The dietary supplements glucosamine and chondroitin sulfate might slow joint damage for people with mild arthritis in their knees, according to a new study.
Previous research on the effectiveness of the supplements has been mixed, so experts remain divided on what the findings of this latest study mean for people with knee osteoarthritis, in which wear and tear over time damages the cartilage that lines the joints.
Among more than 30 parts of the knee joint measured in the new study, a handful differed between people who took the supplements and those who didn't over the course of two years.
The results could also be seen as an indication the supplements do not make a significant difference in arthritis symptoms or severity, one researcher said.
"This is yet another set of data arguing against any disease-modifying benefit of glucosamine and chondroitin sulfate," said Daniel Solomon, a rheumatologist and pharmacoepidemiologist at Brigham and Women's Hospital in Boston who was not involved in the study.
But another researcher thought the study might indicate a possible role for glucosamine and chondroitin, if only for people with milder arthritis.
"(The results) may reflect that drugs or therapies that affect joint structure in osteoarthritis are likely to have an effect earlier in the course of the disease," said Krishna Chaganti, a rheumatologist at the University of California, San Francisco, who also was not involved in the study.
The report's authors, led by Johanne Martel-Pelletier of the Osteoarthritis Research Unit at the University of Montreal Hospital Research Centre, were unavailable for comment.
They looked at data on 600 participants in an ongoing osteoarthritis study sponsored by the U.S. National Institutes of Health Osteoarthritis Initiative. Some of the study participants were taking bone-building drugs, some were taking pain relievers such as ibuprofen and some were taking glucosamine and chondroitin supplements.
Researchers used magnetic resonance imaging (MRI) to examine the spaces between the joints and monitored the participants' arthritis symptoms and disease progression over 24 months.
The people who took both anti-inflammatory pain medications and glucosamine and chondroitin supplements had less pain and milder changes due to disease in one part of the knee joint than those who took the pain drugs but no supplements.
Yet among those who were not taking pain medication, there was no difference in pain between people taking the supplements and those who didn't.
And overall, the people who took supplements had similar disease progression to those who did not take them.
In addition, given the sheer number of comparisons made at numerous points in the knees of each participant, the few statistically significant differences in knee anatomy that were seen may have been due to random variation, Solomon told Reuters Health in an email.
The study was funded in part by Bioiberica, a Spanish pharmaceutical company that manufactures glucosamine and chondroitin supplements.
In general, Solomon says, the results do not change the bottom line for osteoarthritis patients: glucosamine and chondroitin don't help.
"Few doctors recommend these agents," Solomon said, "and I doubt that (the study's results) will impact treatment in the U.S."
Chaganti thinks people with osteoarthritis can discuss the pros and cons of the supplements with their doctors. But she cautions that aside from questionable effectiveness, the downsides of glucosamine and chondroitin include a hefty price tag and possible safety risks, because supplements such as these are not regulated by the U.S. Food and Drug Administration.
"There are still some uncertainties regarding specifics about these supplements and their use," Chaganti said.