Childhood toxin exposure 'may be factor in rise of bowel cancer'

Childhood exposure to a toxin produced by bacteria in the bowel may be contributing to the rise of colorectal cancer in under-50s around the world, researchers say.

- Ian Sample Madeleine Finlay

Countries, including some in Europe and Oceania, have witnessed an increase in young adults with bowel cancer in recent decades. Some of the steepest increases were reported in England, New Zealand, Puerto Rico and Chile.

Doctors have pointed to soaring rates of obesity, widespread junk food and physical inactivity as potential drivers of colorectal cancer, but the new study finds that harmful strains of the common gut microbe E coli may be involved.

Prof Ludmil Alexandrov at the University of California, San Diego, said: "We think what we're seeing is an infection in early life that subsequently increases one's risk for developing colorectal cancer in the future."

In an effort to understand the trend, an international team led by the University of California, San Diego analysed DNA from 981 colorectal tumours from patients in 11 countries in North America, South America, Asia and Europe. The majority of tumours were from older people, but 132 were early-onset bowel cancers.