The effect of cod liver oil in two populations with low and high intake of dietary fish

Two subgroups of healthy males from an inland and a coastal community in Norway with a traditionally low and high consumption of dietary fish were given a dietary supplement of 20 ml cod liver oil rich in n-3 polyunsaturated fatty acids for 3 weeks. Cod liver oil induced an increase in serum high density lipoprotein (HDL) cholesterol in men from the inland. Both groups showed a prolonged primary bleeding time, whereas platelet aggregation and thromboxane A2 production induced by collagen were mainly unaffected. Platelet phospholipid fatty acids showed similar changes in both groups with a decrease in n-6 and an increase in n-3 polyunsaturated fatty acids. No changes were observed in total cholesterol or platelet phospholipid content. This study shows that dietary supplement with cod liver oil induces changes in serum lipids and platelets that may reduce the tendency to thrombosis both in subjects with a low and in those with a high intake of dietary fish. The effects were more pronounced in the subjects with a traditionally low fish consumption.