Daily fiber supplement eased knee arthritis pain and improved grip strength

Researchers at the University of Nottingham in the UK have found that inulin, a prebiotic fiber, can reduce pain in people with knee osteoarthritis, a condition in which the tissues and cartilage of the knee gradually deteriorate. The findings, published in the journal Nutrients, suggest that improving gut health could become an additional approach to managing arthritis.

How the trial worked

The six-week randomized controlled study, called INSPIRE, involved 117 adults with knee osteoarthritis. They were split into four groups: a daily inulin supplement, digitally supported physical therapy exercises, both combined, or a placebo.

Inulin and physical therapy each reduced knee pain on their own. People taking inulin also showed better grip strength and lower sensitivity to pain, which was not seen with physical therapy alone.

More participants stayed the course with the supplement. Only 3.6% of those assigned to inulin alone dropped out, compared with 21% of the physical therapy-only group.

Possible mechanism

Inulin, found naturally in chicory root and Jerusalem artichokes, is not broken down by enzymes in the small intestine. In the large intestine, beneficial bacteria ferment it into short-chain fatty acids, including butyrate. Butyrate levels were higher among inulin users. Levels of the gut hormone GLP-1, which is targeted by drugs such as Ozempic and Wegovy, also rose, although the supplement in this trial was not such a medication. Higher GLP-1 was linked to better grip strength, but the researchers stress this does not prove cause and effect.

Caution

Lead author Dr. Afroditi Kouraki described the supplement as safe and well tolerated. The researchers acknowledge that the trial was small and short, so larger and longer studies are needed. Fiber supplements are not intended to replace exercise or other established treatments, but to complement them.

Professor Lucy Donaldson, Director of Research at Arthritis UK, said the charity's survey found that six in ten people with arthritis live in pain most or all of the time.