11.01.08
Glucosamine and chondroitin sulfate, together or alone, do not effectively slow cartilage loss in the knees of osteoarthritis patients compared to placebo, according to a National Institutes of Health (NIH)-supported study.
Researchers from the Glucosamine/Chondroitin Arthritis Intervention Trial (GAIT) team reported their findings in the October issue of Arthritis & Rheumatism.
The two-year study, led by the University of Utah and conducted at several sites, investigated whether glucosamine and chondroitin sulfate supplements, alone or combined, could diminish the structural damage caused by osteoarthritis (OA). However, researchers say that compared to a placebo, neither had a clinically significant effect on slowing the rate of joint space width (JSW) loss, which is the distance between the ends of joint bones, as shown by X-ray.
This study was an ancillary, or additional, trial conducted by the GAIT team with a subset of participants from the original GAIT study, which sought to determine whether these dietary supplements could treat the pain of knee OA. Results from that first study, reported in 2006, suggested that overall the combination of glucosamine and chondroitin sulfate did not provide significant relief from pain among all participants. However, it did note that a smaller subgroup of study participants with moderate-to-severe pain showed significant relief with the combined supplements.
In the GAIT II trial, the group taking glucosamine had the least change in JSW, followed by the groups taking chondroitin sulfate, the drug celecoxib, placebo and the combination of both dietary supplements.
Andrew Shao, PhD, vice president, scientific and regulatory affairs with the Council for Responsible Nutrition (CRN), Washington, D.C., challenged the study, citing “major limitations” that question the conclusions.
“The results of the GAIT II trial are perplexing and extremely inconsistent with an existing large body of evidence that shows a benefit from glucosamine and chondroitin supplementation,” said Dr. Shao. “The results are also inconsistent with the first arm of GAIT, as well as with a series of previously published clinical trials, which examined the same outcome—the narrowing of the space between joints—and demonstrated clear benefit.”
Researchers acknowledged several study limitations and said interpreting results was complicated because participants taking placebo had a smaller loss of cartilage, or JSW, than predicted.
“The researchers expected to see a typical JSW narrowing of approximately -0.4 mm,” said Dr. Shao, “yet the actual JSW change in the placebo group was only -0.166 mm, substantially less than what was expected. Because the placebo group did not worsen as expected, there is no basis for comparison.”
Dr. Shao also believes the small sample left the study “grossly underpowered…making it highly difficult to draw any meaningful conclusions from the results.”
The findings from both GAIT trials are in direct conflict, according to Dr. Shao. “Examining a subset of the same subjects who experienced the most benefit from moderate-to-severe arthritis pain, GAIT II suggests that the same subgroup who experienced the most pain relief—those using the glucosamine and chondroitin combination—also experienced the most reduction in JSW. These two conclusions are inconsistent, without explanation, to say the least.”
Researchers from the Glucosamine/Chondroitin Arthritis Intervention Trial (GAIT) team reported their findings in the October issue of Arthritis & Rheumatism.
The two-year study, led by the University of Utah and conducted at several sites, investigated whether glucosamine and chondroitin sulfate supplements, alone or combined, could diminish the structural damage caused by osteoarthritis (OA). However, researchers say that compared to a placebo, neither had a clinically significant effect on slowing the rate of joint space width (JSW) loss, which is the distance between the ends of joint bones, as shown by X-ray.
This study was an ancillary, or additional, trial conducted by the GAIT team with a subset of participants from the original GAIT study, which sought to determine whether these dietary supplements could treat the pain of knee OA. Results from that first study, reported in 2006, suggested that overall the combination of glucosamine and chondroitin sulfate did not provide significant relief from pain among all participants. However, it did note that a smaller subgroup of study participants with moderate-to-severe pain showed significant relief with the combined supplements.
In the GAIT II trial, the group taking glucosamine had the least change in JSW, followed by the groups taking chondroitin sulfate, the drug celecoxib, placebo and the combination of both dietary supplements.
Andrew Shao, PhD, vice president, scientific and regulatory affairs with the Council for Responsible Nutrition (CRN), Washington, D.C., challenged the study, citing “major limitations” that question the conclusions.
“The results of the GAIT II trial are perplexing and extremely inconsistent with an existing large body of evidence that shows a benefit from glucosamine and chondroitin supplementation,” said Dr. Shao. “The results are also inconsistent with the first arm of GAIT, as well as with a series of previously published clinical trials, which examined the same outcome—the narrowing of the space between joints—and demonstrated clear benefit.”
Researchers acknowledged several study limitations and said interpreting results was complicated because participants taking placebo had a smaller loss of cartilage, or JSW, than predicted.
“The researchers expected to see a typical JSW narrowing of approximately -0.4 mm,” said Dr. Shao, “yet the actual JSW change in the placebo group was only -0.166 mm, substantially less than what was expected. Because the placebo group did not worsen as expected, there is no basis for comparison.”
Dr. Shao also believes the small sample left the study “grossly underpowered…making it highly difficult to draw any meaningful conclusions from the results.”
The findings from both GAIT trials are in direct conflict, according to Dr. Shao. “Examining a subset of the same subjects who experienced the most benefit from moderate-to-severe arthritis pain, GAIT II suggests that the same subgroup who experienced the most pain relief—those using the glucosamine and chondroitin combination—also experienced the most reduction in JSW. These two conclusions are inconsistent, without explanation, to say the least.”