Overview

• Dietary proteins from soy, casein, brown rice, yeast, pea, and egg white were detected in feces, showing that even highly digestible sources can reach the colon.
• Brown rice protein accounted for about half of the fecal proteins, while a notable fraction of egg white proteins also escaped digestion.
• Differences tied to the gut microbiota emerged primarily in the large intestine and feces, with small intestine digestion largely unaffected by microbial presence.
• Bioactive components such as the soy Kunitz trypsin inhibitor and egg white proteins lysozyme and avidin persisted to the colon and were accessible to microbes.
• The peer-reviewed mouse study appears in Food & Function with NIH support, and the authors say follow-up work will probe health effects of these source-specific interactions.