The researchers from the University of Utah's School of Medicine who led the study say though some of their findings were confusing and more research was needed, after two years, there was no important reduction in joint space width loss.
The multicenter study which was funded by the National Center for Complementary and Alternative Medicine at the National Institutes of Health, supports other research which has shown the supplements have few or no effects.
A trial in 2006 - the glucosamine/chondroitin arthritis intervention trial or GAIT- found the supplements did not reduce the pain of knee arthritis, except among a small group of patients with moderate to severe pain.
Rheumatologist Dr. Allen Sawitzke and his colleagues say they had trouble interpreting their results because patients who took placebos had a smaller loss of cartilage than they should have.
The researchers however continued to watch 572 volunteers for another 18 months and found the supplements - 500 mg of glucosamine three times a day; or 400 mg of chondroitin sulfate three times a day; or a combination of the two supplements; or 200 mg of celecoxib daily; or a placebo - did not appear to slow the loss of cartilage, taken either alone or together and what is more they found the arthritis worsened in 24% of participants taking both - which was similar to those taking placebo.
Dr. Stephen Katz, director of the NIH's National Institute of Arthritis and Musculoskeletal and Skin Diseases says research continues to reveal that osteoarthritis, the most common form of arthritis, appears to be the result of an array of factors including age, gender, genetics, obesity and joint injuries.
Dr. Katz says because osteoarthritis affects nearly 21 million Americans, ways to not only treat pain, but also address the structural effects of the condition are being searched for.
"The immune responses directed to our DNA vaccine seem to be very broad," Ho says. "It could be that the vaccine in its current form could protect against most of the H5N1 viruses out there." And even if it can't, he notes, if a different strain of H5N1 begins to circulate, it should only take a few days to obtain its genetic sequence and adapt the existing vaccine to fight it.
A version of the consensus vaccine is already being produced, Ho says, so that it can move into human clinical trials as quickly as possible. And a separate electroporation study is under way at The Rockefeller University Hospital, this one examining the effectiveness of electroporation combined with a DNA vaccine against HIV.
Proceedings of the National Academy of Sciences 105(36): 13538-13543 (September 9, 2008)
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