborates the relationship between running disciplines and the gut microbiota composition, as well as their impact on performance levels.