The Influence of Roughage on Protein Digestibility

Abstract

Filter paper, China clay, and rice chaff have been fed to rats at different levels with a cooked rice diet. The results indicate that neither varying the total amount of food nor adding large amounts of these bulk materials produces any significant effect upon the degree of digestibility of the food protein. China clay was fed in levels up to 80 per cent of the total intake. It would appear that great bulk in the alimentary canal does not interfere with the action of proteolytic enzymes. Agar agar caused a rapid passage of the food material through the alimentary tract and showed distinctly lowered values for protein digestibility. An experiment with two human subjects in which cabbage fiber was fed with a meat-rice diet showed a slight tendency toward a lowered degree of protein digestibility only when the fiber was ingested in an abnormally large amount. It is suggested that lowered values for nitrogen digestibility on a given diet result only when the food material passes through the alimentary tract with unusual rapidity.