Plant proteins are less digestible than animal proteins due to structural features including β-sheet conformation, disulfide cross-linking, and entrapment in plant cell walls, resulting in greater delivery of undigested protein to the colon where it serves as a substrate for microbial fermentation.

Plant proteins have tough structures that stomach and intestinal enzymes cannot fully break down, so large pieces reach the colon. There, gut bacteria use these protein pieces as food and break them down into short-chain fatty acids and other compounds. These compounds change the gut environment, feed the cells lining the colon, and reduce harmful bacteria. Some leftover pieces also turn into other molecules that affect blood pressure and heart health.