886 XIV. NI'TRITIONAL VALUE OF FATS 



in the diet. On the other hand, Russell and co-workers--^ reported that 

 the utilization of ^'itamin A in the chicken was not related to the presence 

 of fat in the diet, althoup'h the absorption of carotene by fowl was improved 

 by fat. The retention of vitamin A in the liver was greater in hens which 

 had received a ration with a normal fat content. 



The presence of fat may also influence the relative effectiveness of the 

 various forms of vitamin A. In general, the natural ester of vitamin A 

 is less efficiently absorbed from oil solution than is either the acetate or the 

 free alcohol. In some cases, the acetate ester, also, is poorlj- absorbed. ^•^-'- 

 For a further discussion of the effect of fats on the absorption of vitamin A, 

 see Chapter IX of this volume. 



A number of different investigators ha\'e demonstrated that the utiliza- 

 tion of the provitamin A, ;8-carotene, by the rat depends upon the solvent 

 in which it is fed.--''--'"^-'' Thus Fraps and Meinke,-'^" using a liver 

 storage test as a criterion, reported that carotene was less readily utilized 

 when present in vegetables than when fed as a component of cottonseed 

 oil. Ivreula and Virtanen--^ observed that, in human subjects, the ab- 

 sorption of carotene from carrots was less efficient than when it was fed 

 dissolved in l)utterfat. It has already been reported that Russell and 

 co-workers--^ noted that /3-carotene is efficiently utilized by the chick 

 only if fat is present. According to Burns et al.,^-'' both carotene and 

 vitamin A are more effective in the rat when fed with the diet containing 

 5% of lard than when given with a fat-free diet which was supplemented 

 with 0.1 g. of corn oil daily. Deuel and collaborators^^^ found that caro- 

 tene was more efficiently utilized when it was incorporated in margarine 

 than when fed with cottonseed oil. These workers suggest that the 

 greater physiologic availability of carotene is potentiated by the emulsify- 

 ing agents present in the margarine. 



==• W. C. Russell, M. W. Tavlor, H. A. Walker, and L. J. Polskiii, .7. Xiitrition, 24, 190- 

 211 (1942). 



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



"3 E. J. Lease, J. G. Lease, H. Stcenbock, and C. A. Baumann, J. Nutrition, 17, 91-102 

 (1939). 



22* W. C. Sherman, J. Nutrition, 22, 153-165 (1941). 



"6 G. S. Fraps and W. W. Meinke, Food Research, 10, 187-196 (1945). 



"6M. Kreula and A. I. Virtanen, Upsala Ldkareforen. Fork., 45, 355-362 (1939); 

 Chem. Abst. 34, 5897 (1940); cited by D. Melnick and B. L. Oser, Vitamins and Hor- 

 mones, 5, 39-92 (1947), 59. 



2" M. J. Burns, S. M. Hauge, and F. W. Quackenbush, Arch. Biochon., 30, 341-346 

 (1951). 



228 H. J. Deuel, Jr., S. IVI. Greenberg, E. E. Savage, and D. Melnick, J. Nutrition, 43, 

 371-387(1951). 



