DIGESTION, ABSORPTION, AND DIGESTIBILITY 435 



erted any harmful efTcct whatsoever upon tlie utihzation of vitamm A. 

 Others^ '"-""^ reported some decrease in absorption of vitamin A when this 

 dietary adjunct was consumed, although it was quantitatively of a lower 

 order than that exerted upon /3-carotene. 



One interesting factor which may influence the speed of absorption of 

 vitamin A is its form of administration, i.e., whether it is given as the ester 

 or as the free alcohol. This factor cannot apply to the utilization of caro- 

 tene and of other carotenoids, although it might also be operative in the 

 case of the carotenols. If one accepts the hypothesis that hydrolysis of the 

 vitamin A esters is a prerequisite to absorption, then any conditions which 

 retard or inhibit hydrolysis will likewise decrease the rate of absorption of 

 this vitamin. Thus, Week and Sevigne^'^ noted that the vitamin A storage 

 in the liver of rats following given doses of vitamin A in the form of the free 

 alcohol, the acetate, and the natural ester, was fairly uniform when corn oil 

 or castor oil (which is completely utilized by the rat) was used as the 

 diluent; the alcohol and acetate were stored to a slightly greater degree 

 than the natural ester. However, when the several forms of vitamin A 

 were dissolved in a poorly utilized vehicle such as jojoba oil, the proportion 

 of vitamin A deposited was one-third less when it was fed as the natural 

 ester than when it was given as the free alcohol or acetate. The variation 

 in vitamin A storage, as influenced by the form in which it was given and the 

 vehicle in which it was dissolved, was even more strikingly illustrated in the 

 case of the chicken.^" Man exhibits a similar pattern for utilization of the 

 several forms^^^; thus, after 134,000 iig. of vitamin A had ])een given in 50 

 g. of margarine, the best absorption, as determined ])y the vitamin A toler- 

 ance test, was observed in the case of the free alcohol. This was followed 

 by the acetate, and the poorest showing was noted in the case of the natural 

 ester. Alarch, English, and Biely"^ confirmed the fact that vitamin A 

 alcohol and acetate are better utiUzed than the natural ester when given 

 in cottonseed oil. This difTerence was also shown by the variation in the 

 amount of vitamin A present in the intestinal wall when the several forms 

 of vitamin A were employed. These workers attribute the poorer effect 



112 O. Andersen, Klin. Wochschr., 18, 499-502 (1939). 

 1" T. K. With, Nord. Med., 3, 2468-2470 (1939). 



11* O. Andersen, Acta Paediat., 24, 422-427 (1939). 



115 M. C. Smith and H. S. Spector, Univ. Arizona, Coll. Agr., Ariz. Agr. Expt. Sta., 

 Tech. Bull. No. 84, 373-395 (1940). 



'16 E. F. Week and F. J. Sevigne, /. Nutrition, 39, 251-257 (1949). 

 "^ E. F. Week and F. J. Sevigne, /. Nutrition, 39, 233-250 (1949). 

 118 E. F. Week and F. J. Sevigne, J. Nutrition, 40, 5G3-576 (1950). 



113 B. E. March, E. Enghsh, and J. Biely, Arch. Biochem. Biophys., 36, 259-268 

 (1952). 



