Gut Bacterium Tied to 29% Stronger Grip in Older Adults
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- Roseburia inulinivorans was identified in a study published in the journal Gut as the only bacterial genus positively associated with both muscle mass and strength across age groups.
- Older adults carrying detectable levels of R inulinivorans showed 29% greater handgrip strength than peers without it, with the gap appearing without any corresponding rise in peak oxygen uptake.
- Mice given R inulinivorans weekly for eight weeks — after antibiotics wiped out their existing gut microbiome — gained about 30% more forelimb grip strength at weeks 4, 6, and 8 versus controls.
- R inulinivorans-treated mice developed larger muscle fibers and a significantly greater proportion of fast-twitch (type II) fibers in the calf's soleus muscle than animals given other Roseburia strains or none.
- The bacterium's abundance declined with age, ranging 0%–6.6% in 18- to 25-year-olds versus 0%–1.3% in the 65+ group, a drop that tracks the rising prevalence of sarcopenia.
- Researchers from the Netherlands and Spain conclude R inulinivorans is a 'potential probiotic candidate for preserving muscle strength,' though they note human Roseburia species failed to permanently colonize the mice's guts.
Why it matters: For adults over 65, where sarcopenia drives frailty and lost mobility, a probiotic that preserved grip strength by 29% — the gap between carriers and non-carriers — would address a population with virtually no pharmacological options. The parallel 30% grip gain in mice reinforces the gut-muscle axis hypothesis the researchers invoke, though the failure of human strains to colonize rodent guts means any nutraceutical path still needs long-term human testing.
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