Comparison of the effects of two low fat diets with different alpha-linolenic : linoleic acid ratios on coagulation and fibrinolysis

Fish oils rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DI- IA) have been demonstrated to alter coagulation and fibrinolysis variables. This study compared the effects of a traditional cholesterol-lowering diet and a similar diet, which had 50% of the linoleic acid (LA) replaced with the 18 carbon n-3 fatty acid, alpha-linolenic acid (ALA), on selected hemos tatic variables. After a 2-week run-in diet with 39.5% total energy (en) fr om fat, 29 healthy male subjects consumed a 31.5% en fat diet with approxim ately 7% en from polyunsaturated fat and an ALA:LA ratio of either 1:1.2 (A LA-rich, n = 15) or 1:21 (LA-rich, n = 14) for 6 weeks. Blood was collected at the beginning, middle and end of test diets for analysis of Factor VIIc and VIIIc, fibrinogen, von Willebrand factor, activated protein C resistan ce (APC(TM) resistance), tissue plasminogen activator and plasminogen activ ator inhibitor type-1 activities and/or protein concentrations and platelet fatty acids. The ALA-rich diet tripled the percentage of platelet EPA, (P< 0.0005) but had little effect on coagulation and fibrinolysis. The APC(TM) ratio demonstrated increased anticoagulant activity on the ALA-rich diet (P <0.001) only. Studies in patients with vascular pathologies are indicated t o corroborate the current findings. Greater ratios of ALA:LA, achievable on ly with greater amounts of polyunsaturated fat, may be necessary to produce the effects demonstrated after feeding fish oils. (C) 1999 Elsevier Scienc e Ireland Ltd. All rights reserved.