Gut microbiota and diet in colorectal cancer: Converging determinants of carcinogenesis

Diet and the gut microbiome are major, interdependent determinants of colorectal cancer (CRC) risk. This review discusses current evidence on how dietary patterns reshape microbial ecology, modulate microbial virulence, and alter host metabolic, inflammatory, and oncogenic pathways to influence colorectal carcinogenesis. We highlight key CRC-associated microbes, including pks⁺ Escherichia coli, Fusobacterium nucleatum, enterotoxigenic Bacteroides fragilis, and Streptococcus gallolyticus, and discuss how diet governs their abundance, toxin production, and oncogenic potential. Mechanistic investigations into diet-microbe interactions reveal how pro-inflammatory, low-fiber Western-style diets foster mucosal inflammation, generation of reactive oxygen and nitrogen species, and genotoxic microbial niches, whereas fiber- and polyphenol-rich diets support protective commensals and production of anti-inflammatory metabolites. We also outline major challenges, including interindividual microbiome variability and limited translational models, and propose future directions for integrating dietary, microbial, and host-targeted strategies for CRC prevention and therapy.