A special gut microbe helped mice get jacked, researchers found. Because this microbe is found in humans, it raises the possibility that it could help us get stronger, too.
For now, that remains unproven. But the work, a new study in the journal Gut, provides a compelling case for creating a probiotic that can help with maintaining strength and fitness as we age, the researchers argue, or combat muscle-wasting disorders.
“Taken together, our findings provide solid evidence confirming the existence of an gut-muscle axis in which this identified bacterium positively modulates muscle metabolism and muscle strength,” said coauthor Jonatan Ruiz, a professor in the Department of Physical Education and Sport at the University of Granada, in a statement about the work.
Until now, the connection between muscle strength and gut microbiota was unclear, even though it’s well established that these bacteria influence our bodies in other ways, such as metabolism and cardiovascular health.
The researchers began by exploring if there was a connection between certain gut microbes and muscle strength. Using stool samples, they analyzed the microbiomes of 90 young adults between 18 and 25 years old, as well as 33 older adults between 65 and 75 years old. They also measured the grip strengths of the participants using a handgrip test.
The efforts revealed an interesting correlation. Participants with higher grip strength also had greater quantities of a genus of gut bacteria called Roseburia, and in particular a species called Roseburia inulinivorans. Older adults that possessed the bacterium demonstrated 29 percent greater grip strength in the tests compared to those that didn’t. In addition to the strength benefits, younger adults with the bacterium showed higher cardiorespiratory capacity. On the flip side, older adults had low levels of Roseburia inulinivorans, perhaps adding to the picture of why we lose strength and muscle mass as we grow older.
To explore if Roseburia was directly responsible for the strength gains, the researchers conducted follow-up experiments with mice. Mice which had Roseburia inulinivorans introduced into their digestive systems showed on average a 30 percent bump to their grip strength in their forearms than the ones that didn’t.
Intriguingly, muscle composition also changed: the mice that received the microbes developed thicker muscle fibers a larger share of type II, or “fast twitch” muscle fibers, which your body uses to perform explosive and powerful movements. In other words: the kind of muscle that lifters chase after.
So, case closed? Will Roseburia inulinivorans supplements represent the new frontier in nerdy ways to get jacked?
Not quite. There’re several notable caveats to the study, beyond its relatively human small sample size. In the mice experiments, the human strains of the microbe didn’t permanently take hold in the intestine, and it’s unclear how the effects will hold up in the long-term. And of course, what seems to work for mice may not work for humans.
But if the findings hold up, it “opens up the possibility that the bacterium under investigation could be used as a probiotic to help preserve muscle strength during aging,” said study coauthor Borja Martínez Téllez, a researcher at the University of Almería, in the statement.
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