Dietary Fibers and Foundation Guild for a Healthy Gut Microbiota

Short chain fatty acids (SCFAs) from bacterial fermentation of dietary fibers play essential roles in human nutrition, immunity and metabolism. Our ancestors had much higher intake of dietary fibers than us today. Reduced intake of dietary fibers and diminished diversity of SCFA-producing bacteria may underlie many chronic diseases such as type 2 diabetes and cancer. In patients with type 2 diabetes, increased intake of diverse dietary fibers can selectively promote a group of acetic and butyric acid producers, that can increase insulin secretion by promoting more GLP-1 production in the gut; more importantly, they can acidify the gut environment, produce antimicrobials and occupy available niches to inhibit pathogenic and detrimental bacteria, which may promote inflammation and suppress GLP-1 production. Thus, in addition to providing SCFAs to directly benefit the hosts, this group of SCFA producers plays important ecological functions in the gut microbiota. Akin to tall trees in a closed forest, they work as the “foundation guild” for structuring the healthy gut microbiota. To help patients regain a healthy gut microbiota, this foundation guild must be re-seeded and re-established first.