298 PYRIDOXINE AND RELATED COMPOUNDS 



The pyridoxine reciiiirement of young ducklings is similar to that of 

 chicks, approximately 250 7 per 100 g. of ration.^^ 



8. Other Animals 



Fox pups require less than 200 7 per 100 g. of ration.^^ Rainbow trout 

 need 100 to 1000 7 of vitamin Be per 100 g. of diet. 



Ruminants do not require an external source of vitamin Be, for the vita- 

 min is synthesized in adequate amounts in the rumen and reticulum of the 

 sheep and in the rumen of the cow.^^ Milk from a cow fed a vitamin B-com- 

 plex deficient diet has as much pyridoxine as milk from cows fed a normal 

 ration. 



It has been fairly well established that with the B vitamins the smaller 

 species have a higher relative B-vitamin requirement than the larger ones.^'' 

 Figure 4 illustrates this fact with respect to pyridoxine.^^ 



B. OF MAN 

 P. GyOrgy 



As stated in the section deaUng with the effects of vitamin Be deficiency, 

 there cannot be any doubt as to man's need for vitamin Be . The human 

 dietary requirement for vitamin Be has not yet been definitely established. 

 It has been estimated to be in the neighborhood of 1.5 mg. per day for 

 adults,^^ or about 0.03 mg. per kilogram per day.^^ According to recent 

 observations on convulsive seizures in young infants receiving a milk 

 formula low in vitamin Be , the critical level of minimal requirement seems 

 to lie between 0.06 and 0.1 mg. per day for infants up to 4 to 6 months of 

 age — thus about 0.01 to 0.02 mg. per kilogram per day. 



Factors influencing the requirement for pyridoxine in man have not yet 

 been studied. No natural antagonists of pyridoxine are known. It appears 

 from clinical observation that pregnancy and x-ray irradiation might in- 

 crease the need for pyridoxine. More direct or indirect evidence is needed 

 before such a conclusion could be considered as firmly established. 



31 D. M. Hegsted and M. N. Rao, J. Nutrition 30, 367 (1945). 



»2 A. E. Schaefer, C. K. Whitehair, and C. A. Elvehjem, J. Nutrition 34, 131 (1947). 



33 L. W. McElroy and H. Goss, J. Nutrition 20, 541 (1940). 



34 E. Eeerstecher, Jr., Sciejice 111, 300 (1950). 



3* R. J. Williams, R. 1']. Eakin, E. Beerstecher, Jr., and W. Shive, in The Biochem- 

 istry of B Vitamins. Reinhold Publishing Corp., New York, 1950. 



36 R. J. Williams, J. Am. Med. Assoc. 119, 1 (1942). 



3' R. J. Williams, R. E. Eakin, E. Beerstecher, Jr., and W. Shive, in Tlic Biochem- 

 istry of B Vitamins. Reinhold Publishing Corp., New York, 1950. 



