Intake of Fish and Omega-3 Fatty Acids and Risk of Stroke in Women

Abstract

An inverse relationship between fish intake and risk of stroke has been reported in several,^1,2 but not all,^3,4 prospective studies. Mechanisms for protection against stroke by fish intake may include inhibition of platelet aggregation^5,6; lowered blood viscosity⁶; suppressed formation of leukotrienes (lipid mediators for neutrophil and macrophage aggregation)⁷; and reduction of plasma fibrinogen⁸ blood pressure levels⁹ and insulin resistance.¹⁰ The possibility that fish consumption may increase the risk of hemorrhagic stroke was suggested by ecologic studies in which Greenland Eskimos with very high intake of omega-3 polyunsaturated fatty acids (omega-3 fatty acids) had an excess risk of mortality from hemorrhagic stroke compared with Danish whites.^11,12 However, the average food supply per capita for omega-3 fatty acids (eicosapentaenoic acid and docosahexaenoic acid) among persons living in the United States is about 0.1 to 0.2 g/d,¹³ much lower than that of Danish whites (0.8 g/d) and Greenland Eskimos (10.5 g/d).¹⁴ Thus, the potential for any increased risk of hemorrhagic stroke may be minimal at the average intake level of US residents. To our knowledge, no prospective study has examined previously the relationship between intake of fish and omega-3 fatty acids and risk of stroke by stroke subtype. We investigated this relationship prospectively during 14 years of follow-up. Our a priori hypothesis was that intake of fish and omega-3 fatty acids would be associated with reduced risk of ischemic stroke and would not be associated with increased risk of hemorrhagic stroke among middle-aged US women.