Simple Fiber Supplement Cuts Knee Arthritis Pain in Just 6 Weeks, Study Finds

A daily inulin supplement may help reduce knee osteoarthritis pain while revealing a possible link between gut health, muscle function, and pain sensitivity.

For millions of people living with knee osteoarthritis, managing chronic pain often means choosing between medications with unwanted side effects and exercise programs that can be difficult to maintain. Now, researchers have found evidence that relief may also come from an unexpected place: the gut microbiome.

A new clinical trial led by the University of Nottingham found that a daily prebiotic fiber supplement not only reduced knee pain in people with osteoarthritis, but also improved grip strength and lowered pain sensitivity. Participants taking the supplement were also far more likely to stick with the treatment than those assigned to a digital physiotherapy program.

The INSPIRE trial tested inulin, a naturally occurring dietary fiber found in foods such as chicory root and Jerusalem artichokes. Published in the journal Nutrients, the findings suggest that improving gut health could offer a simple, low-risk new approach for treating one of the world's most common causes of pain and disability among older adults.

"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, lead author of the study from the School of Medicine at the University of Nottingham.

Pain relief may start in the gut

The gut microbiome, the trillions of bacteria that live in the digestive system, helps shape many aspects of health, including how people experience pain. Inulin is a prebiotic, meaning it feeds beneficial gut bacteria. This process supports the production of short-chain fatty acids (SCFAs), especially butyrate, a compound that can affect inflammation and pain pathways across the body.

In the INSPIRE trial, people who took inulin had higher levels of butyrate and glucagon-like peptide-1 (GLP-1), a gut-released hormone linked to pain control and muscle health. Higher GLP-1 levels were also connected with better grip strength, suggesting a possible link between the gut and muscles that could lead to new areas of research.

Fiber proved easier to sustain

The six-week randomized controlled trial included 117 adults with knee OA and compared four groups: inulin alone, digital physiotherapy-supported exercise (PSE) alone, both treatments together, and a placebo. Inulin and physiotherapy each reduced knee pain on their own. However, only inulin improved grip strength and lowered pain sensitivity, which are measures related to how the nervous system processes pain.

The difference in dropout rates was notable. Only 3.6% of participants in the inulin group dropped out, compared with 21% in the physiotherapy group, suggesting that a daily supplement may be easier for many people to maintain than an exercise program.

Dr Kouraki said: "Our findings suggest that targeting gut health with a prebiotic supplement is a safe, well-tolerated, and effective way to reduce pain in people with knee osteoarthritis. The very low dropout rate compared to the exercise group is also encouraging from a public health perspective—people were able to fit this supplement easily into their daily lives."

A gut-muscle-pain link emerges

Senior author Professor Ana Valdes from the School of Medicine added: "The link we observed between GLP-1 and grip strength is particularly intriguing and points to a broader gut-muscle-pain axis that warrants further investigation. This could have implications not just for osteoarthritis, but for understanding how gut health influences aging and physical resilience more broadly."

Professor Lucy Donaldson, Director of Research at Arthritis UK, said: "The pain of arthritis can severely impact quality of life. Our recent lived experience survey showed that six in ten people are living in pain most or all of the time due to their arthritis.

"Researchers are starting to explore the role of the gut microbiome in our experience of pain. This exciting preliminary research highlights how diet and physiotherapy can act in different ways to have benefits for people with arthritis. We know a variety and balance of healthy foods, including fiber, and regular physical activity matter, and we're glad to be supporting research that explores how they work to help people with arthritis."

Reference: "Effect of Prebiotic Supplementation With and Without Physiotherapy on Pain and Pain Sensitivity in People with Knee Osteoarthritis" by Afroditi Kouraki, Susan Franks, Amrita Vijay, Thomas Kurien, Moira A. Taylor, Stephanie L. Smith, Benjamin Smith, Anthony Kelly and Ana M. Valdes, 23 February 2026, Nutrients.
DOI: 10.3390/nu18050714