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NON-ENERGETIC POWERS OF NUTRITION HANS KAUNITZ, M.D.* The energy content of foods has played an important part in clinical nutrition. New observations suggest that emphasis is shifting to more concern with the qualitative properties offoodstuffs; so it is timely to consider some ofthe new developments and to speculate about future experiments . Under the influence of the German school of the nineteenth century, stress was upon the role offood as a provider ofcalories, to the neglect of other properties, which found expression in the isodynamic principle that foodstuffs can replace each other isocalorically. Non-caloric factors such as minerals and vitamins were thought to be necessary merely to complement certain systems, such as the enzymes—to be materials comparable to screws inan engine, which keep the mechanismtogether without changing its energetic aspects. Rich discoveries have been made on the basis of these theories, but it becomes more and more apparent that emotional, hormonal, and immunologic responses to food are very important—aspects which were not sufficiently appreciated under the energetic theory; neither has enough thought been given to the possibility of adaptive changes induced by nutrition. Man's attitude toward food can be reduced to two basic viewpoints. The older one, much less emphasized at present, holds that variations in the dietary regimen can produce far-reaching physical and mental changes. An example is vegetarianism, which has a history ofseveral thousand years and is the most frequently found form of voluntary dietary restriction. The belief that vegetarianism improves body and mind has stubbornly persisted; and use oflow-protein diets, preference for vegetable oils, and employment oflow-salt regimens indicate that we are returning to some * Institute ofComparative Medicine, Columbia University College of Physicians and Surgeons. 75 of its principles. Frequendy vegetarianism has been associated with the amount as well as the kind of man's food. Man tends to overeat but has always been aware of the evil consequences of this habit. Today we observe that thin rats live longer than fat ones (i). The other viewpoint is that the body can be nourished by a wide variety ofbalanced diets and that variations in the "balanced" diet demand few, if any, bodily adjustments. It is expressed in the Hippocratic work on dietetics (2): In the human body, there is perpetual exchange. Minute particles ofeverything that exists in nature are to be found in the tissues. Heat and water continually interchange. Some parts take up, others give up, material; and during this process, more or less energy is being expended. Without food, there can be no growth. It is essential, therefore, that food which will serve as die diet ofman should possess all the characteristics ofthe human tissues. It is evident that the thinking ofmany present-day nutritionists is shaped by Hippocratic ideas. The belief in the power of food to bring about long-term bodily changes is given much less attention. I. The Value ofa Calorie The isodynamic principle not only states that carbohydrates, proteins, and fats can isocalorically replace one another but also implies that the caloric needs ofpeople ofthe same weight doing the same work are similar and that weight losses or gains will occur in accordance with the caloric intake. This viewpoint, implying that the value ofa calorie is more or less the same for anyone, is essentially that held by most nutritionists today and is the basis ofdietary recommendations for obese people. However, recent work has shown that the relationship ofcaloric intake to weight is infinitely more complicated. When the food intakes ofnormal and obese children were measured in an English institution, no caloric differences were found (3). When obese humans who maintained a constant weight of 225 pounds on 3,500 calories were placed on a 1,500 calorie diet, they lost 45 pounds and then maintained their weight at 180 pounds on the 1,500 calories. The work of 7 calories at 225 pounds was done by 3 calories at 180 pounds (4). Similar results have been observed with animals. Rats allowed a constant, restricted food intake first lost and later gained weight (5). When their food intake was restricted to just maintain their weight, their food requirements gradually declined, and 76 Hans...


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