DIGESTION, ETC. OF STEROLS IN THE G.I. TRACT 271 



was markedly decreased. In a later paper of Peterson, Nichols, and 

 Shneour, 133 it was demonstrated that the inclusion of soy sterols in a high 

 (1%) cholesterol diet, fed to chickens over a period of twenty-eight weeks, 

 not only prevented the usual hypercholesterolemia, but also decreased 

 the cholesterol deposition in the liver and the incidence of atherosclerosis. 

 In a still later study of the Peterson group, 76 it was found that dietary soy 

 sterols were able to prevent a progressive rise of plasma cholesterol and 

 the deposition of cholesterol in the liver in chicks fed a diet containing 

 1% of cholesterol with 4% cottonseed oil, and that, furthermore, the addi- 

 tion of mixed sitosterols, /3-sitosterol, stigmasterol, or ergosterol to the 

 diet resulted in a similar inhibition. Moreover, when cholesterol was 

 fed at a constant level and the soy sterols were introduced into the diet 

 at varying levels, the optimum effect in depressing both plasma and liver 

 cholesterol levels was obtained when the ratio of soy sterols to cholesterol 

 was 2:1 or 3:1. Siperstein and co-workers 134 reported that cholestanol 

 likewise prevents the increase of plasma cholesterol in chicks fed a high 

 cholesterol diet. 



Esterification of the soy sterols with capric acid destroyed their ability 

 to prevent the increase in plasma and liver cholesterol caused by feeding 

 cholesterol. Moreover, cholesteryl caprate was ineffective in producing 

 the effects caused by the unesterified cholesterol. It was postulated 

 that the inhibitory effect of soy sterols on cholesterol absorption may 

 therefore be caused by an inhibition of an enzyme system concerned in 

 cholesterol absorption which may involve the esterification of cholesterol. 



(4) Changes in Sterols in the Gastrointestinal Tract 



Although a considerable amount of ingested cholesterol may be ex- 

 creted unchanged in the feces, 103 some of the sterol undergoes a trans- 

 formation in the gastrointestinal tract. Popjak and Beeckmans, 135 by 

 the use of tracers, demonstrated that cholesterol is synthesized in the in- 

 testine. This sterol may be dehydrogenated in the intestine of the guinea 

 pig to yield 7-dehydrocholesterol, 136 or it may be reduced to cholestanol, 

 which is excreted in the feces. 137 Schonheimer and co-workers 126,138 



133 D. W. Peterson, C. W. Nichols, Jr., and E. A. Shneour, J. Nutrition, 47, 57-65 

 (1952). 



134 M. D. Siperstein, C. W. Nichols, Jr., and I. L. Chaikoff, Circulation, 7, 37-11 (1953). 

 136 G. Popjak and M. L. Beeckmans, Biochem. J., 47, 233-238 (1950). 



136 M. Glover, J. Glover, and R. A. Morton, Biochem. J., 51, 1-9 (1952). 



137 A. Windaus and C. Uibrig, Ber., 48, 857-863 (1915). 



138 R. Schonheimer and L. Hrdina, Z. physiot. Chcm., 212, 161-172 (1932). 



