Small effects of linseed oil or fish oil supplementation on postprandial changes in hemostatic factors

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 (DHA) 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 hemostatic variables. After a 2-week run-in diet with 39.5% total energy (en) from fat, 29 healthy male subjects consumed a 31.5% en fat diet with approximately 7% en from polyunsaturated fat and an ALA:LA ratio of either 1:1.2 (ALA-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 resistance (APC resistance), tissue plasminogen activator and plasminogen activator 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 ratio demonstrated increased anticoagulant activity on the ALA-rich diet (P < 0.001) only. Studies in patients with vascular pathologies are indicated to corroborate the current findings. Greater ratios of ALA:LA, achievable only with greater amounts of polyunsaturated fat, may be necessary to produce the effects demonstrated after feeding fish oils.

Postprandial lipaemia and haemostatic factors

Factor VII activity (FVIIc), a reported risk factor for fatal coronary heart disease, increases transiently after a fat-rich meal. The response shows dose-response characteristics and peak FVIIc and triglyceride concentrations above fasting levels tend to be positively associated. The mechanism is incompletely understood, but appears to require factor IX and the presence in plasma of lipoprotein products of lipolytic activity. Factor XII is not apparently essential. The increase in FVIIc is due to raised activated factor VII (FVIIa) activity, but is not associated with increased thrombin production or changes in fibrinolytic activity. The response of FVIIa appears independent of the proportions of saturated, monounsaturated and polyunsaturated fatty acids in the dietary fat, although dietary stearic acid may be less effective than myristic acid. However, in one study in which deliberate efforts were made to force an increase in plasma free stearic acid, its plasma level was positively associated with postprandial FVIIc. Because FVIIa initiates the thrombotic response to rupture of an atheromatous plaque, a raised postprandial level may represent a transient rise in the likelihood of a clinically significant coronary thrombosis.