Simple version: if you don’t feed your gut microbes they’ll start chewing on you to survive. Eat your soluble fiber and resistant starches.

Yes it makes you fart for the first week. It goes away as your microbes adapt to a preferred food source.

Source of info: I used to have leaky gut syndrome.

Main symptoms: anxiety, depression, constipation alternating with diarrhea.

Fiber supplements currently in use: unmodified potato starch (cheap), inulin fiber derived from chicory (flavourless, non thickening, disappears into my morning tea without a trace) and xylitol sweetener which gut microbes gobble up like soluble fiber (yes xylitol is toxic to dogs as someone always points out whenever that word comes up).