Carnivore Diet

Introduction. 

With the increasing human activities in circumpolar areas in recent years, the problem of an adequate and physiologically suitable ration with high caloric density has been the subject for much dispute among physiologists and nutritionists. Although a high protein diet has been successfully used by Eskimos and arctic travellers for generations, both as trail diet and emergency rations, there has been a tendency in recent years to emphasize the desirability of an all-carbohydrate ration ( Mellinger, 1948, Roth, 1948, Dyme, 1950). One of the main arguments in favor of the carbohydrate ration has been its antiketogenic effect, assuming harmful effect of slight ketosis even during the short periods of survival in question under arctic conditions. 

With reference to these questions a study was designed, the purpose of which was to consider a high-carbohydrate versus a high-protein diet, with reference to physiological adequacy and an evaluation of the physiological and clinical significance of ketosis under strenuous arctic field conditions during midwinter in Alaska. 

4. Discussion. 

It is clearly realized that the determination of ketone bodies is subject to considerable inaccuracy. However, the reported data indicate that under the conditions of the test the excretion of urinary acetone in the meat group never exceeded 1 g per day. The highest figure recorded was 8 66 mg which is a very small amount. 

According to Peters and Van Slyke (1946), ketones are regularly found in the urine of healthy persons leading a normal life. Van Slyke found as much as 280 mg ketones per 1000 ml urine. Others have reported figures between 7 and 125 mg daily. 

Under conditions such as total starvation when all energy is derived from protein and fat, the production of ketone bodies by the liver is accelerated and the excretion of ketones in the urine increases. In normal adults the appearance of gross ketonuria, according to Peters and Van Slyke (1946), does not reach its height until 3 to 5 days of the fast have elapsed. As starvation proceeds ketosis gradually diminishes. He states that in the normal male, ketosis of starvation does not reach serious proportions because sufficient carbohydrate is derived from protein and oxidized, and the levels of blood ketones are not high enough to tax severely the mechanism for the preservation of acid-base equilibrium. In one subject about 6 g of ii-hydroxybutyric acid were excreted daily in the urine for the last two weeks of a 31-day fast. In diabetic acidosis ketonuria may reach values 10 times higher than this. 

Compared with these figures the amounts of acetones excreted in the urine in our subjects on the meat ration are insignificant, and it appears that this slight ketonuria observed under these conditions for the periods considered likely as the duration of a survival situation would have no appreciably harmful effect. 

Exercise greatly increases the ketosis, and a 10-mile walk in the morning without breakfast will produce distinct ketonuria in a healthy person who otherwise is living on a normal diet (Courtice and Douglas, 1936). 

A number of evidences indicate a mechanism of adaptation to ketosis. In our Eskimo studies it is observed that the degree of ketonuria is less than what is normally observed in Whites on a similar diet. On the other hand, an Eskimo soldier who had lived for several months on the normal Army mess rations excreted the same amounts of acetone as the normal white soldiers when given a "ketogenic" diet. In the subjects studied by McClellan and DuBois (1930) the ketonuria diminished after several months on a carbohydrate-free diet. 

Deuel and Oulick (1932) have demonstrated that ketosis develops more rapidly and attains greater intensity in women than in men. 

It has been repeatedly observed that ketosis frequently occurs under strenuous field conditions regardless of the diet, and Sargent and Consolazio (1951) showed that the ketosis is reduced when the same subject undergoes repeated field tests, indicating some evidence of adaptation. 

In an Arctic bivouac at Fort Churchill the approximate caloric expenditure was 4000 calories per day. The caloric intake was about 3600. Under these conditions all the men showed trace quantities of urinary ketones almost every day, starting on the third day in the bivouac (Molnar et al., 1942). 

Of the great variety of physical fitness tests (Cureton, 1947), the Treadmill Test was selected for practical reasons. It should be emphasized, however, that physical fitness is exceedingly difficult to evaluate, not only because the meaning of physical fitness is far from clear, but also because the result of the test is greatly dependent upon a number of factors beyond the control of the observer. 

In all cases we observed an improvement at the end of the field phase, most marked in the carbohydrate group, associated with approximately 10-pound weight loss (7.5 %). 

It should be noted that the subjects had been living on a caloric deficit of the order of 2000 calories a day, and performing daily route marches of 10 miles. 

