The Microbiome and Athletic Performance

Gut microbes play a big role in athletics, and the microbiome could be positively impacted by behavior changes and supplements. Let’s dive into some smelly science.

Photo: Getty Images

Heading out the door? Read this article on the new Outside+ app available now on iOS devices for members! Download the app.

In 2017, my co-coach Megan and I got curious about the microbiome after having lunch with an investor in a start-up that did mail-in gut biota testing. The next morning, we read the instructions on the mail-in kit. 

“Easy enough,” we thought. “Brew the coffee strong and let’s fulfill our scientific duties.”

We forgot about the testing after a while. Even the unfortunate memories of what we had to do with that Q-tip faded away. Then one day a couple months later, we got a return-to-sender for that shipment. Yes, we got our now-fermenting samples mailed back to us. You don’t know true rejection until you receive an 8-week-old vial of your own poop.

We never got our microbiomes tested, feeling like the science was a bit uncertain. But the field has exploded in the last few years, and it’s a great time to look at emerging studies connecting gut microbes and athletic performance. Eat some prunes and get those samples ready, because it’s a fascinating field.

Microbiome Function

A 2020 review article in the Journal of the International Society of Sports Nutrition provided a great intro to the complexity of gut microbiota in athletes. The microbiome consists of thousands of bacterial groups, millions of genes, and non-bacterial cells and viruses. They act together like the New Englands Patriots’ dynasty–the exact players shift over time, but they remain full of crap. In addition to bowel movements, the microbiome is essential for “nutrient uptake, vitamin synthesis, energy harvest, inflammatory modulation, and host immune response.” There are studies where mice are conditioned to have a limited microbiome, resulting in terrible health issues, only to be rescued when the microbiome is restored.

The ever-evolving microbiome is influenced by genetics, environment and behavior, including athletics. The athletic influence on the gut is fascinating to researchers because of the extreme demands placed on metabolic processes. Just imagine the strain put on the microbiome during an ultramarathon, as an athlete consumes thousands of calories under major stress. Talk about a pressure cooker to force constant adaptation, particularly in cells and bacteria that have rapid turnover! 

RELATED: What’s Causing Your Stomach Problems On Runs?

And it’s not just direct metabolic adaptations. Other studies find that the microbiome may influence everything from the immune system to the aerobic system to the endocrine system to the nervous system to 2000s heavy metal band System of A Down, etc. 

Put these elements together and you have the perfect storm of scientific opportunity. Thousands of variables with massive cross-population differences; an emerging understanding of interrelated physiological functions of those variables; and aggregation of health outcomes that can be correlated with individual variance–it’s overwhelmingly exciting, but also complex. 

There’s a chance for astounding amounts of statistical noise (our confounding variables will blot out the sun!), but with recent advances in sequencing and analysis, also the potential for scientific breakthroughs. Could it reshape how we think of athletic performance too?

The jury is out, but I bet that in 20 years, we’re all checking in on our gut microbiome. Invest in Q-Tips.

Microbiome Variance

Current research is moving toward a general understanding of how the microbiome varies for different subpopulations. A 2017 study in PLoS One found less diversity of biota in sedentary premenopausal women, which is a negative adaptation in most cases. A 2019 study in BMJ Open found much higher biota diversity in professional rugby players than the general population. Many of the biota were associated with metabolism of amino acids and carbohydrates.

A 2016 study found that VO2 max alone explained 20% of variation in species count in the microbiome, likely showing some connection between cardiovascular fitness and gut biota. As we train our bodies, we may be training our bacteria. Across athletes, the type of sport can influence the microbiome, with a 2017 study finding that bodybuilders and endurance runners varied substantially, possibly related to different nutrition strategies. 

Beyond biota diversity, studies are finding some indicator organisms that may be especially important for peak athletic performance. A 2017 study in Microbiome looked at elite and amateur cyclists, finding no significant difference in diversity, but a greater abundance of the genus Prevotella. That sounds like a delicious cheese but is actually an organism commonly found in non-Western populations. (Maybe it can be cheese too, I want every microscopic organism to believe in its dreams). One of its roles: carbohydrate and amino acid metabolism, which could directly impact performance and adaptation. Every year, new organisms are being highlighted as beneficial or detrimental for health and performance.

Athletes seem to have beneficial adaptations for metabolism of complex carbohydrates (2012 review), and likely other nutrients too. That translates to dozens of specific organisms that are likely to be found in higher proportions in athletes, from our cheese friend Prevotella to A. muciniphilia, the absence of which is correlated with increased obesity in mice, and may be related to gut inflammation. But that underscores the difficulty of this research–when there are thousands of variables that all work together and separately, isolating cause-and-effect can be immensely challenging. 

Add to that another problem: biota can vary in acute ways, like in this 2014 study in Genome Biology that found variation before and after a half marathon race, or this 2021 article in Frontiers of Nutrition that reviewed how intense exercise could damage the intestinal wall in some cases.

RELATED: Beating Gut Problems In The Heat

Microbiome Interventions

The big question is how can knowledge of the microbiome influence individual interventions? Personally, I got 99 problems and my crappy GI system is related to 98 of them, so I could use some guidance. There is not yet a measurement-and-intervention protocol that is agreed upon. A 2019 study in Nature found a post-marathon spike in Veillonella, which is known to metabolize lactate. After isolating Veillonella in a runner, the researchers inoculated mice with it, and those mice were able to run 13% farther on their adorable mice treadmills. The lead author of that study founded a company called Fitbiomics (see this Nature article), which aims to isolate what makes the world’s best athletes unique, then apply that information to develop nutrition interventions for everyone. Capitalism!

A 2019 review in the Journal of the International Society of Sports Nutrition looked at the current science of probiotics, finding some potential benefit, but limited certainty. That’s backed up by a 2020 review in Nutrients on probiotics and athletic performance, which found potential benefit but cautioned that more studies are needed. 

The pill (or injection) that solves our GI woes while improving our athletic performance, immune function, and overall health (or based on this 2020 study, possibly even sexual function!) may be coming at some point, but whether that’s in 5 years or 50 years is uncertain. Personally, I have found some benefit with a top-rated probiotic, though that is exceedingly anecdotal and I was also starting at “atrociously terrible,” so I could probably swallow hand soap and see some improvement. 

Next Steps

In the future, it’s likely that the scientific community will develop a detailed understanding of how the microbiome functions, much like the human genome was unraveled with DNA sequencing technology. We’ll be able to see not just our levels of each type of bacteria, but how that relates to function, and how we can make long-term changes with behavior modifications (and if needed, with medication). If I had to start over as a researcher, I think I’d go into this field–so much potential, so many lives that can be changed, so many poop jokes.

For now, though, we know that the microbiome is really, really important, and that being an athlete seems to help biota diversity and function. Eat well, ideally whole foods. Exercise enough, but don’t go so hard that you’re mailing a sample of blood to a microbiome start-up. Consider a probiotic, but only on the recommendation of a doctor or nutrition professional, and make sure it’s well-researched.

And most of all, stay tuned. Our understanding of the microbiome is expanding by the day, and I will be waiting on the edge of my toilet seat for new studies.

David Roche partners with runners of all abilities through his coaching service, Some Work, All Play. With Megan Roche, M.D., he hosts the Some Work, All Play podcast on running (and other things), and they wrote a book called The Happy Runner.

Want to Know What It Takes to Finish at Western States? Just Ask Hellah Sidibe.

Find out what happened when this six-year run streaker and HOKA Global Athlete Ambassador took on an iconic ultramarathon in California's Sierra Nevada