Bacteria in the gut could hold the key to a new way of tackling bowel cancer, research suggests.
Scientists have discovered a powerful link between high fat diets, intestinal bacteria, and the disease.
The study points to bacteria playing a central role in the development and growth of bowel tumours.
Working with mice, the researchers showed that fatty food shifted the composition of gut flora - the diverse population of bacteria that inhabit the digestive tract.
This in turn reduced the level of immune system defences against cancer.
The effect was seen in non-obese mice with a mutant version of a gene called Kras that is known to be associated with human bowel cancer.
Treatment to wipe out the bacteria or mimic the presence of protective "friendly" bugs was found to slow down tumour progression.
A team led by Dr Melek Arkan, from the Technical University Munich in Germany, reported the findings in the journal Nature.
The scientist concluded: "Diet-associated cancer development may be based on marked shifts in bacterial communities rather than on the development of obesity and metabolic disorder.
"Thus, personalised dietary interventions might allow an individual's microbiota (flora) to be modulated to promote health, especially in those who are at a high risk because of genetic susceptibility and a high fat intake."
Another discovery was that bowel cancer could be "transmitted" via bacteria-laden faecal samples.
When the samples from mice with bowel tumours were transferred to other healthy animals with the Kras mutation, this was enough to trigger cancer even in the absence of a high fat diet.
Treating mice with bowel cancer with antibiotics to kill their gut bacteria led to a slowdown in tumour progression.
The same effect followed treatment with butyrate, a fatty acid produced in the gut by the fermenting action of "friendly" bacteria.
Butyrate is a w idely available supplement said to benefit people with inflammatory bowel conditions such as Crohn's disease.