One difference between elite athletes and the rest of us might be in what hangs out in their guts.
Microbes that flourished in the guts of some runners after a marathon boosted the time that lab mice ran on a treadmill, researchers report June 24 in Nature Medicine. These particular microbes seem to take lactate, pumped out by muscles during exercise, and turn it into a compound that may help with endurance.
The study “adds to our understanding of how the bacteria in our gut may influence all sorts of different facets of health and disease,” says Kim Barrett, a gastrointestinal physiologist at the University of California, San Diego, who was not involved with the study. While most studies of the microbiome — the medley of microorganisms that live in and on the body — rely on correlation, this work shows that specific bacteria, as well as the products that they make, can improve athletic performance in mice, she says.
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In the study, researchers collected stool samples from 15 elite runners for five days before and after they ran in the 2015 Boston Marathon, and compared the samples’ microbial makeup with that of poop collected from 10 nonrunners. The runners’ samples showed a bump in the abundance of bacteria from the genus Veillonella after the race. The team also saw an increase in Veillonella in a group of 87 ultramarathoners and Olympic trial rowers after a workout.
This finding raised the question of whether these microbes were mere bystanders or were actually helping their hosts. So the researchers cultured one strain, Veillonella atypica, from a runner and fed it to mice. Not all of the 32 mice responded to the treatment, but on average, mice that received the microbes ran for 13 percent longer in experiments than mice in a control group.
The work shows that “a single bout of exercise can have effects on your microbiome,” says Jeffrey Woods, an exercise physiologist at the University of Illinois at Urbana-Champaign. But he is skeptical of whether the improvement in the mice’s stamina is important, noting that the mice were tested in a series of short runs that “isn’t anything like the marathon run.” The researchers might have found other microbes at play if more stool samples had been studied, he says.
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The authors, however, say that the microbes could boost athletic performance. In a race, “sometimes people worry about a fraction of a second … this could be much more than that,” says biotechnologist George Church at Harvard University.
Veillonella feast exclusively on lactate to get the carbon that they need to grow and, in the process, make propionate, a compound shown to raise heart rate and oxygen use in mice. Propionate may also boost humans’ metabolism. To test whether the molecule could be behind the improved performance, Church and his colleagues gave some of the mice a propionate enema. Those mice also increased their running times similarly to the mice fed the Veillonella.
The scientists also injected mice with lactate that they could track, and traced it to the gut wall. The lactate seems to help these microbes grow, says Laura McCabe, a physiologist at Michigan State University in East Lansing, who was not involved with the work. “It’s kind of cool, because it’s not your diet. Normally everybody thinks it’s what you eat that modifies the microbiota composition.”
It’s not clear whether these microbes bloom after exercise in the vast majority of people who aren’t elite athletes. “It may be something that the average person may not normally experience,” Church says. But probiotics — pills or food supplements that are supposed to contain helpful bacteria — may be able to bring these microbes to the masses.
Church and his colleagues intend to do a clinical trial to find out if the microbes actually benefit people. And several of the study authors are part of the company FitBiomics, which is exploring probiotic supplements, and have filed a patent application for ones that could include Veillonella and other possibly exercise-enhancing microbes.