FACTORS ALTERING CONCENTRATION OF CAROTENOIDS 493 



in the girls than in the boys. However, just before the start of adoles- 

 cence, there was a decrease in carotene in the case of girls, with the result 

 that a lower average was obtained than in boys of the same age. It was 

 suggested that this variation at puberty is associated with differences in 

 rate of growth in the two sexes at that time. Abels et al. 8i0 reported that 

 both carotene and vitamin A in the plasma are higher in males than in fe- 

 males. 



(e) Seasonal Changes in Plasma Carotene and Vitamin A. A marked 

 seasonal variation in the serum content of carotene and vitamin A occurs 

 in the blood of cattle. Braun 852 reported that these variations coincided 

 with changes in the quantity of carotenoids available in the diet. The 

 age and breed of the cows had only a minor effect. It was found that the 

 vitamin A : carotenoid level in the plasma decreased with increasing caro- 

 tenoid levels in the blood, but tended to reach a constant value when the 

 carotenoid levels were high. The. average maximum level of carotenoids 

 in the Holsteins was 1.35 milligram per cent (1350 microgram per cent) 

 in March when on green pasturage, while the minimum mean value which 

 was noted in October was 0.28 milligram per cent. The maximum levels 

 for vitamin A also approximated 43.5 microgram per cent (145 I.U.) in 

 the March samples, while the minimum average obtained in the Septem- 

 ber and October samples was 10 microgram per cent (35 I.U.). The 

 values for the Holsteins were somewhat lower than those for other breeds 

 during the period when the blood carotene and vitamin A were at a high 

 level. 



Lord 869 reported a similar seasonal variation for Ayrshire cows, with a 

 corresponding difference in the carotene and vitamin A level in the butter. 

 The averages for serum carotene and vitamin A in the summer during 

 pasture feeding were 1350 and 45 microgram per cent (150 I.U.), respec- 

 tively, as compared with values during stall feeding, in the winter, of 230 

 and 9.3 jug. (31 I.U.), respectively. 



Since, in most areas, the intake of green foods does not vary to the same 

 extent in man as it does in cattle, such variations in blood level do not 

 exist ordinarily ; however, it is known that the maintenance of blood caro- 

 tene is dependent upon a continued supply of this carotenoid in the food. 

 On the other hand, Szymanski and Longwell 859 reported a significant sea- 

 sonal variation in plasma carotene levels in children; the average figures 

 (microgram per cent) were as follows: June-November (166 determina- 

 tions) 152; December-May (176 determinations) 132. No seasonal varia- 

 tions in plasma vitamin A were evident. 



869 J. W. Lord, Biochem. J., 39, 372-374 (1945). 



