The main criticism of complementary therapies has always been a lack of scientific evidence or the poor quality of published studies. But this isn't true of glucosamine. A recent overview of the subject identified 20 high-quality clinical trials.
To test how well glucosamine works, researchers typically compare the pain levels experienced by groups of arthritis sufferers who are given glucosamine, a placebo or a non-steroidal anti-inflammatory drug (NSAID).
Research of this nature is controversial, because humans are complex organisms and studies inevitably produce conflicting results. And more often than not there¡¦s some detail in the way a trial is conducted that lays it open to criticism. Considered alone, individual studies are often only pointers ¡X the way forward comes from systematic evaluation of the evidence as a whole.
When we tested glucosamine two years ago the evidence for its effectiveness was looking good. But since then new research findings have seriously muddied the waters.
The UK-based Cochrane Collaboration looked at all published research up to January 2005 and concluded that the evidence is inconclusive because the research findings were inconsistent.
The eight most rigorous clinical trials failed to show any benefits from glucosamine over a placebo, whereas a series of studies using a glucosamine sulphate product from the Italian pharmaceutical company Rottapharm consistently showed clear benefits.
A large government-sponsored study in the US (GAIT) that tested glucosamine hydrochloride again found that glucosamine gave no better pain relief than a placebo. It came to the same conclusion for chondroitin sulphate. The only clear benefit was from glucosamine and chondroitin in combination, and then only for a small subgroup of people with moderate to severe knee pain.
A smaller European trial concluded that glucosamine (given as glucosamine sulphate) relieved pain better than a placebo but this trial was sponsored by Rottapharm. A more recent European trial, independent of drug company support, found glucosamine sulphate was no better than a placebo for treating hip osteoarthritis.
Most recently, an extension of the GAIT study reported on loss of cartilage in osteoarthritis of the knee. The researchers tested 357 people (with 581arthritic knees) and measured joint narrowing (using x-rays) before and after two years of treatment with any one of the following:
- Glucosamine hydrochloride (1500mg/day).
- Chondroitin sulphate (1200mg/day).
- A combination of glucosamine hydrochloride (1500mg/day) and chondroitin sulphate (1200mg/day).
- The NSAID celecoxib (200mg/day).
The study suggested that glucosamine and chondroitin sulphate, together or alone, were no better than placebo in slowing loss of cartilage. (Though the researchers pointed out that interpretation is complicated because the placebo group fared better than expected based on previous research findings.)
Some experts now say glucosamine hydrochloride isn't effective at all, and question the apparent benefits from glucosamine sulphate as coming from bias caused by industry sponsorship. To complicate matters, clinical trials consistently show a big placebo effect, where people feel less pain despite only taking dummy pills.
But this hasn't stopped some claims in ads and on labels that the benefits from glucosamine are 'clinically proven'. In reality the jury is still out.
Is glucosamine safe?
The one thing that clinical trials have proved with reasonable certainty is that glucosamine and chondroitin are generally safe for most people. However, there are some exceptions:
- If you suffer from an allergy to seafood you should avoid the majority of brands, where the glucosamine has been made from crustacean shells. Two brands ¡X Pretorius Professional Vegetarian Glucosamine 1500 and Bioorganics Vegetarian Glucosamine ¡X are of vegetable origin.
- If you have diabetes, check with your GP before taking glucosamine. While it appears safe in the short term, there's evidence that in the long term glucosamine could make your diabetes worse.
- People taking blood-thinning medicines, such as warfarin, should talk to their doctor before taking chondroitin, as it can increase the risk of bleeding. Chondroitin also occasionally causes stomach upsets.