'More research needed' after scientists suggest well-cooked meat affects bladder cancer risk
US scientists have suggested a link between eating well-done meat and a slightly increased risk of bladder cancer. But a Cancer Research UK spokesperson urged caution over the results.
The research, presented at the annual meeting of the American Association for Cancer Research, also suggests that people with certain genetic variants may be susceptible.
Scientists at the University of Texas MD Anderson Cancer Centre conducted a 12-year study, in which they looked at 884 people with bladder cancer and a further 878 cancer-free volunteers.
Participants were divided into four groups, depending on the amount of red meat they ate.
The researchers discovered that people with the highest intake of red meat were almost one-and-a-half times more likely to develop bladder cancer than those who only ate a small amount.
A significant association was seen between consumption of steak, pork chops or bacon and bladder cancer. And chicken and fish, when fried, were also found to raise a person's chances of developing the disease.
Further analysis revealed that people who ate well-done meat were almost twice as likely to develop bladder cancer than those who ate their meat rare.
The researchers then gave extra questions to 177 bladder cancer patients and 206 cancer-free volunteers to determine their intake of heterocyclic amines (HCAs) - chemicals that form when meat is cooked at high temperatures and that have previously been linked to cancer.
They found that people with the highest estimated intake of three particular HCAs were more than two-and-a-half times more likely to develop bladder cancer than those with the lowest intake.
Furthermore, the researchers showed that people with the highest intake of red meat and who also had seven or more faults in genes involved in the metabolism of HCAs were almost five times more likely to develop bladder cancer than those who ate the smallest amount.
Lead author Dr Xifeng Wu, professor in MD Anderson's Department of Epidemiology, said that the study "reinforces the relationship between diet and cancer".
"These results strongly support what we suspected - people who eat a lot of red meat, particularly well-done red meat, such as fried or barbecued, seem to have a higher likelihood of bladder cancer. This effect is compounded if they carry high unfavourable genotypes in the HCA-metabolism pathway," he said.
But Dr Alison Ross, Cancer Research UK's senior science information officer, was more cautious about the results.
Dr Ross said: "The link between diet and cancer is complex and difficult to unravel, but we know that eating lots of red and processed meat can increase our risk of some types of cancer.
"More research is needed before we can say for sure whether or not regularly eating red meat affects bladder cancer risk, and if the way it is cooked has an impact. For now, our advice remains to eat a balanced diet that is low in fat, processed and red meat, and rich in vegetables, fruit and fibre."
Dr Ross added: "Smoking is the most important preventable cause of bladder cancer, so giving up is the best way to cut your chances of getting the disease."