The effect of dietary casein and soybean protein on plasma lipid levels in cebus monkeys fed cholesterol-free or cholesterol-enriched semipurified diets

Abstract

Two groups of six cebus monkeys were alternately fed semipurified diets containing either casein or soybean protein for periods of 8–10 weeks. The type of protein in the diet had little effect on the plasma cholesterol levels when cholesterol-free diets were fed. However, when 0.2% cholesterol was added to the diets, transferring the monkeys from a soybean protein diet to a casein diet resulted in a significant increase in plasma cholesterol levels (7.97 ± 1.09 versus 9.33 ± 1.31 mmol/L, n = 6, mean ± SD). On the other hand, changing the monkeys from a casein diet to a soybean protein diet significantly lowered the plasma cholesterol levels (9.64 ± 0.58 versus 7.41 ± 1.07 mmol/L, n = 6, mean ± SD). These changes in plasma cholesterol concentrations were attributed to changes in very-low and low-density lipoprotein cholesterol concentrations. The results of his study suggest that the differential cholesterolemic effect of dietary casein and soybean protein in cebus monkeys becomes more pronounced when cholesterol-enriched diets are fed.