A sharp rise in early-onset colon cancer may be linked to a dangerous strain of E. coli found in ready-to-eat foods like chopped lettuce, according to new research.

Between 2016 and 2023, cases of non-O157 shiga toxin-producing E. coli (STEC) in England rose from 297 to 2,341, affecting over 9,300 people and causing several deaths and serious illnesses.

Researchers found colibactin—a cancer-associated toxin produced by certain E. coli strains—in colon tumors of patients under 40. These cases were 3.3 times more likely to have the toxin than tumors in older patients.

Contaminated lettuce in pre-made sandwiches was linked to an outbreak last year that killed two people. Experts urge caution with raw produce and recommend seeing a doctor for symptoms like changes in bowel habits, fatigue, or unexplained weight loss. Longer-term studies are needed to confirm the toxin’s role in cancer development.