In the case of untrained personnel in poor physical condition, one would expect an improvement in physical fitness during the field phase. Our subjects, however, were all well trained and in excellent physical condition at the onset of the experiment. The factor of physical training therefore can hardly explain the difference in the physical fitness scores. 

On the other hand, it appears that the weight loss may be the most important factor in explaining the observed difference. The subjects started off probably slightly overweight and the loss of 7 per cent of their body weight would tend to increase their physical performance, since there is less weight to carry during the exercise. This is in conformity with general experience under similar conditions. It is observed that the carbohydrate group, which had the greatest weight loss, also showed the greatest improvement of physical fitness scores. The purpose of the experimental phase was to study the effect of the experimental diet on various physiological functions as compared with the levels during the normal conditions in the standardization phase. The results indicate the following effect: Both in the carbohydrate group and in the meat group, there was an increase of the physical fitness scores, most pronounced in the carbohydrate group. The basal heat production was 13 per cent higher at the end of the experimental phase than during the standardization phase in the meat group, while a reduction of 7 per cent occurred in the carbohydrate group. This difference is probably due to the specific dynamic action of protein. During the experimental phase the meat group consumed 300 ml more fluid per day than the carbohydrate group. While all subjects in the meat group were in a positive nitrogen balance, the subjects in the carbohydrate group showed a negative balance of 6.3 g on an average. Ketonuria occurred in all meat subjects and in three of the carbohydrate subjects. 

During the field phase the factor of climatic stress was added to the experimental conditions, and the following results were obtained: 

No significant difference was observed in the physical performance of the subject on the meat ration, the carbohydrate ration, or on the meat-and-carbohydrate ration during the actual field phase. The physical fitness scores were improved in all three groups at the end of the field phase, and this improvement was greatest in the carbohydrate group which also had the greatest weight loss. The psychiatric evaluation revealed no distinct differences between the three groups. There was no significant deterioration in morale, but an increase in carelessness, irritability and desire to sleep which occurred in all three groups. The weight loss was 7.0 per cent in the meat group, 7.5 per cent in the carbohydrate group, and 6 per cent in the group receiving both meat and carbohydrate. There was an increase in the basal heat production of 9 per cent in the meat group and 7 per cent in the meat-carbohydrate group, while the carbohydrate group showed a reduction of 7 per cent in the BMR. The water consumption was 1500 ml in the meat group, 850 ml in the carbohydrate group, and 1200 ml in the meat-carbohydrate group. All three groups showed negative nitrogen balance, which was most pronounced in the carbohydrate group, where it was approximately 7 g, as against approximately 2 g in the meat group. Ketonuria occurred in all three groups, most pronounced in the meat group. 

On the basis of these findings, and in view of the fact that water supply, as a rule, does not present any problem in the Arctic, it may be concluded that the carbohydrate ration offered no significant advantage under conditions of arctic survival as stimulated in the present study. In terms of heat production and nitrogen balance, the high meat ration is preferable. It is evident from this study that under survival conditions, which necessitate caloric expenditure, between 2500 and 3000 calories per man per day, including travel of approximately 10 miles a day, 1000 calories per man per day is sufficient for a period of at least 10 days. 

It would therefore seem logical that survival rations developed for arctic use should consist of protein, fat, and carbohydrate in proportions which would serve to utilize the specific dynamic action of a high protein diet, the high caloric density of fat, and the physiological advantages of carbohydrates. Protein-fat rations with high caloric density such as various types of pemmican, have already been successfully used for more than half a century by arctic travellers. 

It would appear advisable to base future arctic survival rations on the principle of a high meat-fat ration as the main meal of the day prepared in the evening, and an all-carbohydrate component of the ration to be consumed in the middle of the day while on the trail. 

5. Summary and Conclusions. 

In a series of laboratory experiments followed by field experiments under strenuous arctic conditions, the physiological adequacy of low caloric arctic rations have been studied in groups of normal men under conditions which necessitate travel under various arctic conditions. The rations studied contained approximately 1000 calories per man per day and consisted of an all-carbohydrate ration and a high protein-fat ration. On the basis of the presented data it may be concluded that from a physiological standpoint the all-carbohydrate ration offered no significant advantage over the high meat ration under the conditions of the study.

