People who eat lots of red meat may have a higher risk of some types of kidney cancer, according to a U.S. study of thousands of adults.
Researchers writing in the American Journal of Clinical Nutrition found that middle-aged adults who ate the most red meat were 19 percent more likely to be diagnosed with kidney cancer than those who ate the least.
A higher intake of chemicals found in grilled or barbecued meat was also linked to increased risk of the disease.
"Our findings 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," said lead researcher Carrie Daniel, at the U.S. National Cancer Institute.
Previous studies examining the link between red meat and kidney cancer arrived at mixed conclusions, so Daniel and her colleagues used data from a study of close to 500,000 U.S. adults age 50 or older to take another look at the issue.
The group was surveyed on their dietary habits, including meat consumption, and then followed for an average of nine years to track any new cancer diagnoses.
During that time, about 1,800 of them -- less than half a percent -- were diagnosed with kidney cancer.
On average, men in the study ate two to three ounces (57 to 85 grams) of red meat a day, compared to one or two ounces among women. Participants with the highest consumption of red meat -- about four ounces (113 grams) per day -- were 19 percent more likely to be diagnosed with kidney cancer than those who ate less than one ounce per day.
That was after accounting for other aspects of diet and lifestyle that could have influenced cancer risks, including age, race, fruit and vegetable consumption, smoking and drinking, and other medical conditions such as high blood pressure and diabetes.
The association between red meat and cancer was stronger for so-called papillary cancers, but there was no effect for clear-cell kidney cancers.
People who ate the most well-done grilled and barbecued meat -- and therefore had the highest exposure to carcinogenic chemicals that came out of the cooking process -- also had an extra risk of kidney cancer compared to those who didn't cook much meat that way.
The study doesn't prove that eating red meat, or cooking it a certain way, causes kidney cancer. And, said Mohammed El-Faramawi, an epidemiologist from the University of North Texas Health Science Center in Fort Worth, some people who eat lots of red meat won't develop kidney cancer, while others who hardly eat any will.
"Red meat is an important source of iron, it has protein," added El-Faramawi, who did not work on the study, noting that eating a limited amount of meat while following dietary guidelines is a good idea.
"You should not stop eating red meat because there is an association between red meat and renal cancer."
Daniel said that more research is needed to figure out why eating red meat is linked to some cancers but not others.
But for now, she said, meat-related cooking chemicals can be reduced by reducing the cooking time for meat, by avoiding direct exposure of meat to an open flame or hot metal surface, and by using a microwave oven to partially cook meat before exposing it to high temperatures.
Get all the latest news and videos in your inbox. Register FREE