Humans have 10X more bacteria in their bodies than we do cells. Think about that. And the bacterial colony inside the GI tract can support us, or destroy us. This huge colony of microorganisms is now considered to be the largest organ in the human body. It serves a highly beneficial function, but we're destroying it with modern medicines and diets, especially Antibiotics . Check out this cool slideshow. http://discovermagazine.com/galleries/zen-photo/m/microbiome