434 IX. CAROTENOIDS AND VITAMINS A 



fication and hydrolysis. However, Gray et al.^^ were not able to demon- 

 strate any such phenomenon in the rat. 



b. Factors Altering the Absorption of Vitamins A. Many of the condi- 

 tions which affect the absorption of the carotenoids are likewise operative 

 in the case of the vitamins A. However, the factors which tend to have a 

 deleterious effect upon absorption are usually quantitatively less active in 

 relation to vitamin A than in the case of the carotenoids. 



The rate of absorption of vitamin A is influenced by the age of the person 

 receiving the vitamin. Thus, Sobel et al. ^^^ observed a markedly diminished 

 rate of utilization in the newborn baby as compared with that of children 

 over one year of age and of adults. Young infants were found to exhibit 

 a low vitamin A tolerance, as contrasted with that of older children.^"* 

 On the other hand, vitamin A was absorbed at a diminished rate in the aged 

 (69 to 89 years). 1°^ 



The rate of absorption of vitamin A was found by Reifman and co- 

 workers^°^ to be a function of the concentration fed. Thus, the amount of 

 vitamin A absorbed, expressed in International Units per 100 sq. cm. of 

 body surface per hour increased progressively from between 4.2 and 6.5, 

 when the dosage was 100 I.U. per 100 sq. cm., to 10,140 at a maximum 

 dosage of 1,000,000 I.U. On the other hand, bile plays a minor role in the 

 absorption of vitamin A. According to Schmidt and Schmidt,'"'^ and Irvin 

 and co-workers,-^ vitamin A can still be efficiently absorbed by choledo- 

 chocolostomized vitamin A-deficient rats, in contrast to the failure of 0- 

 carotene to be utilized under similar conditions. Fat, hkewise, is less 

 essential as a solvent for vitamin A than for carotene, not only in rats,^***'^"^ 

 but also in the fowP"^ and in man.^'- Mineral oil, also, has a less deleterious 

 effect upon the absorption of vitamin A than it has upon that of carotene. 

 In fact, some workers^"^"^^^ failed to demonstrate that mineral oil ex- 



102 A. E. Sobel, L. Besman, and B. Kramer, Atn. J. Diseases Children, 77, 576-591 

 (1949). 



los A. E. Sobel, S. P. Gottfried, B. Kramer, and L. Besman, Abstracts, 110th Meeting, 

 Am. Chem. Soc., Div. Biol. Chem., Chicago, Sept. 11, 1946, 28 B-29 B. 



'0^ H. A. Rafsky and B. Newman, Gastroenterology, 10, 1001-1006 (1948). 



105 A. G. Reifman, L. F. Hallman, and H. J. Deuel, Jr., J. Nutrition, 26, .33-42 (1943). 



los W. Schmidt and C. L. A. Schmidt, Univ. Calif. {Berkeley) Pub. Physiol, 7, 211-221 

 (1930). 



1" N. K. De, Indian J. Med. Research, 2.'+, 751-766 (1937). 



108 W. C. Russell, M. W. Taylor, H. A. Walker, and L. J. Polskin, /. Nutrition, 2J^, 

 199-211 (1942). 



103 E. Moness and W. G. Christiansen, /. Am. Pharm. Assoc., 18, 997-998 (1929). 



110 A. C. Curtis and P. B. Horton, Am. J. Med. Sci., 200, 102-107 (1940). 



111 B. Ale.xander, E. Lorenzen, R. Hoffman, and A. Garfinkel, Proc. Soc. Exptl. Biol. 

 Med., 65, 275-278 (1947). 



