Effects of dietary fish oil on platelet function and plasma lipids in hyperlipoproteinemic and normal subjects.

We studied the effects of dietary supplementation with an encapsulated fish oil concentrate (Maxepa) on platelet function, fibrinolysis, and plasma lipids and lipoproteins in 9 normal subjects, 10 patients with type IV hyperlipoproteinemia, and 6 with type IIB hyperlipoproteinemia. After a baseline period, the subjects crossed over randomly between treatment periods with Maxepa (providing 3.24 g eicosapentaenoic acid and 2.16 g docosahexaenoic acid per day) and safflower oil (used as a control), given for 6 weeks each. Administration of Maxepa led to a slight prolongation of the bleeding time in all groups and to modest inhibition of platelet aggregation in the type IV hyperlipoproteinemics and normal subjects, with partial (41%) inhibition of thromboxane synthesis from baseline levels noted in the normal group. Plasma total fibrinolytic actively did not change significantly in any group. Maxepa treatment resulted in a marked decrease in triglyceride and VLDL-cholesterol and a slight increase in HDL-cholesterol was noted after Maxepa in the type IV hyperlipoproteinemics (4.11 +/- 0.13 mmol/l vs. 3.10 +/- 0.16 mmol/l, Maxepa vs. safflower oil). We conclude that dietary supplementation with fish oil results in a relatively minor degree of inhibition of platelet function in normal and hyperlipoproteinemic subjects, and a potentially adverse increase in LDL-cholesterol in type IV hyperlipoproteinemics.