The gut microbiome is made up of billions of microbial cells. It plays an important role in modulating the immune system, digestion, vitamin absorption, mood regulation, and a series of other key functions related to health and athletic performance. In recent years, an increasing number of studies have focused on the interaction between the gut microbiome and sports performance.
It has long been observed that physical activity can have a significant positive impact on intestinal health and increases the diversity of the microbiome with good bacteria. The effect of exercise on intestinal health can vary depending on the intensity of the exercise. Thus, a moderate amount of exercise can have a positive effect on intestinal permeability and inflammation. Moderate physical activity can also improve the ratio between Bacteroides and Firmicutes, which can contribute to the maintenance of a healthy weight. On the other hand, intense and sustained exercise can have a deleterious effect. It is believed that the negative symptoms associated with strenuous exercise are mainly due to a redistribution of blood that causes a lack of blood flow to the intestines – known as intestinal ischemia – which in turn leads to increased gut inflammation and permeability.
It is well established that there are considerable differences in the composition and diversity of the gut microbiome between athletes and sedentary individuals, athletes tending to have higher levels of health-associated bacteria. It is important to consider that not all types of exercise are created equal, some studies suggesting that there are significant differences in the gut microbiome of athletes participating in different types of sports.
Researchers have been interested in whether the presence of certain intestinal bacteria could help improve athletic performance. For example, in one study, the bacterium species Veillonella atypica was noted to be highly enriched in fecal samples of marathon runners. In addition, the researchers noted that when they supplemented mice with the bacterium V. atypica isolated from the fecal samples of marathon runners, this significantly improved their performance on the treadmill when compared to the control group. One possible mechanism to explain this benefit would be that V. atypica could increase lactate turnover and thus decrease the accumulation of lactic acid in the muscles.
One way to modify the gut microbiome is via a probiotic supplements. These are defined as “live microorganisms which, when administered in adequate amounts, confer a health benefit on the host“. Studies have shown an increase in certain metrics of sports performance in animals and humans following treatment with probiotics. For example, one study found that a four-week supplementation with a mixed-strain probiotic delayed athletes’ fatigue time by an average of 16% in a treadmill test conducted in hot temperature conditions. Another study showed that when a particular species of probiotic, isolated from the gut microbiome of Olympic-level female weightlifters, was administered to mice over a four-week period, it significantly improved swimming time to exhaustion as well as grip strength.
Another method of influencing the microbiome is through the use of prebiotics, which are defined as “a substrate that is selectively utilized by host microorganisms conferring a health benefit“. This consists of dietary fiber that cannot be easily directly digested by humans and thus serves to feed certain bacteria in the intestines with a favorable effect on health. Research on the effects of prebiotics on athletic performance is rather limited and has so far largely focused on symbiotic supplements, which are a combination of probiotics and prebiotics.
Although there are currently no clear recommendations for microbiome modification treatments for athletes, it seems likely that there is a substantial amount of untapped potential with regard to the gut microbiome and sports performance.