Researchers Núria Mach from the Open University of Catalonia and Dolors Fuster-Botella of the University of Paris-Saclay reviewed a total of 28 studies published since 2007 for “greater understanding of how the gut microbiota may exert beneficial effects on elite athletes.”
“Understanding the effect of exercise on gut microbiota composition and structure is still in its infancy and the function of microbiota on exercise adaptation remains unknown,” they wrote in their review, which at the moment is still an uncorrected proof, slated to publish in the next edition of The Journal of Sport Health Science.
Focusing specifically on endurance, the researchers found that results of past studies suggest how gut microbiota ferment complex dietary polysaccharides into small chain fatty acids to be used as energy sources “and improve endurance performance by maintaining glycemia over time.”
Relationship between gut microbiota and exercise performance
According to the researchers, the studies reviewed can be divided into two main groups: Studies that explore the relationship between gut microbiota and exercise performance, and studies that explore the effect of probiotics and prebiotics in trained individuals.
From the first category, most were conducted on mice and rats, and only two of the 10 were human studies. This included a 2014 study out of the University College Cork in Ireland by Clarke et al, which looked at male professional rugby players. A study highlight was that “athletes have a greater gut microbial diversity compared to sedentary individuals.”
The meta-analysis researchers point out that the rugby study’s confounding effect is that “athletes ate more calories, fat, carbohydrates, sugars, protein, protein supplements, and saturated fat per day than the controls—therefore it Is difficult to draw conclusions form the study. [and] assess the impact diet has on gut microbial diversity and exercise performance.”
But the other human study report used in the review supports the study of Clarke et al. It analyzed 1493 participants of the crowdsourced American Gut Project. Here, researcher Robert McFadzean of the University of Colorado Boulder found that exercise can help modulate human gut microbiota, and participants who exercised more frequently had increased microbiota diversity.
Probiotics and prebiotics for endurance athletes?
The second group of studies analyzed, totaling to 18 studies, suggest that probiotics may help with endurance exercise.
Though the researchers noted that the articles reviewed don’t specifically identify an ergogenic role of probiotic therapy, the studies show signs of how probiotics enhance immune function, neutralize reactive oxygen, and normalize gut mucosa permeability, “which might improve performance in athletes undergoing intense physical training. Thus, probiotic supplementation could act as an indirect ergogenic aid.”
Mach and Fuster-Botella point to the design flaws of the studies they reviewed. “Dose–response experimental studies of probiotic supplementation should investigate parallel changes in exercise outcome, clinical outcome, immune function as well as dietary and exercise regime over a period of several weeks to a few months,” they wrote.
A call for more studies
Mach and Fuster-Botella call for “more well-designed studies of probiotic supplementation in various athlete groups [to] understand the complex relationship between diet, activity levels, clinical outcome, and gut microbiota modifications caused by probiotic supplementation.”
According to the two researchers, the reviewed studies suggest that administering different Lactobacillus and Bifidobacterium strains may “help maintain a state of general health, enhance immune function, improve gut mucosal permeability, reduce oxidative stress, and obtain energy from plant-carbohydrate sources.”
But they also press the need for future studies to “tease apart the respective influences that high intensity exercise and the intestinal microbiota have on the immune, redox system, and energy metabolism and to track the impact that ongoing functional foods have on intestinal microbiota.”
Source: Journal of Sport Health Science
In Press, Uncorrected Proof, doi:10.1016/j.jshs.2016.05.001
Title: Endurance exercise and gut microbiota: A review
Authors: Núria Mach, Dolors Fuster-Botella