Growth-depressing and Cholesterol-lowering Effects of Quillaja and Tea Saponins in Chicks as Influenced by Diet Composition

Abstract

Certain saponins are known to have both growth-depressing and cholesterol-lowering effects in chicks. Taking into account the proposed mechanism underlying both effects, it seems reasonable to consider that the growth-depressing effect of saponins is associated with the cholesterollowering effect. However, inconsistent results were also reported. In the present experiment, the relationship between growth depression due to saponins and their cholesterol-lowering effect was investigated under the different dietary conditions. Seven-day-old male chicks were fed experimental diets for 10 days. Tea and Quillaja saponins retarded chick growth rate; the former was more toxic than the latter when cholesterol was not included in the diet. However, the addition of cholesterol alone or together with beef tallow alleviated the growth depression due to saponins partly or completely, extent of which depended on the dietary saponin levels. Phytosterols and cholestyramine completely prevented the increase in serum cholesterol concentrations due to dietary cholesterol alone or together with beef tallow or sodium cholate. On the other hand, the hypocholesterolemic effect of the two saponins was only observed when cholesterol and beef tallow were incorporated simultaneously into the diet and, even in this case, the effect of saponin was inferior to that of phytosterols or cholestyramine. Thus, the growth-depressing effect of saponin was not always accompanied by the hypocholesterolemic effect.