1. Twelve healthy male subjects took a daily supplement of 20 ml of cod-liver oil for 6 weeks. This provided 1.8 g of eicosapentaenoic acid (20:5ω3) and 2.2 g of docosahexaenoic acid (22:6ω3). The effects of the supplement on blood lipids, haemostatic variables, bleeding time and plasma vitamin A and carotene were studied. In seven subjects platelet aggregation induced by adenosine 5′-pyrophosphate (ADP) was also studied.
2. The proportions of 20:5ω3 and 22: 6ω3 in platelet and erythrocyte phosphoglycerides were substantially increased by the supplement mainly at the expense of ω6 polyunsaturated fatty acids.
3. Mean plasma triglyceride concentrations were reduced and those of high-density-lipoprotein (HDL) cholesterol were increased by the supplement.
4. The mean bleeding time was significantly prolonged after 3 weeks of taking the supplement, but had returned to the presupplementation value 5 weeks after withdrawal of the supplement.
5. The maximum estimated response to platelet aggregation induced by ADP was increased by the supplement.
6. The mean levels of antithrombin III (immunological) and blood pressure were lower at the end of the period of supplementation and remained so 5 weeks after withdrawal of the supplement. No significant changes in other variables were noted.