Gut Microbiome in Athletes

The relationship between athletic performance and the gut microbiome has been a key research interest in recent years. Studies have indicated differences between the gut microbiota of athletes and non-athletes, suggesting an influence of exercise on the gut microbiome. Evidence has also emerged connecting the presence of certain microbial organisms in the large intestine with athletic performance. Although the mechanisms behind this relationship are still poorly understood, it provides a potential method for improving athletes’ health and physical condition in the future.

What is the Gut Microbiome?

According to Harvard Health, the gut microbiome is a network of trillions of organisms, including bacteria, archaea, fungi, parasites, and viruses, that exist within the human digestive tract. The largest number of gut microbiota are located within the small and large intestines, although they are present throughout the body. Some even label the gut microbiome as an organ in and of itself because of its important functions in nutrient absorption, immune system modulation, vitamin metabolism, mood regulation, and production of important metabolic compounds.

Research suggests that the gut microbiome is unique in each individual and is influenced by genetic factors. Initial exposure to microorganisms occurs during infancy, beginning when a baby is delivered. A mother’s microbiota greatly influence a child in early development through breastfeeding as well. Both genetic makeup and exposure to certain organisms in infancy affect a person’s final gut microbiome composition and therefore can increase or decrease one’s predisposition to disease.

In a healthy person, the microorganisms of the gut exist in a symbiotic relationship. The thousands of species of organisms work together to maintain smooth operation of the body’s metabolic, hormonal, and immune processes. Factors such as age, infectious disease, prolonged antibiotic use, and diet can cause disturbances in this balance, leading to multisystem consequences. The plasticity of the human gut microbiome and its ability to affect overall health through changes in its composition make it a potential target for improving both wellness and performance.

Physical Activity and the Gut Microbiome

Exercise has been found to have a bidirectional effect on the gut microbiome. In the figure shown below, this relationship is “J-shaped,” with deleterious effects occurring in sedentary individuals but also in intense exercise. Interestingly, the negative effects of extremely intense exercise on the gut microbiome are greater than the negative effects of sedentary lifestyle. However, optimal levels of exercise can positively impact gut microbiome diversity and increase the presence of beneficial organisms. More specifically, average exercise intensity and regularity augments the amount of short-chain fatty acids (SCFAs) present in the gut, which increase metabolic efficiency and improve immune function.

(O’Brien et al., 2022)

Notably, endurance athletes often experience GI symptoms and upper respiratory infections during or after exercise. These symptoms can have negative effects on performance in competition and are attributed to diversion of blood supply from the gut during prolonged, intense physical activity. This phenomenon is called gut ischemia and is more severe during dehydration. Although this topic is still understudied, supplementation with probiotics before races or games has been shown to protect against gut ischemia-related symptoms. These observations show promise for a role in gut microbiome-related interventions in improving athletic performance and health.

Gut Microbiome and Performance Metrics

Not only can probiotic supplementation alleviate GI and upper respiratory symptoms that inhibit performance in endurance athletes, but it can also improve performance in athletes without these symptoms. For example, Veillonella atypica is an organism found in stool samples of marathon runners. When compared to a control, V. atypica supplementation significantly improved treadmill performance in mice.

Lactobacillus plantarum, a bacterium found in cabbage, has been shown to increase grip strength and swim to exhaustion time in mice, as well as causing decreased lactic acid buildup. Lactobacillus supplementation also reduces muscle atrophy, which may explain its performance-enhancing effects.

Lactobacillus plays a role in alleviating immunosuppression in athletes as well, which leads to a reduction in upper respiratory tract infections. Evidently, Lactobacillus is a powerful, health-promoting organism that can improve athletic performance. Conveniently, it is found in fermented foods, which eliminates the need for supplementation. Consumption of fermented foods has been associated with increased SCFAs and health-promoting bacteria, along with decreased pathogenic bacteria in the gut, including Escherichia coli. Although there is currently little research exploring the impacts of fermented food consumption on athletes specifically, these conclusions show promise in fermented foods as a potential method to improve gut health and performance.

Athletic Diet and the Gut Microbiome

In addition to exercise, sport-specific diets also have an impact on the composition of the gut microbiome in athletes. A 2020 review showed the impact of diet on the levels of specific organisms in the gut microbiomes of various types of athletes. More specifically, plant and fiber-rich diets were associated with increased presence of Prevotella, which increases efficiency of amino acid and carbohydrate metabolism.

Experiments with mice fed a low-carbohydrate, ketogenic diet showed increased levels of Akkermansia muciniphila, an organism that controls inflammation and gut barrier function. A. muciniphila also improved metabolic efficiency in mice fed high-quality whey protein. In contrast, mice taking antibiotics experienced less muscle gain, indicating that the gut microbiome may play a role in muscle anabolism.

Summary

Although its mechanisms of action are poorly understood, the gut microbiome has tremendous untapped potential for positively affecting both general health and athletic performance. Improving the balance of gut microorganisms through moderate exercise, diet, and supplementation can lead to better immune function and more efficient metabolism. In athletes specifically, increasing beneficial organisms and decreasing pathogenic organisms in the gut can provide a competitive edge, both through reduction of GI and respiratory systems and through improved metabolic function.