People who eat lots of red meat may have a higher risk of some types of kidney cancer, suggests a large US study.
Previous studies examining the link between red meat and kidney cancer arrived at mixed conclusions, according to Dr Carrie Daniel, from the National Cancer Institute in Rockville, Maryland, and her colleagues.
For their study they used data on close to 500 000 US adults age 50 and older, who were surveyed on their dietary habits, including meat consumption, and then followed for an average of nine years.
During that time, about 1 800 of them – less than half a percent – were diagnosed with renal cell carcinoma. Those cases included 498 clear cell and 115 papillary adenocarcinomas, the researchers reported online in the American Journal of Clinical Nutrition.
Association stronger for papillary cancers
On average, men in the study ate two or three grams of red meat per day, compared to one or two grams among women. Participants in the top quintile of red meat consumption – about 4g per day – were 19% more likely to be diagnosed with kidney cancer than those in the bottom quintile, eating less than one gram per day.
That was after accounting for other aspects of diet and lifestyle that could have influenced cancer risks, such as age, race, fruit and vegetable consumption, smoking and drinking and other medical conditions including high blood pressure and diabetes.
When the researchers looked at the most common types of kidney cancers, they found that the association between red meat and cancer was stronger for papillary cancers, but there was no effect for clear-cell kidney cancers.
People who ate the most well-done grilled and braaied meat – and therefore had the highest exposure to carcinogenic chemicals from the cooking process – also had an extra risk of kidney cancer compared to those who didn't eat meat cooked that way.
Limit red meat intake
Dr Daniel and her colleagues said more research is needed to figure out why red meat may be linked to some types of kidney cancers but not others.
But for now, meat-related cooking chemicals "can be reduced by avoiding direct exposure of meat to an open flame or a hot metal surface, reducing the cooking time, and using a microwave oven to partially cook meat before exposing it to high temperatures," said Dr Daniel.
"Our findings," she concluded, "support the dietary recommendations for cancer prevention currently put forth by the American Cancer Society – limit intake of red and processed meats and prepare meat by cooking methods such as baking and broiling."
(Reuters Health, December 2011)