New research suggests that Helicobacter pylori, a bacterium carried in the stomachs of around 40 per cent of people, could be linked to as many as one in five cases of bowel cancer, offering a possible explanation for rising rates of the disease among younger adults. Scientists say people exposed to the bacteria, often through contaminated food such as unwashed lettuce, leeks or spinach, face a significantly higher risk of developing colorectal cancer, raising the prospect that antibiotics could eventually be used to help prevent the disease in high-risk groups.

Researchers from the University of Hong Kong and the University of California analysed data from 43 studies covering more than 48.7 million people, finding that those exposed to H. pylori had a 59 per cent higher risk of colorectal cancer. Across all studies, they estimated 22 per cent of cases could be linked to the bacterium, though this fell to around 12 per cent when only the strongest studies were considered, with the association strongest in East Asia. The bug, usually acquired in childhood via poor sanitation or contaminated water, can be detected with breath or stool tests and cleared with a week-long antibiotic course; long-term studies found eradicating it cut bowel cancer risk by 10 per cent, though researchers stressed the findings show a link rather than proven causation.