4. Discussion. 

Since hypertension in man has been stated to be typically associated with increased incidence and severity of atherosclerosis (Katz and Stamler, 1953), it would be of interest to compare the incidence of hypertension in Eskimos with that of Whites although the interrelationship between hypertension and atherosclerosis is by no means clear. In a survey of 104 Alaskan Eskimos the author found that both the systolic and diastolic blood pressures were lower in Eskimos than in Whites of corresponding age. Eighty per cent of the recorded systolic blood pressures were below 116 mm Hg. and no systolic blood pressure higher than 162 mm was ever recorded in our "normal" Eskimo subjects. In a series of 117 Eskimo patients, only one of the patients had systolic blood pressure above 145 mm (a 60-year old woman having a blood pressure of 200/80 mm) (Rodahl, 1954). It may be noted in this connection that Alexander (1949) found hypertension to be practically non-existent among Aleuts, and his electrocardiographic and clinical examination of 296 Aleuts, including 23 above the age of 60, revealed almost no cardiovascular disease. 

Gotman et al. (1950) have found that some hypertensives show elevated plasma concentrations of Sf 10-20 lipoproteins even if the blood cholesterol concentration is normal, although these changes in the "giant molecule" levels are not correlated with the degree of hypertension. 

Very little is known regarding the plasma lipids in Eskimos, and the plasma lipid studies in Eskimos so far reported have yielded inconsistent data. This may not be surprising when considering the wide range of conditions, dietary and otherwise, encountered in the different groups of Eskimos. Corcoran and Rabinowitch (1937) who studied two groups of Canadian Eskimos, one group subsisting on a meat diet and one group subsisting on a mixed diet, found in both groups lower concentrations of plasma lipids and of cholesterol than the normal values for Whites, and the meat group had slightly higher plasma lipid levels than the group on a mixed diet. In this connection it may be noted that serum cholesterol in Whites is decreased in severe caloric undernutrition (Keys, 1953-b). Periods of semi-starvation may occur among the Eskimos, which thus may affect the blood lipid levels. Sinclair et al. ( 1949) have reported plasma lipid findings in the Canadian Eskimos that are similar to the figures considered normal in Americans. Wilber and Levine (1950) found moderately elevated plasma lipid levels of Alaskan Eskimos. It may also be noted that Alexander (1949) found mean plasma cholesterol levels of 176-197 mg/l 00 ml in two groups of Aleuts. 

In view of the small number of Eskimos examined in the present study no definite conclusion can be drawn from this limited material. These preliminary investigations indicate, however, that while some Eskimos, such as the Nunamiuts, may have very high cholesterol intakes, the average figures for dietary cholesterol and fat for the four Eskimo groups examined are comparable to those of the average American man; their blood cholesterol levels are the same, while the Sf 12-20 lipoproteins (Gofman fraction) were lower in concentration than Whites of corresponding age. If it were convincingly demonstrated that the Eskimos in reality have a lower incidence of cardiovascular disease than Whites, it would appear that these findings support Gofman's postulates that the high concentration of the cholesterol-bearing protein molecules are associated with atheroclerosis. 

It should be noted, however, that very little exact information is available regarding the occurrence of arteriosclerosis in Eskimos. None of the 16 Eskimos analyzed here showed any evidence of arteriosclerosis by clinical or roentgenological examination, and cardiovascular disease was extremely rare among the large number of Eskimo patients examined by the author during a two-year period in Alaska. Similarly, Dr. Paul Haggland, who has operated on a large number of Eskimos in Alaska during the last 15 years, has never seen arteriosclerosis or atherosclerosis in Eskimos (personal communications). He had the occasion to perform autopsy on one female and two male Eskimos, aged 60-65 years, and found no arteriosclerosis. Dr. Earl Albrecht, Territory Commissioner of Health, states that arteriosclerosis is rare in Eskimos, based on clinical evidence (personal communications). 

Bertelsen (1940) is, on the other hand, of the opinion that arteriosclerosis is fairly common in Greenland, particularly if one considers the average span of life for the Greenland Eskimos. Hoygaard (1941) writes with regard to the Angmagssalik Eskimos, Southeast Greenland, that "arteriosclerosis was frequently found even in persons below 40". 

