Interactions between dietary fat, fish, and fish oils and their effects on platelet function in men at risk of cardiovascular disease

Recent studies have suggested that omega 3-fats of marine origin may have a protective role in heart disease. This study aimed to compare the effects of fish or fish oil, in the setting of a high- or low-fat diet, on platelet aggregation and platelet thromboxane in men with increased risk of cardiovascular disease. One hundred twenty men who were nonsmokers, 30 to 60 years old, with mildly elevated blood pressure and cholesterol were randomly allocated to one of five high-fat (40% of daily energy) or two low-fat (30%) groups for 12 weeks. The five high-fat groups took either 6 or 12 fish oil capsules daily; fish; a combination of fish and fish oil; or placebo capsules. The two low-fat groups took either fish or placebo capsules. Fish meals provided 1.3 g of eicosapentaenoic acid daily, equivalent to 6 fish oil capsules, and contained an average of 3.65 g/d of omega 3-fatty acids. Multiple regression analysis of the combined groups showed that all groups taking omega 3-fatty acids reduced platelet aggregation to both collagen (P<.0001) and platelet-activating factor (PAF) (P<.05) and platelet thromboxane B-2 responses (P<.05) to collagen-induced aggregation. The low-fat diet alone had no effect on PAF-induced platelet aggregation and only a small effect on platelet responses to collagen (P<.05). Platelet aggregation responses to PAF were reduced more by fish oil than fish in a high-fat diet, whereas fish had a greater effect when part of a low-fat rather than a high-fat diet. There was no significant difference in collagen-induced platelet aggregation or platelet thromboxane between fish and fish oils on a high or low fat intake. In conjunction with our previous findings of improvements in lipoproteins, blood pressure, and heart rate in this population, these results on platelet function suggest that dietary omega 3-fatty acids incorporated into a low- rather than a high-fat diet have a wider spectrum of more favorable effects on cardiovascular risk factors.