January 31, 1974
It can be concluded that the native [Eskimo] diet, despite its remarkably restricted composition, is capable of furnishing all the nutrients essential for nutritional health, provided it is available in adequate amounts and is prepared according to traditional methods.
The Aboriginal Eskimo Diet in Modern Perspective
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The aboriginal diet of the Arctic Eskimo, which consisted mainly of land and sea mammals and fish, is analyzed with respect to its capacity to provide the nutrients now regarded as essential for nutritional health. It is concluded that, despite its remarkably restricted composition, the native diet is capable of furnishing all the essential nutritional elements when prepared and consumed according to traditional customs. However, its low carbohydrate and high protein content necessitated major metabolic adaptations in energy and nitrogen metabolism. Erosion of the traditional diet culture and life style has been accompanied by a decline in nutritional status. [Eskimo, diet, nutrition]
A natural association between the “B complex” vitamins and proteins in the enzyme systems of animal tissues provides strong assurance against a deficiency of these vitamins in a diet high in animal protein. There is no history among Eskimos of the epidemic vitamin deficiency diseases which afflicted some cereal-based food cultures. The oils of fish and marine mammals are rich in the fat-soluble vitamin A and D. A high meat diet also provides adequate amounts of vitamin K. The vitamin E nutriture of Eskimos is of particular interest, since this vitamin is ordinarily derived mainly from cereal oils. A recent investigation of the vitamin E status of Alaskan Eskimos revealed that their blood levels are fully comparable to those of populations consuming a mixed diet (Wo and Draper 1975). This finding is attributable to the fact that nearly all of the vitamin E in animal tissues is present in its most active form (a-tocopherol), whereas in cereals it is present primarily as a less active isomer (7-tocopherol).
Stefansson’s appraisal of the ascorbic acid nutriture of the Eskimo has successfully withstood 40 years of critical evaluation, namely “. . . that if you have some fresh meat in your diet every day, and don’t overcook it, there will be enough C from that source alone to prevent scurvy” (Stefansson 1935-36). The Eskimo practice of eating their food in the raw, frozen, or lightly cooked state was a critical factor in preserving the small amounts of vitamin C necessary to prevent scurvy (less than 10 milligrams per day).
The predominant feature of the Eskimo native diet from an adaptational standpoint is its remarkably low carbohydrate content. The all-meat diet typically provides about 10 grams of glucose in the form of glycogen per 2,500 calories.
A subject of frequent speculation concerning the energy metabolism of Eskimos is whether they relied on ketone bodies as a significant source of metabolic fuel. It is difficult to estimate how frequently conditions conducive to ketogenesis prevailed in Eskimo dietary experience, but it seems likely that there were times when the supply of protein was inadequate to meet the amino acid requirements for glucose synthesis as well as for protein synthesis. Further, it has been estimated that the capacity of the liver to convert amino acids to glucose is limited to about half the total energy requirement. Four of the 20 amino acids supplied by dietary protein are ketogenic as well as glycogenic and anQther (leucine) is specifically ketogenic. An abrupt change from a mixed diet to a meat diet leads to asymptomatic ketafis and ketonuria, but these conditions gradually diminish as a result of biochemical adaptation to the use of ketone bodies for energy. Whether Eskimos have unusual adaptational capabilities in this regard is unknown.
Their high-protein diet imposed on Eskimos a need to dispose of an unusually large metabolic load of urea, a potentially toxic nitrogenous compound formed during the conversion of amino acids to glucose. Animals fed high-protein diets exhibit diuresis and an increase in water consumption, and it is of interest that early explorers commented on the high water intake of Eskimos. A feedback mechanism acts to prevent uremia under conditions of high protein intake by stimulating water consumption and thereby enhancing the dilution and excretion of urea. The need for efficient urea clearance implies that renal disease in Eskimos consuming the native diet has unusually serious clinical implications. The all-meat diet is also distinctive with respect to its lack of “fiber,” a composite of plant materials which is resistant to digestion and therefore passes relatively unchanged into the feces. Such materials normally exert several physiological effects, including an enhancement of food transit through the gut, an increase in fecal bulk, alterations in bacterial activity, and a sequestering of cholesterol and bile salts. The decline in the fiber content of the general U.S. dietary in recent decades has been implicated as a factor in the incidence of a number of intestinal diseases (constipation, diverticulosis, colonic cancer) which may be increased by food stasis and putrefaction in the lower intestine. Medical records are too fragmentary to indicate whether these diseases are unusually prevalent in Eskimos habituated to the native diet.
The modem Eskimo has for the first time the opportunity to make significant food choices. Presented with an array of exotic new foods which he is not equipped by personal experience or education to evaluate, he tends to choose badly. In general, the items he selects are below the average quality of the U.S. mixed diet and of the foods they replace in his native diet. His nutritional status is deteriorating, in terms of both undernutrition and overnutrition, in direct relation to the proportion of processed foods in his total diet. In the subarctic, where dietary acculturation is extensive, the Eskimo has the full complement of diet-related diseases that are characteristic of other segments of the U.S. population of low socioeconomic status: obesity, cardiovascular disease, hypertension, and tooth decay.
Acknowledgment. This paper was presented at a symposium on Human Adaptability in Relation to Regional Ecosystems held under the auspices of the International Biological Program at the 141st annual meeting of the American Association for the Advancement of Science, New York City, 26-31 January 1974. The author gratefully acknowledges the collaboration of the following: R. Raines Bell, J. G. Bergan, Catherine C. K. Wei Wo, G. V. Mann, L. M. Hursh, M. J. Colbert, and Christine A. Heller.