270 THE BIOCHEMISTRY OF B VITAMINS 



All the patients in this study seemed quite normal and gave birth to 

 normal and well-nourished children. Since normal adults on well-balanced 

 diets containing about 0.86 mg. of thiamine per day excrete more than 

 200 fig of thiamine per day in the urine, 32 it would seem from this study 

 that there is little justification for the widespread vitamin supple- 

 mentation of the diets of pregnant women. Beyond this, however, there 

 is little information on the problem at hand, since the women were all 

 on ample diets and it is not possible to say how much their food intake 

 varied during the course of pregnancy. 



Table 10. Average 24-hr. Thiamine Excretion (^g) During Pregnancy. 



Group I Group II Group III 



Trimester Well-balanced Same diet + 0.75 mg Same diet + 1.50 mg 



diet only thiamine/day thiamine/day 



1 286 428 



2 263 620 932 



3 249 483 1131 



Kennedy and Palmer, 33 from studies on sows and on rats on egg-white 

 diets, have concluded that biotin is needed early in the life of the fetus, 

 and also later for normal lactation. The existence of a high biotin require- 

 ment in rapidly growing tissue is not entirely unexpected in view of its 

 biochemical function (p. 170). 



During lactation the B vitamin requirement remains high, since it still 

 represents the requirement of two or more individuals. When lactation 

 is possible, but for some reason does not occur, any increased vitamin 

 requirement is imperceptible. Apparently, the extent of the increased 

 requirement during pregnancy and lactation is not the same for each 

 vitamin. Thus, rats normally require about three times as much panto- 

 thenic acid as pyridoxine, but during lactation the ratio increases to six 

 times or higher. 34 



A number of factors work to raise the requirements during lactation, 

 chief among these being the fact that the physiological requirement of 

 the mother is now logically an amount such as will provide a sufficient 

 level in the milk to nourish the infant. It is quite clear that the thiamine 

 level in the milk is largely dependent upon the amount in the diet (p. 347) . 

 Therefore, a large increase in dietary intake might conceivably be neces- 

 sary to provide a sufficiently high level in milk. Rats are stated to require 

 five times the maintenance amount of thiamine to nurse a litter success- 

 fully. 35, 36 For these reasons the study of increased B vitamin require- 

 ments during lactation received quite early attention, 37 although little 

 scientific elucidation occurred until recent years. 



Roderuck et aL 3S have recently made excellent studies of the thiamine 

 and riboflavin requirements of humans during lactation. Fourteen women 

 were studied for an extended period during which analyses were made 



