The Washington-DC-based dietary supplements trade groups the Natural Products Association (NPA) and the Council for Responsible Nutrition (CRN) called the study’s findings irrelevant, as did a member of the study’s oversight committee.
“This study’s findings are useless and I am surprised it has been published at all,” said Jason Theodosakis, oversight committee member and assistant professor of medicine at the University of Arizona.
Theodosakis, the author of a book on glucosamine and chondroitin and sports medicine expert, said the study should have been binned because it was deeply flawed for three major reasons:
- the sample size was too small (less than 400)
- the study length was too short (two years)
- the x-ray methodology was not sensitive enough to deliver meaningful measurements
The study followed a large 2006 National Institutes of Health-funded study called GAIT (glucosamine/chondroitin Arthritis Intervention Trial) that was published in the New England Journal of Medicine in 2006.
To see NutraIngredients.com review of the study published in the journal Arthritis & Rheumatism click here.
“In regard to the measuring device, if weight was used as an analogy, it would not have been able to discern between a thin person and an obese person – that’s how insensitive it was,” Theodosakis told NutraIngredients.com.
The x-ray technique used to measure the gap between bones in the study – a surrogate measure for the severity of osteoarthritis – had a precision error of 0.16mm - about the same bone gap loss for the placebo group over the whole two-year trial period.
“Even if the device had actually been able to measure any benefits, you need three years to gain real insights into how these nutrients work,” Theodosakis said. “The high quality studies in this area all show the effectiveness of chondroitin and glucosamine to osteoarthriitis.”
Daniel Fabricant, PhD, vice president, scientific and regulatory affairs at NPA criticized the study design and conclusions.
“Even the researchers seem to question their own findings,” he said. “If you look to the total body of research there is plenty of evidence that glucosamine and chondroitin do work for the estimated 20m Americans with osteoarthritis.”
“It’s just a shame that these kind of studies have the potential to damage the industry.”
Fabricant’s counterpart at CRN, Andrew Shao, PhD, called the results "perplexing and inconsistent" with the first GAIT results and other studies.
“This trial was a follow-up to the original GAIT trial, using only a small subset of the original cohort of patients. In addition, anecdotal reports from consumers overwhelmingly indicate that glucosamine and chondroitin or their combination are effective,” Dr Shao said.
GAIT 1 had 800 patients, but many dropped out at the mid-interval.
Even the study authors questioned the study’s findings, implying the ingredients may be less effective used together than individually. “The validity and mechanisms of this novel observation are uncertain but could be related to altered absorption of glucosamine,” wrote the researchers.
The trial included three hundred and fifty-seven people with an average age of 56.9, given interventions of 1,500 mg of glucosamine, 1,200 mg of chondroitin sulphate, a combination of both, 200 mg of celecoxib, or placebo for 24 months.
Josephine P. Briggs, MD, director of the National Center for Complementary and Alternative Medicine (NCCAM), at the National Institutes of Health (NIH), one of the study's funders said:
"While these results are of interest, we cannot draw definitive conclusions about the utility of glucosamine or chondroitin in reducing joint space width loss, in part because the placebo group fared better than anticipated based on prior research results. The results of the study provide interesting insights for future research."
Theodakis called for data from the trial that remained unpublished to brought to light including pain response, rescue medicine effects and side effects.
He said his enquiries into why this information had not been published had gone unanswered.
Glucosamine is extracted from the shell of crabs, lobster and shrimps. Cargill also markets a non-animal, non-shellfish derived product. The ingredient is often used in combination with chondroitin sulphate, extracted from animal cartilage, such as sharks.
NCCAM’s response to the study can be viewed here.