Cholesterol synthesis and absorption by 2H2O and 18O-cholesterol and hypocholesterolemic effect of soy protein

The kinetic behavior of orally ingested 18O-cholesterol was compared with that of orally ingested 13[C.sub.5]-cholesterol in two normocholesterolemic men and the hypocholesterolemic effect of soy protein was demonstrated in 12 hypercholesterolemic men. Our results indicated no difference in the metabolism of orally ingested 18O- and 13[C.sub.5]-cholesterol. The use of 18O-cholesterol and 13[C.sub.5]-cholesterol also allowed simultaneous estimation of fractional rates of cholesterol synthesis using the 2[H.sub.2]O method, which were calculated to be 5.76 and 8.17%/d for the two normocholesterolemic subjects. The percent reduction in plasma cholesterol levels was found to be greater when the hypercholesterolemic men were placed on a soy protein diet than on an animal protein diet. INDEXING KEY WORDS: cholesterol; synthesis; absorption; human; stable isotopes; hypocholesterolemia; soy protein