A new study has found that a prebiotic fibre supplement reduced pain, improved grip strength, and lowered pain sensitivity in people with knee osteoarthritis (OA) - with far fewer dropouts than a digital physiotherapy programme.
The INSPIRE clinical trial, led by experts at the University of Nottingham, showed that taking a daily supplement of inulin- a natural dietary fibre found in chicory root, Jerusalem artichokes and other vegetables – significantly reduced pain in people with OA.
The results, which are published in the journal Nutrients, suggest that improving gut health could be a promising new approach to managing one of the most common and debilitating chronic conditions in older adults.
Knee OA affects hundreds of millions of people worldwide and is a leading cause of pain and disability, particularly in older adults. Current treatment options rely heavily on pain medications, which carry risks of side effects, or exercise programmes, which many patients struggle to maintain.
“This study raises the exciting possibility that a simple dietary change - adding a fibre 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.
The gut microbiome - the trillions of bacteria living in our digestive system, plays a wide-ranging role in people’s health, including how we experience pain. Inulin acts as a prebiotic, meaning it feeds beneficial gut bacteria. This leads to the production of short-chain fatty acids (SCFAs), particularly a compound called butyrate, which can influence inflammation and pain pathways throughout the body.
In the INSPIRE trial, participants who took inulin showed increased levels of both butyrate and glucagon-like peptide-1 (GLP-1) — a hormone released by the gut that has been linked to pain regulation and muscle health. Higher GLP-1 levels were associated with improved grip strength, pointing to a possible gut-muscle connection that could open up exciting new avenues of research.
The six-week randomised controlled trial involved 117 adults with knee OA and tested four groups: inulin alone, digital physiotherapy-supported exercise (PSE) alone, a combination of both, and a placebo. Both inulin and physiotherapy independently reduced knee pain. However, inulin uniquely improved grip strength and reduced pain sensitivity, measures linked to how the nervous system processes pain, while physiotherapy did not.
Strikingly, the dropout rate for the inulin group was just 3.6%, compared to 21% for those in the physiotherapy group - suggesting that a daily dietary supplement may be easier for people to stick with than an exercise programme.
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."
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 ageing 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 fibre, and regular physical activity matter, and we’re glad to be supporting research that explores how they work to help people with arthritis.”
The full study can be found here.