Nutrients: Inulin reduced osteoarthritis pain and improved muscle strength within six weeks

A randomized controlled trial conducted by the University of Nottingham has found that a daily prebiotic fiber supplement can reduce pain in people with knee osteoarthritis. The results suggest that its pain-relieving effect is comparable to physiotherapy, while participants were far more likely to stick with the supplement than with exercise therapy. The findings were published in the journal Nutrients.

The INSPIRE trial included 117 adults with confirmed knee osteoarthritis who were randomly assigned to one of four groups: inulin (a prebiotic fiber derived from chicory root), physiotherapy, a combination of both treatments, or a placebo.

After six weeks, both inulin supplementation and physiotherapy produced similar reductions in knee pain. However, only the inulin group showed improvements in handgrip strength and a reduction in pain sensitivity, a measure of how the nervous system processes pain signals.

Researchers also observed increased levels of GLP-1 (glucagon-like peptide-1), a gut hormone involved in pain regulation and muscle health, among participants taking inulin. Higher GLP-1 levels were associated with greater improvements in grip strength.

At the same time, the inulin group experienced an increase in butyrate, a short-chain fatty acid produced when gut bacteria ferment inulin. Butyrate is known to help suppress inflammatory processes.

"The link between GLP-1 and muscle strength is particularly intriguing because it points to a broader gut-muscle-pain axis that deserves further investigation," said Professor Ana Valdes. "This could have implications not only for osteoarthritis but also for understanding how gut health influences healthy aging and physical resilience."

The study also found a striking difference in treatment adherence. Only 3.6% of participants in the inulin group dropped out, compared with 21% of those receiving physiotherapy. According to the researchers, adding a spoonful of prebiotic powder to breakfast or yogurt may be easier for many patients than maintaining a regular exercise routine.

Lead investigator Aphrodite Kouraki noted that prebiotic fiber is safe, well tolerated, and already available over the counter. Future studies will examine whether different types of prebiotics work through similar biological mechanisms and whether the benefits persist beyond the six-week study period.