Bowel cancer is expected to be the leading cause of cancer death in people under 50 by 2030. One new focus of research is colibactin, a toxin produced by certain strains of E. coli bacteria in the gut. Colibactin damages DNA in the cells lining the bowel, creating mutations that can eventually lead to cancer. A study analyzing 981 bowel cancer samples from 11 countries found that these colibactin-linked mutations were more than three times as common in patients diagnosed before age 40 compared to those diagnosed over 70. Researchers believe early life exposure, possibly before the age of 10, allows DNA damage to accumulate over decades, speeding up the timeline for cancer development. Although rising obesity, poor diets, and inactivity are still important factors, colibactin points to a hidden environmental risk that starts much earlier than previously thought. While the study does not prove colibactin is the direct cause, it adds a major clue to understanding why early-onset bowel cancer is increasing. Scientists are now investigating how children are exposed to colibactin-producing bacteria and whether interventions like probiotics could reduce risk. With cases continuing to climb, finding clear answers and prevention strategies has become increasingly urgent. Building a healthy gut microbiome early through a high-fiber diet, limited processed foods, and careful antibiotic use may help lower the risk of early-onset bowel cancer.