Brown (1951) states with regard to the Southampton Island Eskimos and the Igloolik Eskimos: "We have found well-marked general arteriosclerosis and also coronary heart disease proved by electrocardiogram and, in one case, by post mortem. Some of the cases of coronary heart disease were in congestive failure." 

During our study of the patho-physiology of the Alaskan Eskimos from 1950 to 1952, x-rays were taken of the chest and extremities of 84 Eskimos, using a portable x-ray apparatus. All chest x-rays were taken at a distance of 180 cm; all x-rays of the limbs (left arm and left leg) were taken at a distance of 90 cm. Professor Johan Torgersen, Institute of Anatomy, Oslo University, has very kindly examined all these roentgenograms, with a particular reference to possible roentgenological evidence of arteriosclerosis and other cardiovascular abnormalities. He finds, as a typical feature of all roentgenograms examined, that the bone structure in the Eskimo is unusually massive with sharply defined, well-calcified bone lamellae. The muscle attachments are as a rule very large. The occurrence of arthritis deformans is no less frequent in these Eskimos than in Whites of similar age (:5 cases in 84 Eskimos, 51 males and 33 females, with an average age of 28 years). Four Eskimo subjects at Barter Island had cartilaginous exostoses on the tibia (fig. 2). 

From this material (see Table 5) it appears that the occurrence of roentgenological evidence of arteriosclerosis in these Eskimos is neither more nor less than what one would expect to find in Whites of similar age groups. Out of 9 Eskimos over 47 years of age, roentgenological evidence of atherosclerosis of the arch of the aorta was detected in 3 cases, 2 males and 1 female. Of the entire material one Eskimo showed calcium deposits in the arteries (see fig. 1). In one 60-year old Eskimo woman with a blood pressurc of 200/80, thcre was slight enlargemcnt of the left ventricle of the heart. It is thus evident that further studies are necessary in order to settle the question of arteriosclerosis in the Eskimo and the relation between dietary cholesterol, serum cholesterol levels and cardiovascular disease ill these people.

5. Summary and Conclusions. 

The cholesterol content of some common Eskimo foods has been determined and the serum cholesterol level as well as the serum concentration of Sf 12-20 lipoproteins in 16 healthy Alaskan Eskimos are reported. On the basis of these preliminary data it appears that some Eskimos have high cholesterol intakes compared with healthy American men, but that their blood cholesterol levels are the same. On the other hand, the Sf 12-20 lipoproteins in Eskimos are lower in concentration than in Whites of corresponding age. From the available evidence it appears that the incidence of cardiovascular disease among the Alaskan Eskimos may be lower than in whites. A more complete analysis of this problem is in progress.

