314 



DIET 



become only gross approximations appli- 

 cable to the "average man," at best. 



Psychologically, the animal studies suffer 

 from serious limitations. One might reason- 

 ably ask, "How much information about the 

 influence of diet on special senses, motor 

 and intellective performance and personal 

 and social adjustment can be secured from 

 animal experiments?" Even when such ex- 

 periments can be carried out under ideal 

 conditions, how apphcable are such results 

 to man? It is highly doubtful whether work 

 with animals will ever answer such a ques- 

 tion as, "Why does a man refuse sausage, 

 giving as his excuse that it looks like horse 

 meat?" Man's appetite, food habits, and 

 preferences are conditioned by his individual 

 experiences and cultural patterns. Animal 

 experiments can shed little light on these 

 factors. 



The psychological alterations resulting 

 from dietary'- abnormalities usually appear 

 before any biochemical or physiological 

 changes can be detected. When experimen- 

 tal subjects were fed a diet that was very 

 low in thiamine, they early showed marked 

 changes in personahty and behavior (9, 26, 

 59, 60). Among the personnel on a sub- 

 marine who are exposed to many routine 

 "stresses," any dietary dissatisfaction may 

 have a very adverse affect on morale. It 

 matters little whether the complaints are 

 based on physiological or psychological 

 grounds. Actually, the subjective dissatis- 

 faction with the diet is far more important 

 than the question of nutritional deficiencies. 



In addition to the differences between 

 man and animals, and between different 

 animal species, the intra-species variabil- 

 ity should be taken into account more 

 seriously than it has been so far. Work 

 with different strains of rats has shown con- 

 siderable differences in the requirement for 

 such vitamins as riboflavin and thiamine 

 (39). Definite differences between normal 

 young men were observed in the urinary 

 thiamine excretions (47). Even though all 



of the subjects received the same vitamin 

 intake, there were some individuals who con- 

 sistently excreted two to three times as much 

 thiamine as others over the entire eight 

 months of the experiment. Do these dif- 

 ferences in vitamin excretion reflect some 

 profound physiological differences that es- 

 cape detection at the present time? 



With reference to the caloric intake, the 

 principle of individual requirement is well 

 recognized, the calories required being pro- 

 portional to the total body metabolism. In 

 connection with other dietary requirements, 

 such as those for vitamins and minerals, 

 the thinking is in general not so clear. Pett 

 (49) pointed out that dietary "requirements" 

 should not be indicated by a single value 

 but should be thought of and represented in 

 tables by the population mean and the "nor- 

 mal" range. The determination of dietary 

 requirements for a given person is, to a 

 certain extent, an individual, cUnical-experi- 

 mental problem. 



Methodology of Nutritional 

 Research 



Theoretical considerations as well as 

 actual experience in nutritional research de- 

 mand a multidisciplinary approach to the 

 study of human nutrition (10). In experi- 

 mental work where the social and cultural 

 factors are eUminated by being held "con- 

 stant," a combination of analytical and de- 

 scriptive techniques is required to define 

 precisely the nutritional regimen, as well 

 as the biochemical, physiological, and psy- 

 chological effects resulting therefrom. 



Laboratory nutritional research is 

 of necessity abstract and can study only 

 limited aspects of the total role that food 

 plays in man's life. The investigation of 

 such problems as food habits, preferences, 

 and aversions must extend to the home, the 

 school, the industrial canteen, the Navy mess 

 hall, etc. A combination of the techniques 

 of social psychology and cultural anthro- 

 pology in the study of food with reference 



