Nutraceuticals in the management of osteoarthritis : a critical review.

Osteoarthritis (OA) is a chronic, highly prevalent and disabling disease that is expected to increase in prevalence secondary to longer life expectancy and a disproportionately aging population. Treatment of OA is only marginally effective and has been focused primarily on symptom control using weight loss, physical therapy, nonsteroidal anti-inflammatory drugs (NSAIDs), acetaminophen, intra-articular steroids or viscosupplementation, topical NSAIDs and analgesics, diacerein (an oral interleukin-1β inhibitor) and finally joint replacement surgery. The use of nutraceuticals in the treatment of OA is common, and scientific studies examining the effects of nutraceuticals on the pathogenesis and treatment of OA are increasing. This review examines the efficacy and safety of select nutraceuticals for the treatment of OA. The reviewed nutraceuticals include glucosamine, chondroitin, collagen hydrolysates (CHs) and avocado-soybean unsaponifiables (ASUs). There have been several clinical trials examining the efficacy of these products and the results demonstrate significant heterogeneity. Significant improvements in pain, function and structural outcomes have been shown for some of the treatment arms or subgroups of patients, but the effects are not consistent across the studies. Glucosamine, chondroitin and the two in combination have been the most extensively studied. Significant improvement in pain and functional indices and a decrease in the loss of joint space width were demonstrated in some but not all studies. CHs showed significant improvement in pain and functional indices for several subgroups of patients, but these findings were not pervasive amongst the treatment arms. ASU has demonstrated positive results with respect to decreased NSAID use in several studies and functional and pain end points in most of the reviewed studies; however, in the two studies examining structural end points, the results were mixed. The safety of these nutraceuticals has been demonstrated across all of the reviewed trials, and there were no significant issues with tolerance. Given the good safety profile of nutraceuticals, the marginal efficacy of conventional treatments, the high prevalence and rate of disability from OA and the possible benefit of nutraceuticals to patients with OA, use of nutraceuticals in select patients is appropriate. An overall recommendation to use nutraceuticals in the treatment of all patients with OA is not strongly supported by the available data. Future studies should focus on standardization of symptomatic and structural outcome measures, be of longer duration and pay careful attention to the content of the investigational product.