Adverse Effects of Fish Oil

To the Editor.— Fisher et al¹ in their article on n-3 fatty acids and cellular aspects of atherogenesis suggest that urgent trials of n-3 fatty acid supplementation are needed to assess their effects on atherosclerotic disease. While epidemiological studies^2,3 have documented a reduced incidence of ischemic heart disease in populations with a high intake of n-3 fatty acids, there is also an unexplained increased incidence of stroke.^2,3 Apart from a high incidence of unpleasant side effects in patients taking fish oil supplements, clinical⁴ and laboratory studies⁵ have shown evidence of raised blood pressure in groups taking omega-3 fatty acid supplementation. In addition, recent epidemiological evidence has shown an increased incidence and prevalence of hypertensive related diseases³ in the same type of population in whom there is a low incidence of ischemic heart disease. While the theoretical benefits of n-3 fatty acid supplementation are