XIII. REQUIREMENTS AND FACTORS 587 



However, the validity of these recommended allowances has recently 

 received important confirmation from two sources. Frazier and Friede- 

 mann^" recalculated the nicotinic acid and other nutrients in diets known to 

 be pellagra producing or pellagra preventive, using dietary records gathered 

 by Goldberger and others. They concluded that the minimum daily intake 

 of nicotinic acid in a marginal diet containing corn products is about 7.5 

 mg. per day. More recently, Goldsmith and associates'"^ produced pellagra 

 experimentally in women with corn-containing diets which provided 4.7 

 mg. of nicotinic acid and 190 mg. of tryptophan daily. Other subjects who 

 received the same diet supplemented with 2 mg. of nicotinic acid, or 

 "wheat" diets providing 5.7 mg. of nicotinic acid and 230 mg. of tryptophan, 

 failed to develop pellagra. 



Much less precise information is available on factors which influence 

 requirements in man than in animals. Tryptophan can substitute, at least 

 in part, for nicotinic acid in human diets. The possible influence of corn 

 products (p. 548) and alcohol (p. 565) has been mentioned elsewhere. 

 Several factors are known which, chnically, seem to precipitate or predis- 

 pose man to attacks of pellagra. These are sunlight, heavy work, disturbed 

 gastrointestinal function, intestinal parasitism, and surgery. Whether these 

 increase requirements or act in an indirect manner is not established. Like- 

 wise, it is uncertain whether the peak incidence of pellagra in the early 

 spring months is due to the effect of sunlight, to increased exercise, or 

 simply to the development of a deficit of nicotinic acid during the winter 

 months. 



!»' G. A. Goldsmith, H. P. Sarett, U. D. Register, and J. Gibbens, J. Clin. Invest. 31, 

 533 (1952). 



