A daily fibre supplement could help reduce pain and improve strength in people suffering from crippling knee pain, a new study has suggested.
The prebiotic fibre, known as inulin, is naturally found in vegetables such as chicory root and artichokes, and is sold online in powdered and capsule form for as little as 6p per dose.
But now experts at the University of Nottingham say taking it in supplement form could help relieve knee pain for people with osteoarthritis—a condition that causes joints to become painful and stiff.
Osteoarthritis is the most common type of arthritis in the UK and occurs when the protective cartilage on the ends of bones breaks down until the joints are no longer able to fully repair themselves.
Current treatment options rely heavily on pain medications, which carry risks of side-effects or extensive physiotherapy, which many patients struggle to maintain.
Dr Afroditi Kouraki, the study's lead author said: 'This study raises the exciting possibility that a simple dietary change - adding a fibre supplement to your breakfast or yoghurt - could meaningfully reduce pain and improve physical function.'
The study, published in the journal Nutrients, tracked changes in participants' gut bacteria linked to pain after they were exposed to inulin, physiotherapy, a combination of both or a placebo supplement.
The researchers expected inulin to have an effect on pain perception as it acts as a prebiotic, meaning it feeds beneficial gut bacteria.
This leads to the production of short-chain fatty acids, including butyrate which is known for its anti-inflammatory effects.
The study included 117 adults on the INSPIRE trial with knee osteoarthritis who were randomly assigned one of the conditions and followed up six weeks later.
Crucially, the researchers also didn't know which group had been given the fibre supplement.
Results showed that both daily inulin and physiotherapy independently reduced knee pain.
But the fibre supplement also led to improvements in grip strength and reduced pain sensitivity, which measures how the nervous system responds to pain.
Participants taking the daily supplement also showed increased levels of GLP-1, a hormone released by the gut that has been linked to improved muscle function and pain regulation.
At the beginning of the study participants completed a sit-stand test which measured how many times they could stand-up from a chair to a full standing position within 30 seconds.
Their lower body strength and functional mobility were also assessed using a standard test which involves standing up, walking three meters, turning around and returning to the starting position.
The main symptoms of osteoarthritis are joint pain and stiffness, and problems moving the joint
The grip test - which measures the force with which someone can squeeze an object - has long been considered a good assessment of physical health, with a strong grip linked to a reduced risk of dying from arthritis.
Finally, participants were asked to complete a questionnaire, both before the study period and six weeks after, which assessed pain, other symptoms, daily activity levels, sport and recreation function and knee-related quality of life.
Blood samples were also taken at the beginning of the study and again six weeks later.
One of the most promising findings of the study was that daily fibre intake could help improve how the nervous system processes pain.
Many people with osteoarthritis will experience heightened pain sensitivity, meaning that just normal pressure or movement can trigger a strong pain response.
But the researchers found that participants taking inulin experienced less severe knee pain than those on the placebo intervention, indicating reduced local pain sensitivity.
They also showed improvements in temporal summation, which measures how pain intensity increases when a stimulus is repeatedly applied.
Results also showed that those who took inulin everyday had higher circulating GLP-1 levels, which were associated with improved grip strength - which researchers suggested could point to a possible gut-muscle connection.
Those taking the daily fibre supplement increased their grip strength by around 4.6kg, compared with the placebo group.
This, researchers say, suggests that prebiotic fibre may influence muscle function, potentially through changes in metabolism or gut-related signaling pathways.
Interestingly, exercise along did not improve grip strength. But inulin alone didn't improve sit-to-stand performance.
Senior author Professor Ana Valdes said: '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 welcomed the findings: 'This exciting preliminary research highlights how diet and physiotherapy can act in different ways to have benefits for people with arthritis.'
According to Arthritis UK's most recent survey, six in 10 people with arthritis live in constant pain.
By the age of 70, around half of people will develop arthritis, but some are affected much younger.
Osteoarthritis, which affects around 10 million people in the UK, is the most common type of the condition.