The gastrointestinal Microbiota in Cancer

The microbiota of the human gastrointestinal tract and in particular the large intestine, comprises a large and diverse range of microorganisms, with over¹⁰12 bacteria per gram of contents (1). It is therefore not surprising that the activities of this microbial population have a significant impact on the health of the host. The microbiota interacts with its host at both the local (intestinal mucosa) level, and systemically, resulting in a broad range of immunological, physiological, and metabolic effects. From the standpoint of the host, these effects have both beneficial and detrimental outcomes for nutrition, infections, xenobiotic metabolism, toxicity of ingested chemicals, and cancer.