Plasma lipoproteins and fatty acid composition during a moderate eicosapentaenoic acid diet

The effect of a diet rich in marine fatty acids, especially eicosapentaenoic acid, on plasma lipids (total plasma cholesterol, HDL cholesterol, total triglycerides and apolipoproteins A and B) and fatty acid composition in plasma phosphatidylcholine (PC) was studied in 10 healthy men. They were maintained for 11 weeks on their normal diet which was partly replaced by 150-200 g of fatty fish per day. In the same individuals this diet had previously caused a delay in primary haemostasis and a decrease in platelet aggregability similar to that caused by acetylsalicylic acid, a known inhibitor of thromboxane A2 formation. Apart from its effect on haemostasis, the fish diet substantially reduced serum triglycerides (by 43%, p less than 0.01) but caused no changes in total plasma or HDL cholesterol or apolipoproteins A and B. After three weeks on the diet the proportion of plasma PC omega-3 polyunsaturated fatty acids increased (C20:5 and C22:6) and omega-6 fatty acids decreased (C18:2 and C20:3). The relative plasma PC content of arachidonic acid was unaffected throughout. These alterations in plasma PC fatty acid composition were principally in accordance with those seen in platelet membrane PC. There was a linear correlation between the content of omega-3 and of omega-6 fatty acids in plasma PC with that of platelet PC as well as in predominate individual fatty acids of the two series. Six weeks after the volunteers had resumed their usual diet, total triglycerides and the fatty acid composition of plasma PC had returned to the original state.