698 XI. VITAMINS E (tocopherols) 



fecal tocopherol represents an unabsorbed fraction, and how much can be 

 accounted for by reexcretion of absorbed tocopherol through the bile, 

 since it is known that the latter secretion has a vitamin E content similar 

 to that of the plasma.^' 



Bile is a requirement for the absorption of ^^tamin E, just as it is for 

 the carotenoids, vitamin A, vitamin D, vitamin K, and the fats. Thus, 

 Greaves and Schmidt"^ found that vitamin E was not absorbed when fed 

 to choledochocolostomized rats. Moreover, Brinkhous and Warner"^ 

 noted that dogs with bile fistulas Avere incapable of absorbing this vitamin. 

 No information is available as to whether or not the bile acids form co- 

 ordination compounds with vitamin E, or in what manner the}'' mediate 

 their action. 



Tocopherol is absorbed relatively rapidly by the rat. Swick and 

 Baumann''** noted the highest concentration of a-tocopherol in the gut 

 wall (which presumably would coincide Avith the time of maximum ab- 

 sorption) five hours after the ingestion of free a-tocopherol and eight hours 

 after the feeding of a-tocopheryl acetate. In the case of man, Quaife 

 et al}'^ reported that maximum serum levels (which also should coincide 

 roughly Avith the period of maximum absorption) were reached four hours 

 after a 500 mg. dose of a-tocopherol had been given. This value amounted 

 to 1.75 mg./lOO ml. serum. 



The ease of absorption of the tocopherols varies Avith the seA'eral members 

 of the vitamin E group. Thus, in the case of the human subject studied 

 by Quaife et al.,^^ although the maximum serum tocopherol leA^el AA^as 

 reached after about the same interA'al Avhen 7-tocopherol had been fed as 

 after the feeding of a-tocopherol, namely four hours, the peak figure was 

 only 1.35 mg. % in the former case, as compared AAith 1.75 mg. % for the 

 a-tocopherol. Coavs and hens haA^e also been shoAATi to exhibit a preferen- 

 tial absorption of a-tocopherol oA'er the 7- and 5-tocopherols. Thus, 

 Quaife and co-Avorkers^^ reported that a considerable rise in the milk to- 

 copherol IcA'el of coAA^s occurred AA'hen the a-tocopherol AA^as fed. HoAA^ever, 

 in sharp contradistinction to this result, a much less pronounced effect on 

 the milk tocopherol followed the administration of a mixture of tocopherols, 

 98% of AA'hich consisted of 7- and 5-tocopherols. 



In the case of chickens, the most sensiti\'e indices of the efficiency of 

 tocopherol absorption are the tocopherol content in the egg,^^ and the type 



1" J. D. Greaves and C. L. A. Schmidt, Proc. Soc. Exptl. Biol. Med., 37, 40-42 (1937). 



115 K. M. Brinkhous and E. D. Warner, Am. J. Pathol., 17, 81-86 (1941). 



118 R. W. Swick and C. A. Baumann, Arch. Biochem. Biophys., 36, 120-126 (1952). 



