A simple dietary fiber supplement may offer a new way to ease knee osteoarthritis pain while also improving muscle strength, according to a clinical trial led by researchers at the University of Nottingham that links gut bacteria to how the body processes pain.
In the six-week INSPIRE trial, 117 adults with knee osteoarthritis were randomly assigned to take a prebiotic fiber called inulin, to undergo a digital physical therapy program, or both. Those taking inulin saw significant reductions in pain, improved grip strength and decreased sensitivity to pain, according to findings published in the journal Nutrients. Just 3.6% of participants assigned to inulin alone dropped out of the study, compared with 21% of those assigned to physical therapy alone — a gap the researchers said points to a treatment people find far easier to sustain than exercise programs.
How a fiber supplement might ease joint pain
Inulin is a naturally occurring fiber found in chicory root, Jerusalem artichokes and other vegetables. Unlike most nutrients, it passes undigested into the large intestine, where it feeds beneficial gut bacteria rather than supplying nutrients directly, classifying it as a prebiotic rather than a probiotic. When those bacteria ferment inulin, they produce short-chain fatty acids including butyrate, a compound that supports the intestinal lining and can influence inflammation and pain-related biological pathways.
"This study raises the exciting possibility that a simple dietary change — adding a fiber supplement to your breakfast or yogurt — could meaningfully reduce pain and improve physical function," said Dr. Afroditi Kouraki, the study's lead author at Nottingham's School of Medicine. Participants taking inulin showed higher levels of butyrate and of glucagon-like peptide-1, or GLP-1, a gut hormone that regulates blood sugar and appetite and has separately been linked to pain regulation and muscle health. GLP-1 is the same hormone targeted by diabetes and weight-loss drugs such as Ozempic and Wegovy, though the inulin used in the trial was not itself a GLP-1 medication.
Researchers found that participants with higher GLP-1 levels also tended to have better grip strength, though the study does not establish that the hormone caused the improvement. Knee osteoarthritis affects hundreds of millions of people worldwide and is a leading cause of chronic pain and disability, particularly among older adults, and current treatment typically relies on pain medication or exercise programs that many patients struggle to maintain.
