“…Prebiotics are indigestible food ingredients that improve the gut microbiota structure by providing carbon sources, making metabolic substrates available for the gut microbiota to utilize, and adjusting the gut microenvironment, such as in terms of pH value, gastrointestinal absorption, and enzyme hydrolysis ( 173 , 174 ). Fructo-oligosaccharide (FOS) is a well-studied effective prebiotic consisting of one glucose and one fructose, and it has shown multiple beneficial effects in several animal models including the following: (a) resisting bacterial infection such as that of enterotoxigenic E. coli ( 176 ), (b) promoting the colonization of probiotics like Bifidobacterium and Lactobacillus ( 177 – 180 ), (c) increasing the production of SCFAs by the use of these probiotics ( 180 ), and (d) downregulating the pro-inflammatory cytokine expression and protecting the mucosal barrier ( 181 ). Besides FOS, inulin, galacto-oligosaccharides, and some foods containing indigestible β-glucans such as termites, a kind of Chinese traditional medicine, also have a similar effect ( 174 ).…”