High levels of iron may be one reason why eating red meat raises the risk of bowel cancer, a study involving researchers in Birmingham has shown.
Iron may interact with a faulty gene in the gut to trigger cancer, scientists said. Red meat contains large amounts of iron and is also known to increase the likelihood of bowel cancer.
The discovery could lead to new cancer treatments that target iron in the bowel.
In studies of mice, researchers found that susceptibility to bowel cancer was strongly influenced both by iron and a gene called APC. When the APC gene was faulty, mice with a high iron intake were two to three times more likely to develop the disease.
Mice fed a low iron diet remained cancer free even if the gene was defective. But when the APC functioned normally, high iron levels did no harm.
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Lead scientist Professor Owen Sansom, deputy director of the Cancer Research UK Institute for Cancer Research in Glasgow, said: "The APC gene is faulty in around eight out of 10 bowel cancers but until now we haven't known how this causes the disease. It's clear that iron is playing a critical role in controlling the development of bowel cancer in people with a faulty APC gene."
Each year, more than 41,000 people in the UK are diagnosed with bowel cancer and around 16,000 die from the disease.
Without a working APC gene, iron is allowed to build up in the cells lining the gut, said the researchers writing in the journal Cell Reports. This activates a genetic cancer "switch" called wnt that causes cells to multiply out of control.
Co-author Dr Chris Tselepis, a Cancer Research UK scientist at the University of Birmingham, said: "Our results also suggest that iron could be raising the risk of bowel cancer by increasing the number of cells in the bowel with APC faults.
"The more of these cells in the bowel, the greater the chance that one of these will become a starting point for cancer. We're now planning to develop treatments that reduce the amount of iron in the bowel and so could lower the risk of developing bowel cancer.