SEEN by ageing baby boomers as a miracle elixir for creaking or swollen joints, arthritic pain and general "wear and tear", bottles of glucosamine supplements have been marching off the shelves of the nation's health food stores, supermarkets and pharmacies.
Glucosamine is one of Australia's highest-selling health supplements ? worth more than $90 million a year ? yet remarkably, given its popularity, clinical trials have found that most formulations are ineffective.
People take glucosamine for osteoarthritis, a chronic condition that destroys bone joints and afflicts an estimated 1.3 million people in Australia. The number of people suffering the degenerative condition is expected to more than double in the next 30 years.
Despite clinical trial findings that many of the supplements do not work, manufacturers continue to claim that their product ? usually made from prawn and other crustacean shells ? consistently "alleviates symptoms," has been "scientifically proven to regenerate cartilage and synovial fluid" and "has been shown to slow the progression of joint damage in osteoarthritis".
Drug industry critic Ken Harvey has warned the federal Health Department's complaints resolution panel that glucosamine advertisements by Symbion, Blackmores and Doctors' Selection are inaccurate and misleading and could waste consumers' money.
Dr Harvey, of La Trobe University's school of public health, said some of the advertising claims were extravagant and were not backed by scientific evidence.
"There currently is no good evidence that any Australian preparation works, although there is some evidence overseas that one might," he said. "It really is an indictment of the Australian regulatory system that a product that is so popular and has such a high market share of complementary medicines has not been properly evaluated."
Vicki Kotsirilos, of the Australasian Integrative Medicine Association, said clinical studies indicated that glucosamine hydrochloride did not work. Other trials showed that a particular glucosamine sulphate might have some effect, but further research was needed, she said.
Dr Kotsirilos added that Australia's system of dealing with complaints about the advertising of complementary medicines needed beefing up.
Federal parliamentary health secretary Jan McLucas last week agreed, saying the current system lacked enforcement powers.
"It's very clear to me that we have to look at the whole process, including the advertising process," she said.
Consumers seem more than willing to swallow the claims made by manufacturers when it comes to glucosamine.
While thousands of people who suffer joint pain religiously take their tablets and capsules daily, the few independent clinical trials that have taken place question the benefits.
A study by Boston University last year concluded that glucosamine hydrochloride "is not effective" and that independent studies showed the other popular form, glucosamine sulphate, "has no effect", though there were too few trials to confirm this. Another study found that glucosamine sulphate "may be effective" in improving the symptoms of osteoarthritis of the knee but that more research was needed.
Wendy Morrow, executive director of the Complementary Healthcare Council, said Dr Harvey's evidence was biased and misleading and that the supplement worked for large numbers of people. Guidelines issued by the Therapeutic Goods Administration meant manufacturers had to have evidence to support the claims they made, she said.
Sydney's George Institute for International Health is examining the effect of glucosamine sulphate in a trial of 600 patients with knee osteoarthritis. The trial, which is still recruiting patients, will compare the benefits of glucosamine sulphate, a supplement extracted from cow and shark cartilage called chondroitin, and a combination of the two with a placebo, or fake, drug. The results are expected to be known in three years.
Dr Marlene Fransen, who is leading the study, said osteoarthritis was responsible for more disability in the daily lives of people aged over 50 than any other disease.
The biggest trial of glucosamine hydrochloride, involving 1600 people with arthritic knees, was conducted in 2006 in the United States by the National Centre for Complementary and Alternative Medicine and the National Institute of Arthritis and Musculoskeletal and Skin Diseases.
The trial compared the results of glucosamine hydrochloride, chondroitin sulphate, and a combination of the two, with a placebo.
Dr Harvey said the trial found no significant difference between the groups who took the supplements and the placebo. However, a small subgroup with moderate to severe knee pain did report significant relief when taking the combined glucosamine hydrochloride and chondroitin sulphate.
Dr Harvey also said that Australia's Adverse Drug Reactions Advisory Committee had warned that glucosamine could interact adversely with the blood-thinning medication warfarin. However, many glucosamine products lacked this warning and one manufacturer denied the risk on its website.