Elite Athletes Have a Surprisingly Different Gut Microbiome – And It Shifts With Age

Training for elite sport rewires the body in ways that are obvious on the track or in the pool. What is less obvious is what happens inside the gut. A new dataset and analysis from Claudia Lenz and colleagues, published on Zenodo and archived under NCBI BioProject PRJNA1259926, compared the gut microbiomes of 148 German junior and senior elite athletes against 108 healthy adult controls. The results are early and preliminary, but they raise pointed questions about how training load, age, and diet intersect to shape the microbial communities living in an athlete's intestine.

Junior and Senior Athletes Show Opposite Diversity Patterns

The headline finding is a split between age groups that runs counter to a simple "athletes are healthier, therefore more diverse" assumption. Junior athletes showed lower microbial evenness and diversity than healthy adults. Senior athletes, by contrast, displayed higher microbial richness than the control group. Both groups clustered separately from healthy adults in principal coordinate analysis, meaning the composition of their gut communities was statistically distinct, not just noisier.

Lower diversity in junior athletes is counterintuitive given that unique athlete gut microbiome profiles are often described as metabolically advantageous compared to sedentary populations. One plausible explanation is that junior athletes are still in a developmental phase, with intense early training imposing physiological stress that temporarily narrows the microbial community before it reorganizes. Senior athletes, who have accumulated years of training adaptation, may arrive at a broader and more resilient microbial landscape. That interpretation is speculative, though; the study's cross-sectional design cannot confirm it.

Specific Gut Bacteria Enriched in Elite Athletic Populations

Beyond diversity metrics, the team used LEfSe (Linear Discriminant Analysis Effect Size) to pinpoint taxa that were enriched in athletes relative to controls. One notable finding was the enrichment of Escherichia-Shigella in the athlete group. This genus includes both harmless commensal strains and well-known pathogens, so its enrichment is not straightforwardly good or bad; context matters enormously. The finding does, however, suggest that the athlete gut is not simply a "healthier" version of the non-athlete gut – it is a functionally different environment shaped by repeated exertion, specific nutritional demands, and likely altered intestinal transit times.

Research on other athlete-associated taxa has found microbes like Veillonella linked to endurance metrics. Studies on Veillonella and endurance performance suggest this bacterium converts lactate into propionate, a short-chain fatty acid that may fuel sustained effort. Whether the German cohort showed similar enrichment is not detailed in the available data summary, but the broader point stands: particular microbes appear repeatedly in high-level athletic populations, hinting at functional roles worth investigating.

How the Team Controlled for Confounding Factors

One of the study's methodological strengths is its matched-subgroup analysis. When comparing adult athletes to healthy adult controls, the researchers controlled for age, sex, body mass index, and dietary pattern. That last variable is especially important: elite athletes notoriously eat differently from the general population, consuming more protein and total calories, and diet is one of the strongest known drivers of gut microbiome composition. By matching on dietary pattern, the team attempted to isolate signals attributable to athletic status itself rather than to what athletes eat.

The analysis used 16S rRNA sequencing for taxonomic profiling and PICRUSt2 for functional prediction. As noted in methodological critiques of microbiome sequencing approaches, 16S metabarcoding provides a broad taxonomic picture but cannot resolve species-level distinctions with the precision of shotgun metagenomics. PICRUSt2's functional predictions are inferences from taxonomy, not direct measurements of metabolic activity. These are standard tools for this type of research, but they set a ceiling on what conclusions can be drawn.

Open Questions About Causality and Sample Scope

Because this is a cross-sectional observational study, causality cannot be established. It is impossible to tell whether elite training produces the observed microbiome signatures, whether people with certain gut profiles are more likely to reach elite level, or whether some third factor drives both. The cohort is also geographically and culturally specific: 148 German athletes, trained in a particular sporting system, eating within a broadly German dietary context. Generalizing to athletes from other countries, sports cultures, or dietary traditions requires caution.

The functional predictions add an intriguing layer. PICRUSt2 analysis flagged differences in pathways for amino acid metabolism, glycolysis, fatty acid beta-oxidation, and quinone biosynthesis between athletes and controls. These are pathways with direct relevance to energy production and recovery, but predicted functional potential is not the same as measured metabolic output. Future work pairing microbiome sequencing with metabolomics or direct measurement of short-chain fatty acid concentrations would sharpen the picture considerably.

Where This Research Could Lead for Sports Nutrition

The most immediate practical thread is whether these findings can inform targeted interventions. If specific taxa or metabolic pathways are reliably associated with athletic performance, there is a plausible route toward microbiome-based nutrition strategies. Evidence already suggests that probiotic interventions can reduce gastrointestinal discomfort and support immune health in athletes, with some multi-strain blends linked to improved endurance and reduced fatigue. Whether supplementation could recreate or amplify the senior athlete microbiome pattern in junior athletes remains entirely untested.

For now, the Lenz et al. dataset, made openly available through NCBI BioProject PRJNA1259926, gives other researchers a resource to probe further. The age-dependent divergence in diversity, the enrichment of specific taxa under controlled dietary matching, and the predicted functional pathway differences collectively suggest that elite athletic training leaves a legible signature in the gut. Decoding what that signature means for performance, recovery, and long-term health is the work still ahead.

Evidence rating

INVESTIGATIONAL — 76/100

Caveats:

• Observational design — this study identifies associations, not causal relationships; it cannot determine whether training shapes the microbiome or whether microbiome composition influences athletic performance.
• Functional pathway data are computationally predicted (PICRUSt2), not measured directly from metagenomics, so metabolic conclusions are inferential.
• Published as a data repository preprint on Zenodo; full peer-reviewed publication is pending, and findings have not yet been independently replicated.
• Funding source was not disclosed by the authors.

Cross-sectional observational study comparing gut microbiome composition in 148 elite German athletes and 108 healthy adults, with matched-subgroup controls for key confounders. Demonstrates taxonomic and predicted functional associations with athletic status, but cannot establish causation. Functional pathway findings rely on computational prediction (PICRUSt2) rather than direct metagenomic measurement, and the work has not yet undergone full peer review or independent replication.

References

1. Claudia Lenz et al. (2026). Data for: Signatures in the Gut Microbiome of German Elite Athletes: Insights from a Matched-Subgroup Analysis. Zenodo (CERN European Organization for Nuclear Research). https://doi.org/10.5281/zenodo.20640491
2. Junior Carlone, Attilio Parisi, Alessio Fasano (2025). The performance gut: a key to optimizing performance in high-level athletes: a systematic scoping review. Frontiers in Sports and Active Living. https://doi.org/10.3389/fspor.2025.1641923
3. Zhiwei Li, Youqiang Li, Yufei Wang, Jinjin Chen, Yilan Liu (2025). The Athlete Gut Microbiome: A Narrative Review of Multi-Omics Insights and Next-Generation Probiotic Strategies. Nutrients. https://doi.org/10.3390/nu17203260
4. Junior Carlone, Ághata Cardoso da Silva Ribeiro, Attilio Parisi, Saverio Giampaoli, Alessio Fasano (2026). Profiling the Athletes’ Gut Microbiome: A Critical Methodological Perspective on 16S Metabarcoding and Shotgun Metagenomics. Biology. https://doi.org/10.3390/biology15080600
5. Kinga Zielińska, Paweł P Łabaj, Kinga Humińska-Lisowska (2025). Unique Athletic Gut Microbiomes and Their Role in Sports Performance: A Narrative Review. Journal of Human Kinetics. https://doi.org/10.5114/jhk/202642