DIETARY FATTY-ACIDS IN HUMAN THROMBOSIS AND HEMOSTASIS

The effects of fatty acids on hemostasis are controversial. It has bee n difficult to show convincing effects of saturated or monounsaturated fatty acids that are clearly related to hemostatic variables in human s. Unsaturated fatty acids alter platelet aggregation and processes re lated to coagulation and fibrinolysis. Indirect evidence exists that n -6 polyunsaturated fatty acids may exert favorable effects on thrombot ic processes in vivo, but large clinical trials have failed to show be nefits of 5-6 g linoleic acid (18:2n-6) or linolenic acid (18:3n-3)/d. Only long-chain n-3 fatty acids prolong the template bleeding time, a nd they may exert some beneficial effect on erythrocyte flexibility. I t appears unlikely that n-3 fatty acids lower fibrinogen or interact w ith the fibrinolytic system directly. One prospective secondary preven tion trial showed benefits that may have resulted from either an impro ved hemostatic profile or an antiarrhythmic effect. A similar time cou rse of clinical improvement was noted with reduced rates of cardiac mo rtality and postoperative thrombosis in Norway during World War II, an d this was associated with a drastic dietary alteration involving incr eased consumption of n-3 fatty acids and reduced consumption of satura ted fatty acids. Further work is needed to develop better tools to exa mine in vivo hemostasis so that the mechanisms and eventual clinical u tility of n-3 fatty acids can be elucidated in well-designed clinical trials.