A new study suggests that childhood exposure to a bacterial toxin called colibactin, produced by a strain of E. coli, may be contributing to the rise of colorectal cancer in young people. The research indicates that these mutations can leave a genetic fingerprint on colon cells, increasing cancer risk before age 50. The study analyzed samples from 981 patients across 11 countries and found that colibactin-linked mutations were significantly more common in younger cancer patients. Experts call for further research to confirm these findings and understand the implications for gut health.