28S IV. DIGESTION OF LIPIDS OTHER THAN FATS 



the blood stream in man in solution, in the form of fine fat particles which 

 are absorbed as the triglyceride. 



d'. The Effect of Emulsifying Agents on the Absorption of /3-Carotene: 

 The beneficial effect of fat on carotene absorption must lie in its solvent 

 action. On the other hand, the favorable action of bile salts must be 

 related to their action in bringing about an emulsification of the fat and 

 thus assisting in the digestion and absorption of this foodstuff. 



Emulsifying agents other than bile salts are now known to aid in the 

 absorption of carotene. This fact was first observed by Adlersberg and 

 Sobotka 239 in man. It was later shown by Adlersberg and associates 240 

 that butter which contained phospholipid was a better vehicle in bringing 

 about the absorption of carotene than was cottonseed oil, from which 

 phospholipid is largely absent. However, when lecithin was added to the 

 cottonseed oil, the absorption of carotene from this modified solvent 

 was at a higher level than was the case when butter was the solvent. 

 Esh and Sutton 241 also reported that lecithin improves the absorption of 

 both carotene and vitamin A in the rat. However, it was shown that 

 choline failed to exert a beneficial effect on absorption. Slanetz and 

 Scharf 242 ' 243 obtained similar results with lecithin. 



The enhanced provitamin A activity of carotene, when present in 

 margarine, 244 has been attributed to the improved absorption caused by 

 such emulsifying agents as lecithin and mono- and diglycerides; these 

 increase the dispersibility of margarine in water, at body temperature, 

 and thus increase the physiological availability of the provitamin, through 

 an augmented absorption. Lecithin has likewise been shown to facilitate 

 the absorption of high melting fats and vitamin A (see pages 185 and 317). 



Tween 40 (polyoxyethylene sorbitan monopalmitate) has been widely 

 used for producing water-soluble solutions of carotene for oral and par- 

 enteral injection. Thompson et al. 231 reported that an aqueous colloidal 

 solution of carotene was approximately as efficiently utilized as when the 

 provitamin A was given in an oil solution. Burns, Hauge, and Quacken- 

 bush 245 reported that the growth of rats fed carotene emulsified in a water 



239 D. Adlersberg and H. Sobotka, /. Nutrition, 25, 255-263 (1943). 



240 D. Adlersberg, S. Kann, A. P. Maurer, K. Newerly, W. Winternitz, and H. Sobotka, 

 Am. J. Digestive Diseases, 16, 333-337 (1949). 



241 G. C. Esh and T. S. Sutton, ./. Nutrition, 36, 391-404 (1948). 



242 C. A. Slanetz and A. Scharf, Proc. Soc. Exptl. Biol. Med., 53, 17-19 (1943). 



243 A. Scharf and C. A. Slanetz, Proc. Soc. Exptl. Biol. Med., 57, 159-161 (1944). 



244 H. J. Deuel, Jr., S. M. Greenberg, E. E. Savage, and D. Melnick, J. Nutrition, 43, 

 371-388(1951). 



246 M. J. Burns, S. M. Hauge, and F. W. Quackenbush, Arch. Biochem., SO, 341-346 

 (1951). 



