A simple daily fiber supplement can offer a surprising new way to relieve arthritic knee pain while improving muscle strength. In a clinical trial led by researchers at the University of Nottingham, people with knee osteoarthritis (OA) who took a prebiotic fiber called inulin experienced a significant reduction in pain, improved grip strength, and decreased sensitivity to pain.
The supplement also appeared to be much easier for participants to follow than a digital physical therapy program. Only 3.6% of those assigned to inulin alone dropped out of the study, compared to 21% of those assigned to physical therapy alone.
Published in the journal Nutrientsthe results suggest that improving gut health could become an additional strategy for managing arthritis. They also reveal a fascinating link between the bacteria living in our digestive system, the way our body processes pain and muscle function.
A Simple Dietary Change Could Help Relieve Arthritic Pain
Knee osteoarthritis affects hundreds of millions of people worldwide and is a major cause of chronic pain and disability, particularly among older adults. The disease develops as the tissues of the knee joint, including the cartilage that cushions the ends of the bones, gradually deteriorate. This can lead to pain, stiffness, swelling, and difficulty with daily activities such as walking or climbing stairs.
Treatment usually focuses on reducing symptoms and maintaining mobility. Painkillers can provide relief but may cause unwanted side effects, while physiotherapy and regular exercise can help improve joint function. However, following an exercise program can be difficult, especially for people already dealing with persistent pain.
The new research raises the possibility that a simple dietary supplement could be another way to manage symptoms.
“This study raises the exciting possibility that a simple dietary change – adding a fiber supplement to your breakfast or yogurt – could significantly reduce pain and improve physical function,” said study lead author Dr Afroditi Kouraki from the University of Nottingham School of Medicine.
The supplement tested in the study was inulin, a natural fiber found in foods such as chicory root, Jerusalem artichokes and some other vegetables. Unlike many nutrients, inulin is not broken down by digestive enzymes in the small intestine. Instead, it passes into the large intestine, where beneficial bacteria can use it as food.
How Gut Bacteria May Influence Arthritis Pain
Researchers are increasingly discovering that the gut microbiome, the vast community of microorganisms living in the digestive tract, influences much more than digestion. These microbes interact with the immune system, produce biologically active compounds, and can even affect how the nervous system responds to pain.
Inulin is classified as a prebiotic because it feeds certain beneficial gut bacteria rather than directly supplying live microorganisms, as probiotics do.
When bacteria ferment inulin, they produce substances called short-chain fatty acids (SCFAs). One of the most important is butyrate, a compound that helps support the intestinal lining and may influence inflammation and biological pathways involved in pain.
Researchers found that participants taking inulin had increased levels of butyrate, suggesting that the supplement influenced gut microbiome activity.
They also observed higher levels of glucagon-like peptide-1 (GLP-1), a hormone released by the gut that helps regulate blood sugar and appetite and has also been linked to pain regulation and muscle health.
GLP-1 has attracted a lot of attention because it is the hormone targeted by drugs such as Ozempic and Wegovy. However, the inulin supplement used in this trial was not a GLP-1 drug. Instead, the researchers examined whether supporting beneficial gut bacteria could influence the body’s own production of the hormone.
A particularly interesting finding was that higher levels of GLP-1 were associated with better grip strength. Although this does not establish that GLP-1 caused the improvement, it does suggest that changes originating from the digestive system could be linked to muscle function as well as pain.
Fiber Supplement vs Physiotherapy
To study these effects, researchers conducted the INSPIRE trial, a six-week randomized controlled study involving 117 adults with knee osteoarthritis.
Participants were assigned to one of four treatment groups: a daily inulin supplement alone, digitally supported physical therapy exercises (PSE) alone, a combination of inulin and physical therapy, or a placebo.
This design allowed researchers to examine the effects of the supplement and exercise separately, as well as determine whether their combination provided additional benefits.
Both inulin and physical therapy independently reduced knee pain, indicating that each approach provided significant symptom relief.
However, the supplement produced additional improvements that were not seen with physical therapy alone. Participants taking inulin demonstrated improved grip strength and reduced sensitivity to pain.
Pain sensitivity reflects the strength with which the nervous system responds to potentially painful stimulation. Reducing this sensitivity could be particularly helpful for people with osteoarthritis, because persistent pain is not always explained by the amount of visible damage within a joint. Changes in the way the nervous system processes pain can also contribute to discomfort.
Improved grip strength was another unexpected result, suggesting that the supplement’s effects might extend beyond the knee itself.
The researchers also found a substantial difference in the number of participants who completed their assigned treatments. Only 3.6% of the inulin-only group dropped out of the study, compared to 21% of the physiotherapy-only group.
This difference suggests that taking a daily fiber supplement may be easier to incorporate into a regular routine than following a structured exercise program.
A surprising link between gut health, muscles and pain
Dr Kouraki said: “Our results 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 easily integrate this supplement into their daily lives.
Beyond reducing arthritic pain, researchers are particularly interested in what the results reveal about the interactions between the digestive system, muscles and nervous system.
The association between GLP-1 and grip strength raises the possibility of a broader biological relationship linking gut health to physical performance and resilience as people age.
Lead 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 merits further investigation. This could have implications not only for osteoarthritis, but also for understanding how gut health influences aging and physical resilience more broadly. »
The results were promising, but the trial was relatively small and lasted only six weeks. Larger studies with longer follow-up periods will be needed to determine whether benefits persist, identify patients most likely to respond, and clarify the biological mechanisms responsible.
The results also don’t suggest that fiber supplements should replace exercise or other established arthritis treatments. Instead, they point to a potentially useful additional approach that could complement existing care.
A new direction for arthritis treatment
The potential importance of this research becomes clearer when we consider the number of people living with persistent arthritis pain.
Professor Lucy Donaldson, director of research at Arthritis UK, said: “Arthritis-related pain can have serious consequences on quality of life. Our recent lived experience survey showed that six in ten people live in pain most or all of the time because of their arthritis.
“Researchers are beginning to explore the role of the gut microbiome in our experience of pain. This exciting preliminary research highlights how diet and physiotherapy can work in different ways to benefit people with arthritis.
For people with knee osteoarthritis, the findings offer an encouraging possibility: A relatively simple change in daily diet can help reduce pain while supporting other aspects of physical health.
Perhaps most intriguing is that research suggests that treating arthritis may involve looking beyond the joints themselves. By exploring how gut bacteria influence inflammation, pain perception and muscle function, scientists could discover new ways to manage a disease that affects millions of people every day.
Gn Health
