Protein content plays a major role in butyrate production in gut microbiota fermentation

The modern diet delivers nearly equal amounts of carbohydrates and protein compared to ancient high-fiber diets. Meanwhile, plant-based protein foods have become increasingly popular in recent years, and these sources of protein are generally more resistant to digestion than animal protein sources. As a result, a significant amount of protein is expected to reach the colon and be available for fermentation by gut microbiota. While current studies on diet-microbiota interventions have mainly focused on carbohydrate fermentation, limited attention has been given to the role of protein or protein-fiber mixtures as a fermentation substrate in the colon. In this study, we aimed to investigate 1) how changing the ratio of protein to fiber substrates affects the types and quantities of gut microbial metabolites produced; and 2) how the specific fermentation characteristics of different types of fiber might influence the utilization of protein by gut microbes to produce beneficial short chain fatty acids.