The purpose of this study was to determine whether the digestibility of rice protein was responsible for reducing cholesterol levels in mice. Three groups of mice were fed diets with varying protein sources: casein (a milk protein), rice protein extracted by enzymes, or rice protein extracted by chemicals. The digestibilities of both rice protein diets were in fact lower than that of the casein diet. The cholesterol levels of mice in the in both rice protein groups also happened to be lower than those mice in the casein group. As such, there was a significant correlation between the digestibility and cholesterol levels, indicating a link between these two factors. Of both rice protein diets, more fecal bile excretion was noted in rats fed the rice protein extracted by natural enzymes, indicating that cholesterol absorption was more effectively inhibited. This was most likely due to higher fiber content in this rice protein, rather than the one extracted by chemicals.
Reference: Yang L, et al. Rice protein extracted by different methods affects cholesterol metabolism in rats due to its lower digestibility. Int J Mol Sci. 2011; 12: 7594-7608