Janis C. KellyNov 27, 2012 Authors & Disclosures
Regular use of glucosamine, chondroitin, or fish oil supplements reduces high-sensitivity C-reactive protein (hs-CRP) by 16% to 22%, a marker of inflammation, according to a new study. Inflammation is now recognized as a factor in cancer and cardiovascular disease as well as many rheumatoid diseases. A number of over-the-counter dietary supplements are being marketed for the purpose of reducing inflammation, but data supporting the claims are limited.
To address this situation, Elizabeth D. Kantor, from the Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington, and colleagues analyzed data on dietary supplements and hs-CRP in 9947 participants in the National Health and Nutrition Examination Survey. In their article, published online November 8 in the American Journal of Epidemiology, the researchers report that regular use of glucosamine, chondroitin, or fish oil significantly reduced serum hs-CRP.
In participants who regularly used a supplement, the researchers found hs-CRP reductions of 17% (95% confidence interval [CI], 7% - 26%) with glucosamine, 22% (95% CI, 8% - 33%) with chondroitin, and 16% (95% CI, 0.3% - 29%) with fish oil compared with participants who did not take the supplements. The analyses were adjusted for age, gender, race, smoking history, and body mass index.
Effects Limited to Women
Kantor, who is a PhD candidate at the research center, told Medscape Medical News, "I was not particularly surprised by any of our findings. Our observation of an association between fish oil use and CRP supports recent randomized control trials which have shown fish oil to reduce CRP. Our observation of an association between use of glucosamine and chondroitin supplements and CRP aligns with laboratory studies which suggest that these supplements have anti-inflammatory properties. Further understanding these associations (and whether associations vary by gender) is an important step in evaluating the chemopreventive potential of these supplements."
The anti-inflammatory effects of glucosamine and chondroitin in the overall study population were driven by effects in women, who had hs-CRP reductions of 27% (ratio, 0.73; 95% CI, 0.61 - 0.88) with regular glucosamine use and 33% (ratio, 0.67; 95% CI, 0.53 - 0.84) with regular chondroitin use. Effects in men were small and nonsignificant.
The supplements methylsulfonylmethane, garlic, ginkgo biloba, saw palmetto, and pycnogenol were not associated with reduced inflammation.
The magnitude of the effect seen with the supplements is "comparable to what we and others have observed for the association between statin use and CRP," the authors write. "Our results suggest a biologic mechanism to substantiate the epidemiologic observation of an association between glucosamine and chondroitin use and reduced risk of chronic diseases."
However, not everyone is convinced by the data. Although Eric L. Matteson, MD, chair of the Department of Rheumatology at the Mayo Clinic in Rochester, Minnesota, does sometimes discuss use of fish oil supplements with his patients with arthritis, he told Medscape Medical News that he has some reservations about the clinical implications of the Kantor study.
"Data Interesting but Not Compelling"
"I find the data interesting but not compelling," Dr. Matteson said. "The hs-CRP is influenced by many factors, and it is not clear that even the very many adjustments for potentially interacting or confounding variables are able to permit a conclusion that it is in fact the putative exposure [to glucosamine, chondroitin, or ginseng] which leads to the lower hs-CRP. A direct interventional study would be needed to do that. People who take supplements may be otherwise more heath conscious than those who don't, which also could be contributing to the results."
Dr. Matteson added, "It is further not clear that the very low levels of inflammation suggested by the hs-CRP are relevant in arthritis. We don't use this test clinically to evaluate arthritis because it is too sensitive and too influenced by a host of other factors. This is why we only use the regular CRP for assessing inflammation in diseases like RA. It should be expected that use of these supplements would slow the development of [osteoarthritis], but there is no solid proof of this, so the relevance of the CRP reductions with respect to [osteoarthritis] is questionable."
Kantor, however, contends that the findings are clinically important. "We became interested in this area of research after observing that use of glucosamine, chondroitin, and fish oil supplements were associated with reduced risk of chronic diseases with which inflammation had been implicated. Our current study provides a plausible biologic mechanism by which these supplements may reduce risk of these diseases. The fact that these supplements have already been associated with the clinically relevant outcome provides potential clinical significance to these findings. However, further research is needed to better understand these associations and the potential clinical significance of these findings."
The study was supported by the US National Cancer Institute. The study authors and Dr. Matteson have disclosed no relevant financial relationships.
Am J Epidemiol. Published online November 8, 2012. Abstract