266 THE BIOCHEMISTRY OF B VITAMINS 



an individual, except as these factors influence the calorific intake. Thus, 

 for a given species, the requirement expressed as the vitamin-to-calorie 

 ratio is independent of the weight of the individual. General considera- 

 tions would indicate that this is similarly true for the other B vitamins, 

 and it is possible that this constitutes a distinguishing characteristic of 

 the B group. 



Unfortunately, little work has as yet been done on the effects of age, 

 as distinguished from weight, on B vitamin requirements. Rafsky and 

 Newman 9 > 10 have studied the niacin requirement of the aged, and more 

 recently their thiamine excretion. 11 A study was made of 31 persons, 14 

 men and 17 women, ranging from 65 to 81 years of age and on adequate 

 thiamine intakes (0.51-1.11 mg/day). Forty-five per cent of the subjects 

 were found to excrete less than 50 y per day of thiamine, which is con- 

 siderably below the generally accepted normal value. Despite the fact 

 that a similar percentage of the group had a low gastric hydrochloric 

 acid secretion and six had total achlorhydria, this was not correlatable 

 with the low thiamine excretion. Mills et al. 12 have recently shown that 

 the thiamine requirement of adult rats per gram of food increases greatly 

 with old age and increasing weight. Since in the aged the caloric require- 

 ments may be much less than in younger individuals, these would seem 

 to be findings of great significance. The presumption that in old age the 

 efficiency of vitamin utilization is greatly curtailed would seem to be of 

 considerable theoretical interest to the growing field of geriatrics. 123 



In the extremely young, the situation is somewhat more lucid. In 

 children from one to ten years there is a gradual increase in caloric 

 requirement with age, and the B vitamin requirements parallel this. 13 

 This is not to say that extraneous factors may not influence the require- 

 ment in young individuals and then become insignificant later. Thus, 

 Schweigert et al. 14 found that young mice were much more sensitive to 

 the influence of protein levels on the niacin requirement than were older 

 ones. A variety of similar observations will be discussed at later points 

 in our studies. Suffice it to say that much of our knowledge of B vitamin 

 requirements has been derived from experiments upon adults, and much 

 remains to be learned before this can safely be extrapolated to the very 

 young and the very old. 



Influence of Sex. The influence of sex on the B vitamin requirements, 

 so far as is now known, is exerted by virtue of the known differences in 

 basal metabolism and caloric intake between the sexes, and the increased 

 requirement during reproduction. Up to five years, the average caloric 

 intakes of boys and girls are the same, and this appears true of the B 

 vitamin requirements also. Subsequently, however, boys have a higher 

 caloric intake and therefore a higher requirement for B vitamins. 13 Here 



