History and Epidemiology of Fish Oil in Man
Studies of Eskimo populations in northwest Greenland, where the economy has depended until recent years on whaling, sealing, and fishing, played a major role in raising the level of interest in dietary fish oils. A variety of anecdotal reports suggested that MI was rare in this isolated population. Visitors to the region had also long been aware of the frequent, prolonged episodes of epistaxis among the Eskimos.
Kromann and Green reported on a 25-year study of mortality and morbidity among approximately 1,800 Eskimos in the remote Upernavik district carried out between 1950 and 1974. Instead of the anticipated 40 cases of MI, they found only one. In another report, the death rate from MI in Eskimo men was estimated to be one tenth that of Danish men. website
Beginning in 1970, a series of Danish expeditions to the Umanak district of Greenland were led by Dyerberg and Bang. Their initial studies focused on plasma lipids, and the Eskimos were found to have somewhat lower cholesterol and triglyceride levels than Danish controls. Later studies analyzed the diet in detail, and it was found that the Eskimos consumed about 7 g/day of omega-3 fatty acids; approximately an order of magnitude greater than 10 times the amount eaten by Danes. Dyerberg and Bang then performed hemostatic studies in the Eskimos, which revealed a mild but definite prolongation of the Ivy bleeding time at 8.05 min vs 4.76 min in Danes (p<0.01). They also reported that incorporation of omega-3 fatty acids into platelets was associated with decreased platelet aggregation responses and a decrease in the platelet count (171 ± 59/cu mm vs 232 ±53 in Danes).
Working with Moncada and Vane, Dyerberg et al proposed a mechanism by which the omega-3 fatty acid EPA might alter the prostanoids generated by platelets and vessel walls, which could prevent thrombosis and possibly even atherosclerosis. Their initial studies were supported by the studies of Fischer and Weber, who demonstrated that: (1) the feeding of marine oils led to the formation of relatively inactive thromboxane A3 (TXA3) in human platelets and also reduced the formation of TXA2; and (2) that dietary fish oil led to the formation of PGI3 with biologic activity comparable to PGI2 in humans.