Gut microbes associated with Mediterranean diet increase muscle strength in mice

People with strong muscles are more likely to have certain bacteria in their guts, and feeding mice this bacterial strain made them stronger, a new study has found.

The study authors say this microorganism could be part of probiotic supplements, which could increase muscle strength. However, this requires researchers to find a way to store it in tablets. Additionally, study lead author Borja Martínez Telles, a sports scientist at Leiden University in the Netherlands, said the microbe could serve as a drug to treat frailty in older adults, assuming it is found to safely increase muscle strength in future human clinical trials.

The gut microbiome is closely linked to many aspects of overall health, and previous research has linked a more diverse gut population to higher muscle mass and strength. Additionally, “there is preclinical evidence suggesting a link between certain gut bacteria and muscle weakness,” Matt Cook, a nutrition researcher at Australia’s La Trobe University who was not involved in the study, told Live Science in an email. However, it was unclear which species affected muscle tissue.

Article continues below

you may like

In the new study, published March 10 in the journal Gut, researchers looked for gut bacteria that correlate with muscle strength. They collected fecal samples from 90 young participants aged 18 to 25 and 33 older participants aged 65 to 71 and asked them to perform strength training.

Both groups were instructed to test their grip strength by holding a handheld device. The researchers found that participants in both age groups with stronger grip strength tended to have higher numbers of the bacterium Roseburia inulinivorans in their feces. This species helps digest fiber and typically colonizes the intestines of people who follow a Mediterranean diet high in fruits, vegetables, omega-3-rich fish, and extra virgin olive oil.

Young participants were also asked to perform leg press and bench press exercises. Participants who were able to lift a heavier load 10 times without failing had higher abundances of R inulinivoran and another related bacterial species living in their guts called Roseburia intestinalis compared to younger participants with lower muscle strength scores.

However, the association between higher abundance of these microorganisms and higher load-bearing capacity may be explained by other factors. For example, people who strength train may acquire more bacteria and lead an overall healthier lifestyle by eating foods that influence their gut microbiome. To determine whether R. inulinivorans could actually improve muscle strength, the researchers administered various Roseburia species to mice using feeding tubes.

Grip strength in mice was assessed using a miniature pull-up bar. Mice fed R. canulinivorans for 4 to 8 weeks had 30% higher grip strength than other mice. Although this bacterial species enhanced muscle strength, it did not correlate with muscle growth. Meanwhile, mice fed another related species called Roseburia fesis developed more muscle mass.

The researchers then aimed to understand how these bacteria were linked to the more powerful mice. Researchers found that R. inulinivorans causes changes in muscle structure. Muscles that were previously rich in type I (“slow-twitch”) fibers, which contribute to endurance exercises such as sprinting in mice and long-distance running in humans, have reshaped into type II (“fast-twitch”) fibers, which are the key to muscle strength.

“We were able to demonstrate for the first time that there is a direct relationship between certain bacteria and muscle strength,” Martínez Telles said.

What to read next

Although these findings are promising, Professor Cook pointed out that the mice’s gut microbiota were depleted with antibiotics before being fed the Roseburia seeds, so it is unclear whether this depletion affects muscle strength.

The researchers in this study filed a patent for the use of R. inulinivorans to increase muscle strength. They hope to develop probiotics that can improve performance in the gym, or, once there is encouraging clinical trial data about their safety and effectiveness, to use them as medicines to prevent the onset of frailty in older adults, Martínez Telles told Live Science. “This is not a substitute for athletic training,” he said. “It’s more of a complement.” Further research is needed to confirm that such pill-formed bacteria can remain in the human gut long enough to maintain muscle improvements.

It will still be many years before this bacterium is available for general use. “The problem with this bacterium is that it is completely anaerobic, meaning it dies after five seconds of exposure to oxygen,” said Professor Martínez Telles. He and his colleagues would need to develop an airtight pill that would have this kind of shelf life.

“Further studies in humans are needed to confirm these animal findings,” Professor Cook said, adding that further research would need to include supplementing humans with these bacteria and observing the effects on muscles and the safety of ingestion.

In the future, Professor Martínez Telles hopes to investigate whether other gut residents can have similar effects on physical performance, opening up the possibility of increasing physical fitness through the gut.