The lifespan of the Greenland Eskimos is around 60 years of age, yet their death rate from ischaemic heart disease (coronary heart disease) is only around 3.5 %. This compared to the United Kingdom and the United States where ischaemic heart disease is the leading cause of death. The lipoprotein profiles of Eskimos are quite different to populations living in developed nations, with lower than average levels of triglycerides, low density lipoproteins (LDL) and elevated levels of high density lipoproteins (HDL). Analysis of fatty acid profiles of blood membrane lipids shows that Eskimos have much higher levels of omega-3 fatty acid than Western controls, and much lower levels of omega-6 fatty acids. In particular the omega-3 fatty acids eicosapentaenoic acid (EPA, C20:5 (n-3)) are relatively abundant in the membranes of blood cells, whereas arachidonic acid (AA, C20:4 (n-6)) was relatively scarce. It has been suggested that the low rates of ischaemic heart disease relate to these blood lipid profile.
Examinations of the diets of Eskimos living in Greenland have been performed in order to understand the reasons for these differences in disease risk and lipid profiles. For example, one group of researchers1 collected food samples from Eskimos for chemical analysis in order to investigate the intakes of various macronutrients. These values were then compared to those from Danish controls. The results showed that Eskimos consumed nearly double the amount of protein of the Danish controls, and this was offset by significantly less carbohydrate. Cholesterol intakes of the Eskimos averaged 264 mg/1000 kcal compared to 138 mg/1000 kcal for the Danes. Eskimos also had significantly lower intake of saturated fatty acids, a substantial higher intake of monounsaturated fatty acids and a slightly higher intake of polyunsaturated fatty acids. However, those polyunsaturated fatty acids that were consumed were predominately from the omega-3 class, which contrasted to the Danish diet where omega-6 fatty acids predominated.
The amount of omega-3 fat in the diet of the Eskimo was 13.7 grams per day per 3000 kcal, whilst the amount of omega-6 fat in the diet was 5.4 grams per day per 3000 kcal. Therefore the Eskimos diet provided an omega-6 to omega-3 fatty acid ratio of 1 to 2.5. In contrast the omega-3 fatty acid intake of the Danish diet was 2.8 grams per day per 3000 kcal and the omega-6 was 10 grams per day per 3000 kcal. Therefore the omega-6 to omega-3 fatty acid ratio of the Danish diet was 3.5 to 1. Current recommendations are that the omega-6 to omega-3 fatty acid ratio be around 3 to 1, which is very close to that achieved by the Danish diet. This recommendation is based on estimates of the traditional intake of omega-6 and omega-3 fatty acids from historic and nutritional records. Therefore the Eskimo diet appear to contain far higher concentrations of omega-3 fatty acids that are recommended for consumption. This may suggest that a certain degree of flexibility may exist in this ratio.
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