VII. EFFECTS OF DEFICIENCY 543 



and (4) rate of nu'tal){)li(' utilization. In such considerations, \i is custc^mary 

 to express vitamin K in terms of rZ-cv-tocophorol, which constitutes about 

 i)0% of the total tocopherol in human tissues and .seems to be al)S()il)ed 

 more efficiently than, or preferentially to, the non-a forms which represent 

 about one-half the usual dietary supply."^ 



o. Dietary Intake 



Chemical and biological analyses indicate that tocopherols are present 

 in essentially every article of diet; yet, the richest sources such as vegetable 

 oils, unmilled cereals, and eggs constitute a much smaller proportion of the 

 usual dietary than animal products, vegetables, and fruits, which represent 

 relatively poor sources of a-tocopherol. It has been estimated that the aver- 

 age American dietary provides approximatel}' 14 to 19 mg. of d-a-tovo- 

 pherol, daily, '^^ and that the better diets probably do not provide more 

 than 25 mg.^*^ Furthermore, the recommended diet of the National Re- 

 search Council (1945) and certain therapeutic diets (low sodium, diabetic) 

 would convey only about one-half this amount."^ The same is true of the 

 aN-erage diet in Holland. ^^^ The estimates do not take into consideration 

 the losses of tocopherol which may occur during storage, commercial hand- 

 ling, and cooking, concerning which very little information is yet available. 



h. Intestinal Absorption and Excretion 



The question of how efficiently the gastrointestinal tract absorbs ingested 

 tocopherol has recei^-ed scant attention. It has been recognized that little 

 or none is excreted in the urine^^^- ^" and that appreciable amounts are 

 lost in the feces. ^^^'^^^ The tocopherol content of bile is of about the same 

 magnitude as that of the blood, and undoubtedly some absorbed tocopherol 

 is re-excreted into the intestinal tract via the biliary tract. i"' >^^ On the 

 basis of bioassay tests, Hickman et al.^^* concluded that in normal human 

 subjects the ratio between ingested and excreted tocopherol is of the order 

 of 4 to 1.2. On the other hand, recent studies of Klatskin and ]Molander,i^^ 

 based on chemical analyses for fecal tocopherol and a larger number of 

 subjects, indicate that normal individuals excrete approximately two-thirds 

 of ingested tocopherol in the feces; they are also of the opinion that there 

 is little or no destruction in the gastrointestinal tract, and concur with 

 others that intestinal .synthesis of tocopherol is ([uite unlikely. On the as- 



1" M. L. Quuife, VV. J. Swanson, M. Y. Dju, and P. L. Harris, Ann. N. Y. Acad. Sci. 



52, .300 (1949). 

 '*» P. L. Harris, M. L. Quaife, and W. J. Swanson, /. Nutrition 40, 367 (1950). 

 1" C. Engel, Ann. N. Y. Acad. Sci. 52, 292 (1949). 

 '" G. Klatskin and D. W. Molander, /. Clin. Invest. 31, 159 (1952). 

 '" G. Klatskin and D. W. Molander, /. Lab. Clin. Med. 39, 802 (1952). 

 '" K. C. D. Hickman, M. W. Kaley, and P. L. Harris, /. Biol. Chem. 152, .321 (1944). 



