Insights Into the Relationship Between Gut Microbiota and Colorectal Cancer

Purpose of review: There is growing evidence to suggest that gut microbiota plays an important role in colorectal carcinogenesis. Western diet is associated with gut microbial dysbiosis, which leads to inflammation, oxidative stress, and genotoxic effects, all common risk factors for colorectal cancer. Recent findings: Fusobacterium nucleatum, Helicobacter pylori, Bacteroides fragilis, Escherichia coli, and Streptococcus bovis are the main bacterial species associated with colorectal carcinogenesis. Gut microbiota transforms both diet- (meat, processed meat products, fat) and host (bile acids)-derived precursors into carcinogens and further interferes with anti-cancer drug metabolism, chemotherapy efficacy, and drug-induced toxicity. Nutritional interventions, as well as the administration of beneficial bacteria (probiotics), dietary fiber (including prebiotics) supplements, and synbiotics (probiotic + prebiotic), may reduce the risk of colorectal cancer and side effects of anti-cancer therapy. Summary: Current evidence suggests gut microbiota may predispose or protect against colorectal cancer. Restoring gut microbial dysbiosis is an emerging nutritional and clinical target in oncology.