Almost 400 patients with osteoarthritis of the knee participated in the 24-month, double-blind, placebo-controlled study, that is part of the second arm of the Glucosamine/Chondroitin Arthritis Intervention Trial (GAIT II).
However, the study’s findings may be undermined by admissions from the researchers, led by Allen Sawitzke from the University of Utah, School of Medicine in Salt Lake City. The limitations included a smaller than expected number of participants, large variations in measurements, and slower decline in the knee joint.
The study’s findings were published online yesterday in the journal Arthritis & Rheumatism.
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.
According to the Nutrition Business Journal, US sales for these combined supplements were $810 million (€563 million) in 2005.
Previous studies, including the $14m Glucosamine/chondroitin Arthritis Intervention Trial (GAIT), sponsored by the National Institute of Health, have reported positive results, while other have reported null results, leaving the subject clouded in uncertainty.
The new study does not help to clear the clouds, with the suggestion from Sawitzke and co-workers that the combination of the ingredients may be less effective than the glucosamine or chondroitin sulphate individually.
“The validity and mechanisms of this novel observation are uncertain but could be related to altered absorption of glucosamine,” wrote the researchers.
Study details
Three hundred and fifty-seven people with an average age of 56.9, previously assigned to one of the five groups in the first arm of the GAIT, continued these interventions. Daily interventions were 1,500 mg of glucosamine, 1,200 mg of chondroitin sulphate, a combination of both, 200 mg of celecoxib, or placebo for 24 months.
All the participants suffered from osteoarthritis of the knee, defined as grade 2 or 3 on the Kellgren/ Lawrence [K/L] scale, a well-established scale for osteoarthritis, and a loss of joint space width (JSW) of at least 2 mm at the start of the study. JSW relates to the narrowing of the space in the joint.
After two years of study, the average loss of JSW was 0.166 mm, said the researchers. There were no statistically significant differences between the groups compared to placebo, they added.
However, there was a suggestion that knees with a K/L grade 2 may respond to the intervention, and the researchers noted that this may be where the “greatest potential” could lie.
"While we found a trend toward improvement among those with moderate osteoarthritis of the knee in those taking glucosamine, we were not able to draw any definitive conclusions," said Sawitzke.
The results by no means close the door on this area of study, indicated the researchers. “In future osteoarthritis trials evaluating structural modification, K/L grade 2 knees may represent a more potentially responsive population; however, a larger sample size, longer study duration, and/or improved methods of measurement will be required, since the rate of JSW loss identified on plain radiographs is much slower than was previously recognized,” they concluded.
NutraIngredients-USA.com will run reaction to the study’s findings.
Source: Arthritis & RheumatismPublished online ahead of print, 29 September 2008, doi: 10.1002/art.23973“The effect of glucosamine and/or chondroitin sulfate on the progression of knee osteoarthritis: A report from the glucosamine/chondroitin arthritis intervention trial”Authors: A.D. Sawitzke, H. Shi, M.F. Finco, D.D. Dunlop, C.O. Bingham III, C.L. Harris, N.G. Singer, J.D. Bradley, D. Silver, C.G. Jackson, N.E. Lane, C.V. Oddis, F. Wolfe, J. Lisse, D.E. Furst, D.J. Reda, R.W. Moskowitz, H.J. Williams, D.O. Clegg