The Garden in Your Gut By  Amanda Kolson Hurley Probiotics and fermented foods are all the rage for digestive health, but do they really work? Here’s what scientists are discovering about the trillions of microbes that live in our bodies and how this complex ecosystem—which some call the “second brain”—influences not just our digestion but our overall well-being. In the first scene of his tragedy Coriolanus, Shakespeare weaves a vivid metaphor of the Roman republic as a human body, an organism that can’t function unless all its constituent parts work together. The Roman Senate rules this body, but not as its head—as its belly.   The belly, explains a senator in the play to a rebellious commoner, delivers its sustenance to all your limbs and organs, “through the rivers of your blood, / Even to the court, the heart, to the seat o’ the brain.” In the same manner, he says, the Senate “digest[s] things rightly / Touching the weal o’ the common,” then disburse...