274 



THE BIOCHEMISTRY OF B VITAMINS 



been content to neglect the exceptional individual whose performances 

 are out of line. Even information regarding the average man has been 

 difficult to obtain." 



"Casual information suggesting individual variability in vitamin re- 

 quirements is readily available. Probably every doctor who deals in his 

 practice with vitamin requirements could cite cases of unusual benefits 

 from vitamins, or cases in which administration of a vitamin was effective 

 in one case and wholly ineffective in another." 



Figure 1. 



.6 .8 1. 



REQUIREMENT 



1.6 



1.2 1.4 



IN MC/OAY 



Distribution of the daily thiamine requirement among fifteen individuals. 



Actual cases of individual variations might be enumerated in great 

 length. In some, the variability may be extreme. For instance, even when 

 all presently recognized vitamins are added to the diets of chicks it is 

 known that a certain small percentage of them (about 2 per cent) still 

 develop perosis. 49 Bloomfield 50 found great variation in the weight losses 

 among rats on deficiency diets, and found that after recovery, the same 

 individuals again lose the most weight on a second test on the deficiency 

 diet. 



Berryman et al. 51 have come across the same problem in B vitamin 

 excretion studies, finding that different human individuals, even under 

 the best controlled conditions, may still excrete widely varying amounts 



