290 IV. DIGESTION OF LIPIDS OTHER THAN FATS 



testine in the case of the rat, 231 - 257-262 and the goat, 263,264 as is now believed 

 to be the case, it would be anticipated that any effect of thyroxine or 

 thiouracil on the conversion of the provitamin A to vitamin A would be 

 greatest if these substances were administered by the oral route. How- 

 ever, Chanda and co-workers 251 reported that the digestibility of carotene 

 was altered as readily when thyroid preparations were given by the 

 parenteral route as when they were administered orally. This would 

 indicate that the beneficial effect of thyroid must be exerted on the ab- 

 sorption of carotene rather than on its subsequent metabolism. 



P. The Effect of Substances Fed Concomitantly with /3-Carotene on 

 Its Absorption: The beneficial effects of fats and oils on the absorption 

 of carotene have already been discussed. Other substances, when present 

 in the gut simultaneously, may likewise help or hinder the absorption of 

 the provitamin A. 



(a') The Effect of Mineral Oil. — The presence of difficultly absorbed 

 hydrocarbons such as mineral oil will have a deleterious effect on carotene 

 utilization. Rowntree 265 was the first to report that the minimum quanti- 

 ties of vitamin A required for the growth of rats were inadequate when 

 mineral oil was present in the diet. Dutcher and associates 266 found that 

 carotene absorption was depressed by this hydrocarbon to a far greater 

 extent than was that of vitamin A. The deleterious effect of mineral oil 

 on carotene absorption also applies to man. Thus, it was reported that 

 plasma carotene values and the vitamin A in the liver were increased to 

 a lesser degree after the ingestion of carotene in the presence of mineral 

 oil than when the latter substance was absent. 267 - 268 These results have 

 been confirmed by a number of workers. 269-279 



257 F. H. Mattson, J. W. Mehl, and H. J. Deuel, Jr., Arch. Biochem., 15, 65-73 (1947). 



258 S. Y. Thompson, J. Ganguly, and S. K. Kon, Brit. J. Nutrition, 1, v (1947). 



269 S. Y. Thompson, J. Ganguly, and S. K. Kon, Brit. J. Nutrition, 3, 50-78 (1949). 



260 J. Glover, T. W. Goodwin, and R. A. Morton, Biochem. J., 41, xiv (1947). 



261 J. Glover, T. W. Goodwin, and R. A. Morton, Biochem. J., 48, 512-518 (1948). 



262 A. B. McCoord and S. W. Clausen, Abst., 114th Meeting, Am. Chan. Soc, Div. 

 Biol. Chem., Washington, Aug. 30, 1946, 16 C. 



263 T. W. Goodwin, A. D. Dewar, and R. A. Gregory, Biochem. J., 40, lx-lxi (1946). 



264 T. W. Goodwin and R. A. Gregory, Biochem. J., 48, 505-512 (1948). 

 266 J. I. Rowntree. J. Nutrition, 8, 345-351 (1931). 



266 R. A. Dutcher, P. L. Harris, E. R. Hartzler, and N. B. Guerrant, J. Nutrition, 8. 

 269-283 (1934). 



267 A. C. Curtis and E. M. Kline, Arch. Internal Med., 63, 54-63 (1939). 



268 B. Alexander, E. Lorenzen, R. Hoffmann, and A. Garfinkel, Proc. Soc. Exptl. Biol. 

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



269 O. Andersen, Klin. Wochschr., IS, 499-502 (1939). 



270 A. C. Curtis and R. S. Ballmer, /. Am. Med. Assoc, 118, 1785-1788 (1939). 



271 D. L. Collison, E. M. Hume, I. Smedley-MacLean, and H. H. Smith, Biochem. J., 

 M, 634-647 (1929). 



