This Gut Bacterium May Help Keep Muscles Strong as You Age

Researchers from the Netherlands and Spain have identified a species of gut bacteria, Roseburia inulinivorans, that is associated with greater muscle strength in people and improved muscle performance in mice, according to a study published in the journal Gut.

The team analyzed stool samples from 90 healthy young adults aged 18-25 and 33 older adults aged 65 and above to identify which gut bacteria were linked to physical fitness, measured through hand grip strength, leg press and bench press performance, and VO2 max, a measure of cardiorespiratory fitness. Of all the bacteria detected, only the genus Roseburia showed a positive association with both muscle mass and strength, though individual species within it behaved differently.

Among older participants, those with detectable levels of R. inulinivorans had 29% greater handgrip strength than those without it, without a corresponding rise in peak oxygen uptake. In younger adults, higher levels of the bacterium were linked to both stronger handgrip and higher VO2 max. Roseburia bacteria were generally less abundant in older participants than in younger ones.

To test whether the bacterium directly influences muscle strength, the researchers depleted the gut microbiome of 32 mice with antibiotics, then gave three groups different Roseburia species weekly for eight weeks while a fourth group received none. Mice given R. inulinivorans showed about a 30% increase in forelimb grip strength after four, six and eight weeks, along with larger muscle fibers and a greater proportion of fast-twitch fibers, which are important for short bursts of intense activity.

The researchers said Roseburia inulinivorans could potentially be developed into a probiotic aimed at age-related muscle wasting, but cautioned that further research is needed to establish whether changing its levels actually causes changes in muscle function or is simply a consequence of it.