CAROTENOIDS AND VITAMINS A IN THE BLOOD 463 



intake remains constant; this effect occurs concomitantly with a decreased 

 le\'ol of carotene in the butterfat. Similarly, the administration of large 

 doses of vitamin A to hens resulted in a marked depression in the carotene 

 levels of the blood serum, egg yolks, liver and body fat, with a concomitant 

 increase in the vitamin A values in these sites. ^™ For a more complete dis- 

 cussion, see pages 447 to 448. 



(6) Physiologic Factors. Age is an important factor in controlling the 

 level of blood carotene. Minimum levels of blood carotene have been re- 

 ported in the newborn (34 ^lg. % at two days) ; according to Szymanski and 

 Longwell,^*^- there is a gradual increase until a maximum figure of 328 /zg. is 

 obtained at the age of twelve months. Carotene levels during youth have 

 been reported as 126 Mg- % (13-16 years), ^"^ 140 ^g. % (2-12 years), ^'os 116 

 ± 45.7 Mg. % (179 school children),309 and 100 to 168 /xg. % (Michigan 

 children, 6-16 years). ^''^ The figures for blood carotene are apparently 

 lower in the aged than in the case of middle-aged adults. Thus, Rafsky, 

 Newman, and Jolliffe"^ reported mean values of 80 /xg. % (males, 74.7; 

 females, 85) for subjects varying from sixty-nine to eighty-three years. 

 Kirk and Chieffi^^^ observed a progressive decrease in the level of plasma a- 

 and |S-carotenes with increasing age. Gillum, Morgan, and Sailer^'^ also 

 noted a slight decline in the plasma carotene level in older individuals. 



Sex is another factor which appears to have some influence upon the 

 proportion of both plasma carotene and plasma vitamin A. Thus, Kim- 

 ble,^^^ Popper and Steigmann,^^'* and Hoffmann et al.^^^ recorded higher 

 plasma carotene levels in women than in men. A similar sex variation has 

 been noted in infants and young children, ^"^ although the situation becomes 

 reversed at the start of adolescence. Rafsky et al.^^^ reported sex variations 

 in the plasma carotene of aged subjects. On the other hand, Abels et alP^ 

 and Haig and Patek^^^ found that males had a higher plasma carotene value 

 than did females. Although there is thus some disagreement as to the 

 effect of sex on blood carotene, the majority of data indicate that females 



308 C. D. May, K. D. Blackfan, J. F. McCreary, and F. H. Allen, Am. J. Diseases 

 Children, 59, 11G7-1184 (1940). 



'"3 R. F. Kiau.se and H. B. Pierce, /. Nutrition, 33, 633-640 (1947). 



310 A. Robinson, M. Lesher, A. P. Harrison, E. Z. Moyer, M. C. Gresock, and C. 

 Saunders, /. Am. Dietet. Assoc, 2J,, 410-416 (1948). 



3'i H. A. Rafsky, B. Newman, and N. Jolliffe, Gastroenterology, S, 612-615 (1947). 



"2 E. Kirk and M. Chieffi, /. Nutrition, 36, 315-322 (1948). 



3" H. L. Gillum, A. F. Morgan, and F. Sailer, J. Nutrition, 55, 655-670 (1955). 



"4 H. Popper and F. Steigmann, J. Am. Med. Assoc, 123, 1108-1114 (1943). 



315 R. Hoffmann, A. Schneider, and Y. Quamo, J. Invest. Dermatol., 15, 409-419 

 (1950). 



316 C. Haig and A. J. Patek, Jr., J. Clin. Invest., 21, 309-317 (1942). 



