A recent study has found that exposure to a toxin produced by certain bacteria in the bowel may be contributing to the increasing trend of colorectal cancer in young adults around the world. Researchers analyzed DNA from 981 colorectal tumours from patients in 11 countries and discovered that children exposed to colibactin, a toxin secreted by some harmful strains of E coli, before the age of 10 had a higher risk of developing bowel cancer.
The study found that genetic mutations caused by colibactin were more than three times as common in tumours removed from patients under 40 as those over 70. The patterns of mutations suggest that children are exposed to colibactin at an early age, leading to disruptions in DNA and raising the risk of developing bowel cancer before the age of 50.
Global health records show a significant increase in bowel cancer rates among adults under 50 in at least 27 countries, with incidence roughly doubling every decade over the past 20 years. If this trend continues, bowel cancer may become the leading cause of cancer death in this age group by 2030.
While the study does not prove that colibactin drives early-onset bowel cancer, it raises further questions about how these bacteria evolved and gained an advantage in the gut. The researchers suggest that the toxin may help the microbes outcompete their neighbours, leading to a possible link between diet and environmental factors in the development of the gut microbiome.
The study’s findings are consistent with previous research highlighting the importance of diet and lifestyle in preventing bowel cancer. Cancer Research UK states that more than half of bowel cancers are preventable, with dietary factors playing a significant role. The researchers emphasize the need for further research to establish a definitive link between colibactin and early-onset colorectal cancer.
Source: https://www.theguardian.com/society/2025/apr/23/childhood-toxin-exposure-may-be-factor-in-bowel-cancer-rise-in-under-50s