282 THE BIOCHEMISTRY OF B VITAMINS 



concerns the fat-soluble group, it has been reported that the thiamine 

 requirement of the rat is considerably increased (as indicated by loading 

 tests) in vitamin A deficiency, and that large doses of thiamine delay the 

 appearance of symptoms of avitaminosis A. 92 



While rats are normally not susceptible to nicotinic acid deficiency, it 

 has been reported that a multiple deficiency of nicotinic acid, pantothenic 

 acid, and p-aminobenzoic acid produces a syndrome similar to that of 

 pellagra. While all these factors are required for its cure, 93 nicotinic acid 

 alone can delay the symptoms. There is at present a rapidly increasing 

 body of evidence which indicates that nicotinic acid and folic acid are 

 intimately associated in some manner in the cure of the symptoms of 

 nicotinic acid deficiency. 94 This problem is more appropriately discussed 

 in later chapters (pp. 408 and 412) . 



There is at present little explanation for the observation that thiamine 

 and cholic acid substitute for pantothenic acid in the Hall strain of 

 Clostridium botulinum Type A. 95 



Nutritional Customs, Habits, and Taboos. Of great practical concern 

 to the nutritionist is the problem of dietary habits and their effect on 

 nutritional requirements. Generally the effect of such habits is exerted 

 through obvious means (excessive carbohydrate intake, high protein diets, 

 high raw egg intake, etc.), but subtle factors may also be at work which 

 may influence dietary calculations to a considerable degree. Thus even 

 drinking water may contain appreciable quantities of B vitamins, and the 

 consumption of excessive quantities of coffee with its relatively high 

 trigonellin content might certainly influence the nicotinic acid requirement 

 (p. 288) . The habit of the Mexican natives of consuming beans with their 

 tortillas undoubtedly prevents widespread pellagra in Mexico. Such fac- 

 tors should then influence the calculation of adequate dietary require- 

 ments as much as they influence the adequacy of the diet itself. While it 

 is necessary to abbreviate what might well be an extended discussion on 

 this point, it is none the less important to emphasize the fundamental 

 nature of sociological aspects in assessing nutritional requirements. 



The Processing of Foods. Whereas the vitamin requirements of an 

 individual might well be met on the basis of the native vitamin content 

 of the diet, the situation may well be otherwise by the time the dietary 

 components have been marketed, stored, canned, cooked, baked, or other- 

 wise modified by circumstances of time, temperature, and chemical treat- 

 ment. Losses of B vitamins in food preparation vary widely with the 

 food and the precise methods involved; there have been a large number 

 of studies and publications on this subject. The topic, however, does not 

 fall sufficiently within the realm of this monograph to merit a detailed 

 discussion. Moreover, the ready availability of extensive data on this 



