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DIET 



problems of submariners appeared. They 

 studied 1,489 patrol reports and, from the 

 comments of the commanding officers, made 

 various suggestions for improving the habit- 

 abihty of submarines. Their recommenda- 

 tions in many respects coincide with those 

 put forth in the present chapter. 



Physiologically, no acute nutritional prob- 

 lems exist as far as the submarine personnel 

 are concerned. The requirements for cal- 

 ories, vitamins, minerals, proteins, and other 

 foodstuffs appear to be the same as those 

 of other moderately active men. Conse- 

 quently, the improvement in submarine nu- 

 trition depends on general progress in the 

 physiological understanding of the role of 

 food in the overall metabolism of the human 

 organism and on technological developments 

 of food growing, preservation and prepara- 

 tion. 



It may be useful to point out some of the 

 physiological problems, important for sub- 

 marine nutrition but not strictly peculiar 

 to submarine conditions, which deserve the 

 attention of research workers. 



1. The relationship, between food and gas 

 production in the gastrointestinal tract is 

 one problem worthy of investigation. 



2. It is common experience that a heavy 

 meal is followed by drowsiness, yet we are 

 aware of no experimental investigations of 

 food intake and its influence on alertness. 

 It was found that taking even a moderate 

 meal by normal young men resulted in sig- 

 nificant changes in the electrocardiogram; 

 this indicates that the effects of meals cannot 

 simply be passed by as "subjective." The 

 submariner's eating is irregular and the 

 amounts are apt to be large. In the hmited 

 space he has no opportunity to "walk off" 

 a heavy meal. 



3. There is a hiatus in our knowledge of 

 the changes occurring, during prolonged 

 patrols, in food preferences, hkes, and dis- 

 hkes, and the over-all position of food in 

 the hfe of the submarine personnel. When 

 individuals are subject to confining and try- 



ing circumstance, some of them may find an 

 escape in eating. If this continues for any 

 length of time, it will eventually lead to the 

 development of obesity. On the other hand, 

 nervousness and anxiety may result in a 

 loss of appetite. This in turn may lead to a 

 loss of weight and a decrease in fitness. As 

 a means of checking these factors, it would 

 appear advisable to make determinations 

 of the weights of the men before and during 

 a long cruise. 



4. Body weight is a very gross measure of 

 "nutritional status." In this paper an in- 

 tegrated approach utihzing the techniques 

 of all the relevant sciences of man has been 

 emphasized. Additional work is required 

 in many areas before methods can be de- 

 veloped for the quantitative description of 

 the various facets of the human organism. 

 This is essential before the influence of nu- 

 trition can be studied. An example of such 

 a need is a method for the estimation of body 

 fat which requires Httle time and which does 

 not necessitate the determination of body 

 volume by weighing under water. 



5. In some fields the methods are satis- 

 factory but the proper physiological inter- 

 pretation of the data is not fully established; 

 the uncertainties concerning the significance 

 of urinary vitamin excretion values illus- 

 trate this point. 



6. Evidence has been presented that ani- 

 mal nutritional studies must be supple- 

 mented by experimental work with human 

 subjects. Even in those areas where species 

 differences are not questioned, it is difficult 

 to arrive at valid decisions on the quantita- 

 tive nutritional requirements of human be- 

 ings solely on the basis of animal studies. 

 This is true both for the amounts of the 

 different dietary nutrients required and the 

 length of time during which certain minimal 

 levels may be consumed before signs of a 

 deficiency appear. Reahstic nutritional re- 

 search is a costly proposition, but no cheap 

 substitute is available or possible. 



