436 IX. CAROTENOIDS AND VITAMINS A 



of the palmitate, as compared to the free alcohol and acetate, to mterfer- 

 ence by the oil with the absorption of the natural ester through the intes- 

 tinal wall, rather than to differences in stability of vitamin A. However, 

 when vitamin A was administered in an aqueous carrier, the reverse situa- 

 tion was obtained, namely the natural ester and the acetate were better 

 utilized than the free vitamin A alcohol. ^^^ 



Emulsifying agents such as lecithin enhance the absorption of vitamin A, 

 not only in the case of rats,^-° but also in the case of cattle ;^^^ lecithin also 

 improves the absorption of vitamin A by human subjects suffering from 

 sprue, but not in patients with liver disease. ^'^ It has likewise been 

 reported by a number of workers,i''2'^°*'i-*"^25 qj^ ^]^g basis of higher blood 

 levels and greater storage of vitamin A in rats, guinea pigs, and children, 

 that aqueous solutions of vitamin A are more effective than are oil solutions 

 of the vitamin. The variations are apparently not related to the form of 

 vitamin A administered, as the improved vitamin utilization when aqueous 

 suspensions were used was equally striking irrespective of whether the 

 free alcohol or the palmitate was employed. ^^® When PSM (Tween 80, 

 polyoxyethylene sorbitan monooleate) was employed as the dispersing 

 agent, Krantz^^'' observed maximum blood values, in normal and in diseased 

 patients, 400 to 500% greater than in the tests in which the vitamin A was 

 administered in oil solution. In 1952, SobeP^^ completed a comprehensive 

 review of vitamin A absorption. 



The thyroid gland also exerts an effect upon vitamin A utilization. 

 Conversely, vitamin A, when given in large doses, may exhibit an anti- 

 thyroid action. ^-^ The storage of vitamin A was found to be highest in 

 thyroidectomized rats, intermediate in those treated with thyroxine, and 

 least in normal control animals. ^^'^ The unexpected result in the normal 



120 G. C. Esh and T. S. Sutton, /. Nutrition, 36, 391-404 (1948). 

 12' G. C. Esh, T. S. Sutton, J. W. Hibbs, and W. E. Krauss, /. Dairy Sci., 31, 461-478 

 (1948). 



122 D. Adlersberg, S. Kann, A. P. Maurer, K. Newerly, W. Winternitz, and H. 

 Sobotka, Gastroenterology, 10, 822-830 (1948). 



123 J. M. Lewis, O. Bodansky, J. Birmingham, and S. Q. Cohlan, /. Pediat., 31, 496- 

 508 (1947). 



124 B. Kramer, A. E. Sobel, and S. P. Gottfried, Am. J. Diseases, Children, 73, 543- 

 553 (1947). 



126 A. E. Sobel, M. Sherman, J. Lichtblau, S. Snow, and B. Kramer, /. Nutrition, 36, 

 225-238 (1948). 



126 B. M. Kagan, D. A. Jordan, and D. S. Gerald, /. Nutrition, AO, 275-279 (1950). 



12^ J. C. Krantz, Unpublished observations; cited in Nutrition Revs., 7, 205-207 

 (1949). 



128 H. E. Sobel, Vitamins and Hormones, 10, 47-67 (1952). 



129 D. P. Sadhu and S. Brody, Am. J. Physiol, 149, 400-403 (1947). 



130 C. B. Heimer, H. L. Maslow, and A. E. Sobel, J. Nutrition, 38, 345-352 (1949). 



