Comparative studies on soy protein and rice protein for cholesterol metabolism in rats

The serum level of cholesterol in rats fed a diet containing soy protein isolate was lower than that in rats fed either casein or rice protein at the level of 15% even after one day feeding, although fecal excretion of bile acids of rats fed soy protein isolate was almost equal with that of rats fed rice protein. Similar effect was also observed in the secretion rate of lipoproteins from the liver. Dietary proteins may affect the synthesis of apolipoproteins directly or through the hormonal system.