Low quality of evidence for glucosamine-based nutraceuticals in equine joint disease: review of in vivo studies.

Nutraceuticals are increasingly applied to the management of equine arthritis and joint disease, particularly those based upon glucosamine and chondroitin sulphate. While the first report of using glucosamine in horses appeared more than 25 years ago, it was not until 1992 that isolated studies began to be reported. Since that time, 15 in vivo papers have been published in the equine literature, usually on products already commercially available and often seeking evidence for efficacy. These studies demonstrate an encouraging trend to manufacturers of these products investing in research, but most do not meet a quality standard that provides sufficient confidence in the results reported. This review discusses the entirety of published in vivo research on glucosamine-based nutraceuticals (GBN) for horses, including that on Cosequin, Cortaflex, Synequin, Sasha's EQ, Myristol, chondroitin sulphate, glucosamine sulphate and glucosamine hydrochloride; and considers experimental limitations of this research along with their impact on interpretation of results. A quality score was calculated for each paper according to preset quality criteria. A minimum quality standard of 60% was set as the threshold for confidence in interpretation of results. Of the 15 papers reviewed, only 3 met the minimum quality standard. Experimental limitations of each research paper are discussed. It is concluded that the quality of studies in this area is generally low, prohibiting meaningful interpretation of the reported results. New high quality research on GBN for horses is needed and recommendations for future research are discussed.