The most widely investigated and used dietary supplements – glucosamine and chondroitin – do not deliver a clinically important effect in patients with osteoarthritis, a review of the evidence concludes.
Instead, the systematic review and meta-analysis of the evidence found lesser-known supplements such as Boswellia serrata extract, pycnogenol (pine bark extract) and curcumin might be more helpful.
The review identified 69 randomised controlled trials investigating 20 supplements for efficacy or safety in hand, hip or knee osteoarthritis. Most (84%) of trials were in the setting of knee osteoarthritis.
The meta-analysis found collagen hydrolysate, passion fruit peel extract, Curcuma longa extract, Boswellia serrata extract, curcumin, pycnogenol and L-carnitine demonstrated large and clinically important effects for pain reduction in the short term.
However none of the supplements delivered clinically important effects on pain in the medium or long term.
Undenatured type II collagen, avocado soybean unsaponifiables, methylsulfonylmethane, diacerein, glucosamine and chondroitin resulted in statistically significant improvements in pain, but did not meet pre-specified thresholds for clinical importance.
Chondroitin also demonstrated a statistically significant but not clinically important benefit in terms of structural improvement.
Only green-lipped mussel extract and undenatured type II collagen had clinically important effects on pain in the medium term, and none showed long term benefits.
Similar results were found for the effects of the supplements on physical function.
Lead author Professor David Hunter, from the department of rheumatology at the Royal North Shore Hospital, told the limbic glucosamine and chondroitin sales had benefited from marketing hype and positive publication bias.
Almost half of the studies were assessing glucosamine and chondroitin.
“Clinicians should be aware that a large proportion of patients are taking the supplements and many patients are strong advocates for their effects,” he said.
While the supplements appeared to be largely safe, he said it was wise for health professionals to maintain a healthy skepticism.
“Based on the quality of the trials, for those supplements that appear to have moderate to large effects, it would not be prudent to strongly advocate for their use until we have better quality evidence to support that.”
“I do however think it is important to be open-minded that some of the supplements will be supported by better quality trials in the future.”