A recent systematic review from a team of Italian researchers analyzed the current state of the science on the relationship between the gut microbiome, training and performance across sports and nutritional strategies. It noted that the interaction between these factors underscores the need to identify targeted microbiome-modulating interventions to optimize athletic performance while preventing potential imbalances in the microbial community.
“The gut microbiome represents a complex ecosystem that influences human physiology through multiple mechanisms, including the modulation of energy metabolism, immune and inflammatory response and the production of bioactive metabolites,” the researchers wrote in the journal Frontiers in Nutrition. “In high-level athletes, the role of the intestinal microbiome appears particularly relevant, emerging as a potential modulator of athletic performance and training adaptations.”
The work was a collaboration between researchers affiliated with the University of Verona, University of Rome and the Massachusetts General Hospital for Children and Harvard Medical School.
The exercised gut microbiome
Research in sports nutrition indicates that athletes tend to have heathier, more diverse gut microbiomes than sedentary individuals and that exercise can beneficially alter the composition and metabolic capacity of the gut microbiota.
According to a 2020 review published in the Journal of the International Society of Sports Nutrition by leading experts in the field, typical features of the exercised gut include a higher abundance of health-promoting bacterial species, increased microbial diversity which promotes resilience, functional pathways and microbial-associated metabolites, stimulation of bacterial abundance that can modulate mucosal immunity and improved barrier functions.
“Understanding the various roles the gut microbiota plays in relation to athletic performance is of great interest to athletes seeking to improve competition outcomes as well as reduce recovery time from training,” wrote the researchers, led by Alex Mohr of the College of Health Solutions at Arizona State University. The paper acknowledged that different sports, athlete profiles and training regimens have distinct effects on the gut microbiota.
Two years later, another review published in Sports Medicine explored the bidirectional relationship between the microbiome and exercise—where a moderate amount of exercise is believed to have a positive effect on gut health and immunity. In contrast, intense and sustained exercise can have a deleterious effect by diverting blood flow away from the gastrointestinal tract..
Based on a presentation by microbiome researcher Paul Cotter, PhD, to the Gatorade Sport Science Institute Expert Panel, the article concluded that exercise’s significant effect on the microbiome “appears to generally be positive, increasing gut microbiome diversity and abundance of health-associated bacteria, with some studies suggesting that this is exercise-modality dependent.” Here, not all exercise is considered equal, with studies suggesting significant microbiome differences in athletes across sports—whether static like weightlifting or dynamic like long-distance running.
“This included an enrichment of species of Bifidobacterium, Lactobacillus, Prevotella and Faecalibacterium in the gut of athletes competing in sports with a high dynamic component and low static component,” the researchers reported, noting a related study that found that cardiovascular exercise has minor, transient effect on microbiome composition.
Irish rugby guts and specific microbial patterns
Dr. Cotter is principal investigator at APC Microbiome Ireland, senior principal research officer at Teagasc Food Research Centre and co-founder of microbiome analysis and sequencing services company SeqBiome. In 2011, he and his team sampled the guts of the Irish national rugby team before the squad headed off to the World Cup in New Zealand. This led to the first published report that exercise increases microbial diversity in humans.
“As expected, athletes and controls differed significantly with respect to plasma creatine kinase (a marker of extreme exercise), and inflammatory and metabolic markers,” the Teagasc research team reported. “More importantly, athletes had a higher diversity of gut micro-organisms, representing 22 distinct phyla, which in turn positively correlated with protein consumption and creatine kinase.”
Further research by Dr. Cotter and his group identified distinct microbiome composition and metabolome across subgroups of elite Irish athletes, many of whom were participating in the 2016 Olympics. It found that, even without dietary changes, differences in the gut microbiome and metabolome between groups suggested that training load or type may be a contributing factor.
“The microbiomes of athletes participating in sports with a high dynamic component were the most distinct compositionally (greater differences in proportions of species), while those of athletes participating in sports with high dynamic and static components were the most functionally distinct (greater differences in functional potential),” they wrote in the Journal of Science and Medicine in Sport. “Additionally, both microbial (fecal) and human (urine) derived metabolites were found to vary between sports classification groups.”
The latest review from the Italian research team—which examined 12 experimental studies and seven reviews published between 2015 and 2025 spanning endurance, strength, power and team sports—also highlighted these distinctive alterations in metabolic profiles and significant correlations between microbial stability and athletic performance.
“Specific microbial patterns emerge according to sport type,” Junior Carlone, lead author on the review, reported. “Endurance athletes show an increase in Veillonella and Prevotella, associated with lactate metabolism, whereas power athletes exhibit distinct microbial adaptations.”
How training is structured also appears to contribute to modulating microbiota composition, with cyclical variations between preparatory and recovery phases, and microbial stability is affected by diet—where “high-carbohydrate strategies seem to maintain microbial stability and support endurance performance, while low-carb/high-fat diets may negatively affect the gut microbiota.”
