Brazil Gut Bacteria Tied to 29% Greater Muscle Strength

A study published in Gut has identified a specific type of gut bacteria that is linked to greater muscle strength. Researchers found that older adults with detectable levels of Roseburia inulinivorans had 29% higher handgrip strength compared to those without the bacteria. In younger adults, higher levels of the same microbe were associated with stronger grip strength and better cardiorespiratory fitness.

The research analyzed stool samples from 90 healthy adults aged 18 to 25 and 33 older adults aged 65 and older. Participants completed handgrip strength tests, leg press and bench press assessments, and VO2 max testing. The goal was to see if any specific bacteria were consistently linked to stronger muscles or better performance.

Out of all the microbes detected, the genus Roseburia stood out. These bacteria are known for producing short-chain fatty acids in the gut. However, within that group, only Roseburia inulinivorans showed a clear connection to muscle strength. Other Roseburia species did not show the same pattern, suggesting that different bacteria within the same family may affect muscle health differently.

To explore whether the bacteria might cause changes in muscle performance, researchers ran a follow-up experiment in mice. After reducing the animals’ gut microbes with antibiotics, they introduced different Roseburia species into the mice’s microbiomes once per week for eight weeks.

Mice given R. inulinivorans developed about 30% greater grip strength compared to the control group. Their muscles also showed structural changes. The mice developed a greater proportion of type II muscle fibers, which are responsible for explosive movements like sprinting and jumping. Their muscle fibers were also larger overall. Researchers observed shifts in metabolic pathways involved in muscle energy production, suggesting the bacteria may influence how muscle tissue processes fuel.

The findings support the idea of a gut-muscle axis, where microbes in the digestive tract help regulate muscle metabolism and strength. However, the research is still early. The study shows strong associations but does not prove that increasing this bacteria directly boosts strength in humans. Long-term studies are still needed to determine whether higher levels of R. inulinivorans actively improve muscle function or simply reflect other healthy behaviors that support strength.

There are already several evidence-backed ways to support beneficial gut bacteria that may indirectly benefit muscle health. Eating more fiber-rich foods like oats, beans, lentils, onions, garlic, and asparagus helps feed microbes that produce beneficial compounds. Resistance training remains the most reliable way to maintain muscle mass and power. A varied diet rich in plants, fermented foods, and whole ingredients helps cultivate a more diverse gut microbiome.

Muscle strength has traditionally been viewed through the lens of workouts and nutrition. This new research suggests another key player may be involved: the microbes living in the gut. But this research does not replace the fundamentals like lifting, eating protein, and getting adequate recovery. It adds a layer to the conversation that is worth paying attention to. What you feed your gut may be shaping your muscle health in ways that show up at the cellular level long before you notice them in the weight room.