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In a six-week randomized trial involving 117 adults with knee osteoarthritis, participants assigned to daily inulin reported reduced knee pain and showed improved grip strength and lower pain sensitivity. The results are promising but do not establish that inulin works for everyone or that gut changes caused the improvements.
A six-week randomized trial led by University of Nottingham researchers found that adults with knee osteoarthritis assigned to daily inulin fiber experienced reduced knee pain, improved grip strength and lower sensitivity to pain. The findings, published in Nutrients, point to a possible dietary addition to arthritis care, but do not show that fiber can replace exercise, medication or other treatment.
The INSPIRE trial enrolled 117 adults with knee osteoarthritis, a condition involving gradual deterioration of tissues in the knee joint that can cause pain, stiffness and difficulty with everyday movement. Participants were assigned to one of four groups: daily inulin alone, digitally supported physical therapy exercises alone, both approaches together, or a placebo. The trial lasted six weeks.
According to the study report, both inulin and physical therapy independently reduced knee pain. Inulin was also associated with improvements in grip strength and reduced pain sensitivity, outcomes that the report says were not seen with physical therapy alone. Grip strength is a measure of hand strength, not a direct measure of knee function, and the results do not establish why it changed.
Study participants assigned to inulin alone were less likely to leave the trial than those assigned to physical therapy alone: 3.6% dropped out of the inulin-only group, compared with 21% in the physical-therapy-only group. That difference describes retention in this study; it does not by itself prove that fiber is easier to use for all patients or that it is more effective than exercise.
A Possible Addition to Arthritis Care
Knee osteoarthritis affects mobility and can make sustained exercise difficult for people living with pain. The trial raises the possibility that a low-effort dietary supplement could complement established approaches, particularly if future studies confirm the pain and strength findings. The lower dropout in the inulin-only group also suggests that adherence may be worth examining when researchers compare options for people who struggle to maintain exercise programs.
The results do not establish inulin as a replacement for physical therapy. Both approaches reduced pain in the trial, and the study lasted only six weeks. Nor does improved grip strength show that participants’ knee strength or ability to walk improved. The findings are best understood as early clinical evidence that a gut-focused intervention may affect outcomes beyond digestion, not as a treatment recommendation.
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How Inulin Was Studied
Inulin is a prebiotic fiber found naturally in foods including chicory root and Jerusalem artichokes. It passes through the small intestine without being broken down by digestive enzymes and can be used by bacteria in the large intestine. This differs from probiotics, which supply live microorganisms.
The researchers reported that participants taking inulin had increased levels of butyrate, a short-chain fatty acid produced when gut bacteria ferment fiber, and higher levels of GLP-1, a hormone released by the gut. Higher GLP-1 levels were associated with better grip strength. These observations may help guide further research into links between gut activity, pain processing and muscle function, but associations do not show that either change caused the measured outcomes.
GLP-1 is also the hormone targeted by medicines such as Ozempic and Wegovy, but the supplement in this trial was not a GLP-1 drug. The study examined whether feeding gut bacteria with inulin might influence the body’s own hormone levels; it did not test those medicines as arthritis treatments.
“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.”
— Dr. Afroditi Kouraki, lead author and researcher at the University of Nottingham School of Medicine
What the Trial Cannot Establish
The report describes a 117-person trial lasting six weeks; it does not establish whether the effects persist over longer periods, apply to people with other forms of arthritis, or vary by age, diet or disease severity. The source material does not give the size of the pain reductions, the supplement dose, or enough detail to assess the clinical importance of each change.
The reported increases in butyrate and GLP-1, along with the association between GLP-1 and grip strength, do not prove a causal pathway. It remains unclear whether the inulin-related gut changes produced the improvements, whether other factors contributed, or whether combining inulin with physical therapy offers greater benefit than either approach alone. The report also does not provide detailed information on side effects or longer-term safety.
Further Trials Must Test Durability
The findings support further research, including longer and larger trials that measure pain, daily function, strength, adherence and side effects over time. Researchers will also need to clarify whether inulin adds meaningful benefit to physical therapy and whether changes in gut bacteria or hormone levels explain any clinical effects. Until more evidence is available, the trial does not establish a standard arthritis treatment. People considering a fiber supplement for a health condition should discuss that decision with a qualified health professional.
Key Questions
What did the study find?
In a six-week trial of 117 adults with knee osteoarthritis, the inulin group had reduced knee pain, improved grip strength and lower pain sensitivity, according to the study report. The findings need confirmation in further research.
Was inulin more effective than physical therapy?
The report says both inulin and digitally supported physical therapy reduced knee pain. Inulin was also linked to improvements in grip strength and pain sensitivity not observed with physical therapy alone. The study does not establish that supplements should replace exercise or physical therapy.
Does inulin work like Ozempic or Wegovy?
No. Inulin is a prebiotic fiber, not a GLP-1 medication. Researchers reported higher levels of the body’s GLP-1 hormone among participants taking inulin, but the trial did not test Ozempic or Wegovy as arthritis treatments.
Does the study prove gut bacteria caused the pain reduction?
No. The researchers reported changes in butyrate and GLP-1, but those findings do not establish that gut changes caused the pain or strength outcomes. The mechanism remains uncertain.
Source: sciencedaily.com
