For decades, scientists have been studying the role the human microbiome plays on health. The gastrointestinal tract, or simply the “gut,” is made up of a series of organs essential for breaking down food, absorbing nutrients, and excreting waste. But it also harbors a vibrant, complex community of trillions of bacteria, fungi, and other microbes that together make up the gut microbiome. In addition to controlling digestion, the gut microbiome is in constant close communication with the immune system. In...