Gut Health, Diet, and Performance – New Research Shows How Microbiota Affects Athletes

Summary in 7 seconds instead of 7 minutes: A new overview article — “Dietary Patterns, Gut Microbiota and Sports Performance in Athletes: A Narrative Review” — compiles current research on the connection between athletic performance, dietary habits, and gut health—specifically the bacterial composition in the gut, known as the gut microbiota, revealing a deeper link than previously understood. The article suggests that athletes often have more diverse gut microbiota, which can correlate with better metabolic health and recovery. Training, energy requirements, and dietary habits influence the gut microbiota, which in turn impacts both immune function and performance. The research indicates that a balanced, fiber-rich diet is beneficial for both the gut and muscles, yet more studies are needed to fully understand how various dietary patterns affect the gut's role in sports performance.

Gut Microbiota in Athletes

Research indicates that elite athletes tend to have more diverse gut microbiota—meaning they possess a greater variety of bacterial strains—compared to non-athletes, regardless of Body Mass Index (BMI). Our guts host between 100 and 1000 trillion bacteria (up to 1 quadrillion), spread across roughly 2000 known species. Because bacteria do not flourish in acidic environments, fewer are found in the stomach, but many more exist further along the gut where the pH is higher. 

These bacteria are vital for several functions: they help maintain the normal function of gut epithelial cells, produce short-chain fatty acids that impact metabolic status, and are key players in the immune system. An imbalance in microbiota can detrimentally affect multiple systems at once and has been linked to increased risks of diabetes, cardiovascular diseases, fatty liver, overweight, and gut diseases like IBS (Irritable Bowel Syndrome). 

Training and Microbial Diversity

Studies show that athletes have microbiota comprising 22 bacterial strains, while non-athletes have fewer: non-overweight individuals around 11 strains and overweight individuals about 9. This suggests that physical activity can enhance a healthier and more varied microbiota. Notably, higher levels of Akkermansia muciniphila, a bacterium associated with better metabolic health, were often found in athletes and individuals with a lower BMI.

A plausible reason athletes have greater diversity is that they consume more food. Higher energy intake typically entails more protein, fiber, carbohydrates, and vegetables—in short, more of everything to meet their energy needs. In one study, individuals training at least 11 hours per week had a more diversified microbiota than those training less. This supports the hypothesis that increased training and energy intake leads to richer microbiota. 

Additionally, a study revealed that competitive cyclists exhibited a decreased relative abundance of Bacteroides spp. Furthermore, the relative abundance of Prevotella spp. was higher in cyclists who trained more than 11 hours per week compared to those who trained less. These findings provide evidence supporting the idea that physical exercise can induce changes in the composition of the gut microbiota.

Does the type of training matter? Strength training vs endurance?

Studies have investigated how specific training interventions, such as endurance training and strength training, affect the microbiota. The results suggest that endurance training can increase the presence of certain microbes like Verrucomicrobia and Akkermansia, which are associated with improved health. In these studies, there were no significant changes in total energy intake or macronutrient distribution (carbohydrates, fat, protein) after training, but changes in the composition of the microbiota were observed. For strength training, however, no clear effects were reported in those studies.

The impact of gut microbiota on sports performance

The relationship between gut microbiota and sports performance is complex and influenced by genetic, environmental, and nutritional factors. Animal experiments show that a well-balanced gut microbiota can improve endurance, while the absence of microbiota can impair performance. Probiotic supplements have also been studied in relation to athlete health and performance, but results are mixed so far and do not allow for definitive conclusions. However, there are review articles showing that the intake of probiotic beverages is linked to fewer gastrointestinal discomforts and a lower incidence of upper respiratory infections, such as cough, cold, and other cold symptoms.

The authors demonstrated that the administration of probiotics might reduce symptoms of gastrointestinal and upper respiratory tract illnesses, enhance physical performance, improve post-exercise recovery, and improve mood-related outcomes. Therefore, there exists a significant association between the composition of the gut microbiota and sports performance.

The Impact of Diet on Gut Microbiota

Vegetarian, meat-based, and balanced dietary patterns influence the microbiota in different ways. Changes can occur quickly after a diet change and often revert back to baseline shortly after the new diet stops (usually within 24–48 hours). Both the quality and quantity of consumed macronutrients and the type of diet have a significant impact on the composition and function of the microbiota. Several studies show differences in gut microbiota profiles between athletes and non-athletic individuals and attempt to link these differences to diet and performance.

Here is an overview of the key evidence regarding different dietary patterns and their impact on athletic performance.

• High-Carbohydrate Diet is not really a standalone dietary pattern but rather a tool to meet athletes' energy needs. Therefore, studies often don’t isolate "high-carbohydrate diet" against the microbiota. Athletes are advised to prioritize simple carbohydrates to maintain glucose homeostasis and limit fiber intake before training since this reduces the risk of gastrointestinal issues — classic advice from us that you've surely heard 100 times. A high intake of fast carbohydrates can improve performance during training or competition, but too little fiber over time can decrease short-chain fatty acid (SCFA) production, thereby negatively affecting gut health. Conclusion: eat real food, not just sports drinks. If over 50% of your energy intake over time comes from sports drinks and gels, you should review your diet. 😀

• Ketogenic Diet comes in many variations, but the common factor is that fat is the main energy source. A high intake of saturated fat, however, can increase inflammation and insulin resistance. Increased intake of polyunsaturated fats is discussed as a healthier alternative.

• High-Protein Diets have been studied for their effects on the microbiota and its protein metabolism, which in some cases can reduce inflammation and support muscle recovery. At the same time, it's unclear where the limit goes for when protein intake becomes too high. An excessively high intake can inhibit bacteria that ferment carbohydrates and instead favor the formation of undesirable metabolites, such as ammonia.

  Studies show mixed results: some report reduced levels of SCFA-producing bacteria in athletes on a high-protein diet, while others find increased microbial diversity. Here fiber intake stands out as a key factor – sufficient dietary fiber contributes to a stable microbiota and supports the production of short-chain fatty acids.

• Plant-Based Diet and Mediterranean Diet are highlighted for their high fiber content, which benefits a healthy microbiota and can improve metabolic functions, such as fat oxidation. In a study of 258 individuals divided into four groups (Western diet, flexitarians who ate meat 1–2 times per week, vegetarians, and vegans), differences in gut microbiota were observed between the groups. In general, vegans had the most "healthy" gut profile, followed by vegetarians, flexitarians, and finally individuals on a Western diet rich in salt, sugar, and saturated fat.

Conclusion: Variety is Key

This overview highlights the central role of gut microbiota for both health and athletic performance. However, how different dietary patterns affect the gut microbiota and thus athletic performance needs to be further explored before we can draw definite conclusions.

A fairly good summary is that a balanced mixed diet with plenty of fruits and vegetables, fibers, and sufficient energy is best for the gut and muscles. Strive for variety and avoid unnecessary exclusions. If anything, you might reduce red meat, sugar, salt, and saturated fat — but that's advice probably not missed by anyone.

A final note: do not optimize your diet solely for the gut's sake. Think about the whole picture: eat enough calories, have a high carbohydrate intake, and moderate protein intake for good recovery and fresh muscles. Eat your vegetables, fruits, berries, and nuts, and your gut will probably be fine. The best thing about the gut is that it quickly tells you if something is wrong. 🙂