Updated version of Not by Bread Alone

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MANY different types of diet have been successfully used to reduce weight in those considered obese. The principle on which most of them are constructed is to effect a reduction of calorie intake below the theoretical calorie needs of the body. Experience with these patients has suggested, however, that this conception may be too rigid. Many of them state that a very slight departure from the strict diet which can hardly affect calorie intake, results in them failing to lose weight for a time. Though it is realised that evidence from such patients is notoriously inaccurate owing to their approach to this particular condition, it is too constant a belief among them to be entirely discarded. Furthermore, most of the diets in common use not only restrict the intake of calories but also radically alter the proportions provided by protein, fat, and carbohydrate. In this country a healthy sedentary person may be supposed to consume some 2200 calories daily, made up of about 70 g. of protein, 60 g. of fat, and 350 g. of carbohydrate : protein supplies 12% of the calories, fat 24%, and carbohydrate 64%. On most reducing diets, however, the carbohydrate and fat will be restricted while the protein remains about the same ; and in a diet yielding 1000 calories protein may provide 30%, fat 37%, and carbohydrate 33%. Finally, Lyon and Dunlop (1932) observed that patients on isocaloric reducing diets lost weight more rapidly when the largest proportion of the calories was supplied by fat than when it was supplied by carbohydrate. Anderson (1944) attributed these findings to the different amounts of salt (causing water retention) in the diets used by these workers. More recently, Pennington (1951, 1954) has recommended high-fat diets in the treatment of obesity. It therefore seemed important to establish which factor has the greater effectrestriction of calories, or alteration in the proportions of MANY different types of diet have been successfully used to reduce weight in those considered obese. The principle on which most of them are constructed is to effect a reduction of calorie intake below the theoretical calorie needs of the body. Experience with these patients has suggested, however, that this conception may be too rigid. Many of them state that a very slight departure from the strict diet which can hardly affect calorie intake, results in them failing to lose weight for a time. Though it is realised that evidence from such patients is notoriously inaccurate owing to their approach to this particular condition, it is too constant a belief among them to be entirely discarded. Furthermore, most of the diets in common use not only restrict the intake of calories but also radically alter the proportions provided by protein, fat, and carbohydrate. In this country a healthy sedentary person may be supposed to consume some 2200 calories daily, made up of about 70 g. of protein, 60 g. of fat, and 350 g. of carbohydrate : protein supplies 12% of the calories, fat 24%, and carbohydrate 64%. On most reducing diets, however, the carbohydrate and fat will be restricted while the protein remains about the same ; and in a diet yielding 1000 calories protein may provide 30%, fat 37%, and carbohydrate 33%. Finally, Lyon and Dunlop (1932) observed that patients on isocaloric reducing diets lost weight more rapidly when the largest proportion of the calories was supplied by fat than when it was supplied by carbohydrate. Anderson (1944) attributed these findings to the different amounts of salt (causing water retention) in the diets used by these workers. More recently, Pennington (1951, 1954) has recommended high-fat diets in the treatment of obesity. It therefore seemed important to establish which factor has the greater effectrestriction of calories, or alteration in the proportions of protein, fat, and carbohydrate in the diet.

Discussion 

If these observations are correct, there seems to be only one reasonable explanation-namely, that the composition of the diet can alter the expenditure of calories in obese persons, increasing it when fat and protein are given, and decreasing it when carbohydrate is given. This is not surprising as regards protein, whose specific dynamic action has long been recognised. It is, however, surprising as regards fat, whose action in this respect seems to be even greater than that of protein. Direct confirmation of such altered metabolism is hard to obtain. The B.M.R., for example, is measured at a time of day and under .other conditions specifically designed to eliminate the effect of diet or reduce it to a minimum. In some patients the B.M.B. was measured at the beginning and at the end of each dietary period. Table vin shows that neither variation in calories nor variation of the composition of the diet with a constant intake of calories significantly changed the B.M.R. during these short dietary periods.

Summary 

1. Loss of weight can be successfully achieved in obese patients by numerous diets, most of which restrict calorie intake. At the same time almost all such diets alter the proportion of protein, carbohydrate, and fat as compared with the normal, restricting carbohydrate and fat in particular. It seemed desirable to investigate which factor was of the greatest importance in weight reduction-calorie restriction or alteration in the composition of the diet. 

2. The rate of weight-loss has been shown to be proportional to the deficiency in calorie intake when the proportions of fat, carbohydrate, and protein in the diet are kept constant at each level of calorie restriction. 

3. When calorie intake was constant at 1000 per day, however, the rate of weight-loss varied greatly on diets of different composition. It was most rapid with high-fat diets ; it was less rapid with high-protein diets ; and weight could be maintained for short periods on diets of 1000-calorie value given chiefly in the form of carbohydrate. 

4. At a level of intake of 2000 calories per day, weight was maintained or increased in four out of five obese patients. In these same subjects significant weight-loss occurred when calorie intake was raised to 2600 per day, provided this intake was given mainly in the form of fat and protein. 

5. No defect in absorption of these experimental diets occurred to account for the weight-loss. There was neither loss of body-protein stores nor of carbohydrate stores to a degree which significantly contributed to the reduction in weight. 

6. The weight lost on these diets appeared to be partly derived from the total body-water (30-50%) and the remainder from body-fat (50-70%). 

7. As the rate of weight-loss varied so markedly with the composition of the diets on a constant calorie intake, it is suggested that obese patients must alter their metabolism in response to the contents of the diet. The rate of insensible loss of water has been shown to rise with high-fat and high-protein diets and to fall with highcarbohydrate diets. This supports the suggestion that an alteration in metabolism takes place.

"The great progress in dietary control of obesity, was the recognition that meat . . . was not fat producing; but that it was the innocent foodstuffs, such as bread and sweets, which lead to obesity."