Cancer is a complex disease that is the world's second biggest cause of mortality. Numerous studies in recent years have underlined the dual significance of the gut microbiota in sustaining the health of the host. The term "gut microbiota" refers to the diverse population of commensal microorganisms, mainly bacteria but also fungi, archaea, and viruses that populate the intestinal tract, particularly the large intestine, and it can be thought of as one factor to which we are constantly exposed, at high doses, throughout our lives. The gastro-intestinal resident bacteria and the human body interact at a sophisticated level in the gut. Gut bacteria can produce a variety of metabolites and bioproducts that help to maintain homeostasis in both the host and the gut.