A new medical study links high consumption of red and processed meats to an increased risk of different forms of cancer. Health experts already knew red meat increased the risk of colon cancer. Now researchers have found an increased risk for a number of other cancers, as well.
Researchers at the National Cancer Institute wanted to know which cancers other than colon cancer might be more common among big red meat eaters. To find out, they analyzed questionnaires from over a half-million men and women over the age of 50.
In questionnaires, people answered questions about their lifestyle, including what kind of meat they ate, and how often.
Epidemiologist Amanda Cross headed the eight-year study. During that time, she says, a little more than 53,000 cancer cases were diagnosed in the group.
To analyze the relationship between eating meat and cancer, Cross divided people into five groups, from the biggest meat eaters down to those who ate the least amount of meat, including a few vegetarians.
Red meat included all types of beef, pork and lamb. Processed meats included cold cuts and luncheon meats, as well as sausages, bacon and hot dogs — beef as well as turkey hot dogs.
"On a diet of 2,000 calories a day, which is average for a man," Cross said, "the lowest category of red meat was equal to three thin slices of ham or less, per day, and the highest category was approximately equivalent to 10 thin slices of ham, or a quarter-pounder or a small steak or pork chop a day."
As expected, Cross found more cases of colon cancer among the big meat eaters. But she also found about the same increase in lung cancer with big meat eaters, as well as increases in cancers of the esophagus and liver. Among men, there was an increase in pancreatic cancer.
Researchers speculate that cancer results from several chemical compounds that are found in the meat itself. But they also believe some of the compounds develop during the process of cooking.
"Compounds that are formed during high-temperature cooking techniques have been shown to damage DNA in animal and in vitro studies," Cross said.
Robyn Curran, a dietitian at Cedars Sinai Medical Center in Los Angeles who works with cancer patients, says results from studies like this don't necessarily mean people should stay away from red meat altogether.
"In general, we don't recommend necessarily excluding red meat from your diet unless (it's a) personal choice," Curran said. "It does have a lot of good attributes, like iron and B vitamins, protein and so forth — particularly if leaner meats are selected."
If people do choose to eat red meat, Curran says they should avoid high-temperature cooking like barbecuing and pan-frying, which cause cell-damaging compounds to form.
Grilling meat over a direct flame results in fat or meat juices dripping onto the hot fire. That creates flames that contain the harmful compounds, which can then adhere to the surface of the food. That process can happen with chicken and turkey as well as red meat.
"That's why we recommend if you're barbecuing, take particularly chicken, for example, you may want to microwave it halfway cooked, and then put it on barbecue," Curran said. "You don't want to cook it the whole duration, because that really increases the risk of these compounds forming, which are known carcinogens."
Curran says those who eat red meat should try to limit themselves to 8 to 11 ounces per week — the equivalent of about three hamburgers total.
The results of the research study led by Cross were published in the latest issue of PLoS Medicine.