Widely vaunted supplements and diets that have been claimed to combat the crippling effects of common forms of arthritis have no significant proven benefits, according to new research.
The study, led by Dr Suzanne Verstappen of the University of Manchester, looked at 24 separate reviews and 150 research articles published between 2013 and 2018, on the use of diet and supplements for osteoarthritis and rheumatoid arthritis.
Fish oil, omega 3, chondroitin, glucosamine, vitamin D, avocado and soybean as well as a Mediterranean diet are widely marketed as helping to alleviate symptoms. But the research, published in the British Medical Journal, concludes that evidence shows “no single dietary intervention which has substantial benefits on the outcomes of people” with osteoarthritis and rheumatoid arthritis.
More than 400,000 people in Ireland have osteoarthritis, a gradual condition typically causing pain and restricted movement in larger joints, such as the spine, hips, knees and hands. Thousands more suffer rheumatoid arthritis, the second most common form of the disease, which causes pain and stiffness in inflamed joints, most commonly in those aged 40-70. There is no cure for either condition.
The latest meta-analyses of existing studies found they were often “at moderate to high risk of bias” and could be compromised by the “influence of commercial sponsors”.
Any direct impact shown by switching diet or taking supplements was “small and not clinically meaningful” and “unlikely to make any difference to the progression of osteoarthritis and rheumatoid arthritis”, it found.
Evidence for dietary interventions was “poor or very poor” for both conditions, and although there was “moderate quality evidence for probiotics, vitamin D, fish oil/omega 3″ in treating rheumatoid arthritis, “the impact was either negligible or too small to make much difference”.
Dr Clodagh Twoomey, a research fellow at University of Limerick investigating osteoarthritis, said misinformation about purported benefits of diet and supplements was “rampant”.
“There are more ads on TV for supplements than there are for exercise programmes and teaching you how to deal with pain, manage your pain and give you long term benefits — which are also less expensive.”
Popular supplements glucosamine and chondroititis can cost up to €35 for a month’s supply, omega 3 and fish oils as much as €50, and vitamin D €12. That is almost €100 a month combined.
Dr Twoomey said these had a “small effect if any at all”.
“It comes back to people wanting to take a pill to cure their problems as opposed to putting in the work to self-manage the disease ... If we could bottle exercise we would make a fortune.”
Prof Gerry Wilson, a consultant rheumatologist who leads the UCD Centre for Arthritis Research, said there was “scant evidence” for the benefits of anti-inflammatory diets.
“But they can be a good thing if you need to improve your general health — both diet and exercise,” he said. “There is definitely a link between obesity and osteoarthritis, and the only thing that has been shown to modify the condition is reducing your BMI (body mass index).”