“…Gut microbes are involved in regulating a variety of host metabolic responses; producing metabolites that are critical to gut health, such as short-chain fatty acids; and metabolizing bile acids, steroids, bile acids, choline, and other molecules [ 104 , 162 ]. In fact, some complex carbohydrates, such as dietary fiber, are digested by gut microbes and fermented at the proximal end of the colon to produce short-chain fatty acids, such as butyric acid, acetic acid, and propionic acid, which are known to have important neural activity [ 51 , 163 ].…”