Dietary glycine and cholesterol metabolism in rats

Generally, diets containing casein induce higher concentrations of serum cholesterol in rats than diets containing soybean protein. It has been suggested that at least part of this effect is due to the relatively low level of glycine in casein, when compared to soybean protein. We have tested this suggestion by adding glycine to a semipurified casein diet, so that the level of glycine was similar to that in a diet containing soy protein. The addition of glycine did not affect the casein-induced concentrations of cholesterol in serum and liver of rats. We conclude that the low proportion of glycine in casein does not play a role in casein-induced hypercholesterolemia.