METHODS OF ASSESSING B VITAMIN REQUIREMENTS 



253 



Table 3. Classification of Diets in Table 2 as to Thiamine Deficiency. 

 Thiamine Gig /day) 



Table 4. Vitamin Bi Content of Diets of Families of Wage Earners and Low-Salaried 

 Clerical Workers. 



Region, number of families 



North Atlantic, 1394 white families 



Pacific: 688 white families 



East South Central : 426 white families 



South: 284 Negro families 



Sherman — Average American Diet 



(Cowgill p. 186) 

 American Family on Food Relief 



(Cowgill p. 194) 

 Assumed boderline for clinical beriberi 



276) doubtless contributing a somewhat greater element of safety than is 

 apparent in these lower values. 



Goldberger's classical studies on the nicotinic acid requirement of man 

 are likewise of a survey nature. Frazier and Friedemann have recently 

 re-evaluated these studies, including the dietary records of some 1863 

 human subjects 30 and concluded on this basis that the human require- 

 ment for nicotinic acid, when other factors are present in good supply, is 

 about 4 mg/day, but may be as high as 7.5 mg/day on a marginal diet 

 high in corn products. Similarly, Williams 31 studied the B vitamin con- 

 tent of mixed human diets known to be adequate for human nutrition, of 

 a highly satisfactory animal ration, and of a rat carcass, and found them 

 highly similar on an isocalorific basis, as is shown in Table 5. He con- 

 cluded, therefore, that these values probably indicate "safe" levels for 

 a daily human intake. 



