Evening primrose oil in rheumatoid arthritis: changes in serum lipids and fatty acids.

The serum concentration of lipids and composition of fatty acids after overnight fasting were studied in 18 patients with rheumatoid arthritis treated for 12 weeks with either 20 ml of evening primrose oil containing 9% of gamma-linolenic acid or olive oil. The serum concentrations of oleic acid, eicosapentaenoic acid, and apolipoprotein B decreased and those of linoleic acid, gamma-linolenic acid, dihomo-gamma-linolenic acid, and arachidonic acid increased during treatment with evening primrose oil. During olive oil treatment the serum concentration of eicosapentaenoic acid decreased and those of high density lipoprotein-cholesterol and apolipoprotein A-I increased slightly. The decrease in serum eicosapentaenoic acid and the increase in arachidonic acid concentrations induced by evening primrose oil may not be favourable effects in patients with rheumatoid arthritis in the light of the roles of these fatty acids as precursors of eicosanoids.