International Omega-3 Learning and Education Consortium for Health and Medicine

Osteoarthritis (OA) is a devastating progressive chronic joint disease. Increased omega-3 (n-3) polyunsaturated fatty acids (PUFA) supplementation has been advocated as an adjunctive therapy for OA. Osteoarthritis progressively causes loss of articular cartilage and changes in the surrounding synovium and subchondral bone. ¹ During the development of OA there is a loss of the homeostatic balance between anabolic and catabolic pathways in the cartilage, driven by cytokine cascades and the production of inflammatory mediators. ² There is a growing body of data indicating that n-3 PUFA (eicosapentaenoic acid EPA and docosahexaenoic acid DHA) have anti-catabolic and anti-inflammatory properties in the joint. Articular cartilage content of arachidonic acid (AA) correlated to OA severity in the joint and dietary n-3 PUFA (fish oil, EPA and DHA) supplementation decreased rat articular cartilage AA by 70%. ^3,4 In vitro data that examined the effects of n-3 and n-6 PUFA on cartilage explants showed that n-3 PUFA decreased interleukin (IL)-1-induced glycosaminoglycan (GAG) degradation and aggrecanase activity in a concentration-dependent manner. Additionally, n-3 PUFA decreased basal and IL-1 induced mRNA expression of aggrecanase, cyclooxygenase (COX)-2, lipoxygenase (LOX)-5, IL-1α, IL-1β, and tumor necrosis factor (TNF)α. The n-3 PUFA decreased basal and induced mRNA and protein expression of matrix metalloproteinase (MMP)-3 and MMP-13 in bovine chondrocyte cell cultures. ^5,6 In vivo, it has also been shown that dogs fed low amounts of n-3 PUFA had higher amounts of AA in the synovium and that correlated to increased PGE₂ in the synovial fluid, increased OA radiographic changes and decreased limb function. Conversely, dogs fed high levels of n-3 and low levels of n-6 PUFA had opposite effects. ⁷ These data support an important link between levels of dietary n-3 PUFA and cartilage metabolism. Several canine food products which have a high ratio of n-3 to n-6 PUFA and tout a therapeutic benefit for dogs with OA, have recently entered the market. While most of the data supporting these diets is anecdotal, one abstract presented recently found significant increases in ground reaction forces in dogs with OA after 90 days of a feeding trial. ⁸ More data are currently under review for publication and should be available soon.

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