Dietary fish oil (4 g daily) and cardiovascular risk markers in healthy men

Some epidemiological observations indicate that 1 to 2 weekly servings of fish prevent ischemic heart disease (IHD). This might be explained by an effect of the very-long-chain n-3 polyunsaturated fatty acids (n-3 VLCPUFA) of fish oil on lipid metabolism and/or the hemostatic system, both involved in IHD development. We studied the effect of incorporating natural fish oil (4 g daily equivalent to 0.91 g n-3 VLCPUFA and corresponding to one to two weekly servings of fatty fish) into the diet in a 4-week parallel, randomized, and double-blind trial of 47 healthy males aged 29 to 60 years. Sunflower oil was used as placebo. The fish oil had no significant effect on plasma lipids, apolipoproteins, lipoprotein(a), blood coagulation FVII, fibrinogen, endogenous fibrinolysis, beta-thromboglobulin, von Willebrand factor, glucose, or insulin in fasting blood samples. In nonfasting samples (n = 19), fish oil was associated with an approximately 30% decline in plasma triglycerides (P < .02) and a 9% decline in FVII protein (P < .05), whereas FVII coagulant activity and fibrinolysis were unaffected. In conclusion, our findings indicate that lowering of postprandial triglycerides is the only n-3 VLCPUFA effect that could contribute to primary prevention of IHD in healthy middle-aged men as assessed by currently measurable lipid and hemostatic risk markers.