A new study published in the journal Gut has identified a specific type of gut bacteria that may be linked to greater muscle strength. Researchers found that older adults with detectable levels of the bacterium Roseburia inulinivorans had 29% higher handgrip strength compared to those without it.
The study analyzed stool samples from two groups: 90 healthy young adults between the ages of 18 and 25, and 33 older adults aged 65 and up. Researchers then measured physical fitness through handgrip strength tests, leg press and bench press assessments, and VO2 max testing, which measures how efficiently the body uses oxygen during exercise.
Among all the microbes detected, the Roseburia genus stood out. This group of bacteria is already known for producing beneficial short-chain fatty acids in the gut. However, one species in particular, Roseburia inulinivorans, drew the researchers’ attention. In younger adults, higher levels of this microbe were linked to both stronger grip strength and higher VO2 max. Other Roseburia species did not show the same pattern, suggesting different bacteria within the same family may influence muscle health in different ways.
To explore whether the bacteria might cause changes in muscle performance, researchers ran a follow-up experiment in mice. After temporarily reducing the animals’ gut microbes with antibiotics, scientists 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 with the control group. Their muscles also showed structural changes, including a greater proportion of type II (fast-twitch) 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. These findings support the idea of a “gut-muscle axis,” where microbes in the digestive tract help regulate muscle metabolism and strength.
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 evidence-backed ways to support beneficial gut bacteria that may indirectly benefit muscle health. Roseburia species thrive on fermentable fibers found in foods like oats, beans, lentils, onions, garlic, and asparagus. Resistance training remains the most reliable way to maintain muscle mass and power, especially with age. A varied diet rich in plants, fermented foods, and whole ingredients helps cultivate a more diverse gut microbiome.