In addition to significant impacts of nutritional strategies, as well as hormonal contraceptives on microbiome composition, the research team observed synergistic effects between training and probiotic supplementation.
“Probiotic supplementation demonstrates promising ergogenic effects, particularly on aerobic capacity and recovery, although outcomes vary depending on the strain and protocol used,” Carlone noted. “Knowledge gaps remain regarding individual responses, sex differences and long-term adaptations.”
Targeted microbiome interventions
Researchers across studies noted the potential of targeted interventions to optimize beneficial bacterial species and microbial diversity for improved athletic performance.
Mixed probiotic formulations, sometimes combined with vitamin D3, have been associated with increases in VO₂ max, aerobic power, time to exhaustion, endurance capacity and improvements in muscle mass or strength depending on the specific strains used (e.g., L. plantarum TWK10, L. plantarum PS128, B. longum OLP-01, L. plantarum Tana). However, other studies show no significant effects, highlighting substantial methodological differences and strain-specific responses.
Probiotics appear more consistently beneficial for immune function and recovery, particularly in endurance athletes, with reductions in pro-inflammatory markers and fewer upper respiratory tract infections. Gastrointestinal symptoms, which are common in endurance sports, may also be reduced by some multi-strain formulations though evidence is mixed.
“In endurance sports, probiotic supplementation appears to positively influence lipid metabolites, including SCFAs, modulate VO2 max and improve exercise duration, while in sports characterized by intermittent exercise, probiotics may reduce inflammatory process activity and improve factors related to psychological stress, such as anxiety and depression,” Carlone et al. wrote.
At the Wyss Institute at Harvard University, researchers studying the microbiomes of the 2015 Boston Marathon runners identified significant increase in the abundance of Veillonella and Prevotella species post-race, which they associated with lactate metabolism and energy substrate utilization. The proof-of-concept findings, published in Nature Medicine, also showed that the same strain increased the running performance of mice on a treadmill by 13%.
This research spun out into the founding of FitBiomics, a startup whose mission is to mine the elite athlete microbiome for novel probiotic strains that can transfer benefits to the general population. The company has since commercialized Nella, a combination of three athlete-derived probiotic strains for sleep, digestion and energy, and V•Nella that specifically targets fatigue with lactic acid metabolizer Veillonella atypica.
“Ultimately, FitBiomics aims to mine the biology of the most fit and healthy people in the world, then translate that information into consumer products to promote health and wellness to the masses,” Jonathan Scheiman, CEO and co-founder of FitBiomics, shared in a university press release shortly after the company’s founding in 2019. He is also co-author on the foundational Wyss Institute research, and follow-up studies continue to substantiate benefits.
Most recently, FitBiomics evaluated the effects of Nella (Lactobacillus acidophilus FB0012, Lactiplantibacillus plantarum FB0015 and Lacticaseibacillus rhamnosus FB0047) supplementation in 11 professional Italian soccer players from the Palermo Football Club for 24 weeks. The study was carried during the competitive season, when heavy training and frequent matches can compromise recovery, energy levels and sleep quality, and when performance ultimately determines championship or relegation outcomes.
Findings demonstrated a 69% increase in sleep quality, a 31% increase in energy levels and a 37% improvement gut health (bowel movements) compared to placebo. Further mechanistic analysis showed a decrease in oxidative-stress markers and a higher free-testosterone-to-cortisol ratio, which the researchers reported suggests a shift toward a more favorable anabolic and recovery state.
“We hypothesize that these exercise-adapted lactobacilli harbor genomic adaptations that contribute to the significant improvements observed in sleep quality, general health and energy levels after intervention,” the research team, led by Tindaro Bongiovanni, head of performance at the Palermo Football Club, wrote. “Moreover, the exercise-adapted microbiome more generally may be responsible for the health improvements conferred by exercise, including sleep quality.”
Ralf Jäger, PhD, researcher and managing member of consulting firm Increnovo who was both co-author on the 2020 International Society of Sports Nutrition athletic gut microbiota review and the Italian soccer study, notes that benefits are species specific. He also led one of the first probiotic sports performance studies which showed improved recovery and performance following exercise-induced muscle damage with anti-inflammatory strains from Italian biotic supplier Probiotical.
“If there is one overarching takeaway, it is that the gut microbiome should no longer be viewed as a passive bystander in sport, but as an active, trainable system that interacts with exercise, nutrition, recovery and even mental resilience,” Dr. Jäger said.
“We are only at the beginning of translating this biology into practical performance strategies, but the potential for safe, personalized, microbiome-based ergogenic support is enormous.”
He noted the need for large, well-controlled in-season trials linking specific microbial shifts to objective performance, recovery and injury-risk markers and that routine integration of a more personalized, microbiome-driven approach could transform optimization of sport-specific athletic performance.
Source: Frontiers in Nutrition. doi: 10.3389/fspor.2025.1641923. “The performance gut: a key to optimizing performance in high-level athletes: a systematic scoping review”. Authors: Junior Carlone, Attilio Parisi and Alessio Fasano.
