Bacteria in the gut can trigger cancer by breaking down carbohydrate food, a study has found.

In tests on mice predisposed to cancer, microbes metabolising carbohydrates caused gut wall cells to proliferate and generate tumours.

By either treating the mice with antibiotics or feeding them a low carbohydrate diet, scientists were able to reduce the number of tumours in the animals’ small intestines.

The findings, published in the journal Cell, suggest that such simple interventions could ­prevent bowel cancer in at-risk individuals.

Lead researcher Alberto Martin, from the University of Toronto in Canada, said: “By providing a direct link between genetics and gut microbes, our findings suggest that a diet reduced in carbohydrates as well as alterations in the intestinal microbial community could be beneficial to those individuals that are genetically predisposed to colorectal cancer.”

Bowel, or colorectal, cancer is frequently associated with faulty mutant versions of a tumour suppressor gene called APC, and MSH2, a DNA repair gene.

Mice used in the experiments had both genetic variants, ­making them vulnerable to the disease.

Treatment reduced populations of certain gut bacteria that process carbohydrates to produce a fatty acid called butyrate.

Increasing butyrate levels in antibiotic-treated mice boosted cell growth and tumour numbers.