Daily fiber supplement reduces knee arthritis pain and improves strength

Researchers at the University of Nottingham led the INSPIRE clinical trial, which tested inulin, a natural dietary fiber found in chicory root, Jerusalem artichokes, and other vegetables. The six-week randomized controlled trial included 117 adults with knee osteoarthritis (OA). Participants were divided into four groups: inulin alone, digital physiotherapy-supported exercise (PSE) alone, both treatments together, or a placebo.

Published in the journal Nutrients, the findings show that both inulin and physiotherapy independently reduced knee pain. However, only the inulin group experienced improved grip strength and lower pain sensitivity – measurements that reflect how the nervous system detects and processes painful signals. The inulin group also had a much lower dropout rate: only 3.6% left the study, compared with 21% in the physiotherapy group.

The researchers found that inulin nourishes beneficial gut bacteria, which produce short-chain fatty acids (SCFAs) such as butyrate, and increases levels of glucagon-like peptide-1 (GLP-1), a gut hormone involved in pain regulation and muscle health. Higher GLP-1 levels were linked to better grip strength, suggesting a gut-muscle-pain connection that warrants further investigation.

Senior author Professor Ana Valdes from the School of Medicine said the link between GLP-1 and grip strength points to a broader gut-muscle-pain axis. Professor Lucy Donaldson, Director of Research at Arthritis UK, noted that this preliminary research highlights how diet and physiotherapy can act in different ways to benefit people with arthritis.

Lead author Dr. Afroditi Kouraki emphasized that a simple dietary change – adding a fiber supplement to breakfast or yogurt – could meaningfully reduce pain and improve physical function. The low dropout rate indicates that such a supplement is easy to incorporate into daily life.