Plasma and lipoprotein cholesterol in weanling and post-weaning rats fed casein and soya protein diets

Plasma and lipoprotein cholesterol levels were measured in groups of Sprague-Dawley weanlings nursed by dams fed either casein (CS) or soya protein (SP). The 6 protein diets were as follows: 8% CS, 8% SP, 8% CS-SP (1:1 mixture), 25% CS, 25% SP and 25% CS:SP (1:1 mixture). A 7th group of dams was fed Purina chow diet. Feeding was from day 15 of pregnancy through 21 days past parturition. Plasma samples taken from other litter sets of young rats fed the above diets from weaning to 6 weeks of age were also analyzed. Plasma total cholesterol was higher at weaning than at 6 weeks of age. The increased level at weaning was due mainly to a rise in LDL-cholesterol, accompanied by a corresponding decrease in HDL-cholesterol. No hypocholesterolemic effect of dietary SP, compared to CS, was evident at this age. However, the effect became manifest at 6 weeks of age (P<0.05), as shown by decreased levels of LDL-cholesterol.