The effect of semipurified diets containing two levels (20% and 40%) of either casein or soybean protein isolate and concentrate on plasma lipids in hamsters

Abstract

Six groups of 10 F 1B hamsters were fed cholesterol-enriched (0.1%) semipurified diets containing two levels (20% and 40%) of casein, soybean protein isolate, and soybean protein concentrate. The hamsters fed the 20% casein diet had higher plasma cholesterol levels (7.05±1.38 mmol/L, Mean± SD, n=10) than those fed the 20% soybean protein isolate (5.73±0.64 mmol/L) or the 20% soybean protein concentrate (5.39±0.63 mmol/L). Increasing the proportion of dietary casein, soybean protein isolate, and soybean protein concentrate from 20% to 40% increase dthe plasma cholesterol concentrations, irrespective of the type of protein in the diet; however, the hamsters fed the 40% casein diets had higher plasma cholesterol concentrations (10.47±4.55 mmol/L) than those fed the 40% soybean protein isolate (7.12±0.88 mmol/L) and 40% soybean protein concentrate (6.34±0.74 mmol/L). Differences in plasma cholesterol levels between the various groups were reflected in differences in very low density and low density lipoprotein (VLDL+LDL) cholesterol levels, and there were no significant differences between the high density lipoprotein (HDL) cholesterol concentrations. Thus, the results of these studies (a) confirm the differential cholesterolemic effect of dietary casein and soybean protein in the hamster and show in addition (b) that increasing the proportion of protein in the diet increased the plasma cholesterol levels, irrespective of the type of protein.