Remember the headlines a few weeks back, when the World Health Organization categorized red and processed meats as cancer-causing?
Turns out, the techniques you use to prepare your meat seem to play into this risk.
A new study published in the journal Cancer finds that high-temperature cooking methods may increase the risk of kidney cancer if you consume a lot of meat.
And other studies have found that high consumption of well-done, fried or charred meats is associated with an increased risk of colorectal cancer, pancreatic and prostate cancer.
"The lower-risk methods are baking and broiling," says Stephanie Melkonian, a post-doctoral fellow at the MD Anderson Cancer Center and a co-author of the new study in Cancer.
Other lower-temperature cooking techniques include sous-vide — which is used in some professional kitchens – and preparing meat in a Crock Pot or some other type of slow cooker. Or you can make a traditional pot roast, which skips the high-temperature searing process in favor of lower-temperature browning. This particular recipe cooks at 300 degrees.
If you listen to my story on Morning Edition, you'll hear chemistry professor Matthew Hartings of American University use a steak and a blowtorch to explain the chemical reactions that take place as meat is browned. Remember the Maillard Reaction?
Basically, as the outside of the meat browns up, and the temperature heats up, the chemical reaction creates lots of aroma and flavor compounds, some of which are molecules called cyclic amines. Harting says we evolved to like those flavor compounds. Think of it as an evolutionary nudge from our ancestors, who came to associate these smells as a sign that all nasty bacteria were cooked out.
But here's the potential downside: If you cook the meat too long, at too high a temperature, the chemical reaction keeps going, creating other compounds. Some of them, known as heterocyclic amines (or HCAs), can be carcinogenic when we consume them in high-enough concentrations.
As the National Cancer Institute explains, HCAs "have been found to be mutagenic — that is, they cause changes in DNA that may increase the risk of cancer."
To evaluate the association between cooking techniques and cancer risk, the researchers at MD Anderson documented the eating and cooking habits of people who'd been diagnosed with kidney cancer.
Then, they compared the kidney patients' habits with the habits of a group of healthy, cancer-free people.
"What we found is that the way [people] cooked [their meat] did matter," says Melkonian.
Those with cancer consumed more meat overall. And they were also more likely to pan-fry their meat at high temperatures, cook it over an open flame, or cook it until it was well-done or charred.
The study documented a nearly two-fold increase in the risk of kidney cancer associated with the intake of one particular type of HCA, known as MelQx, which is — according to the paper — "one of the most abundant HCAs commonly created in the grilling, barbecuing, and pan-frying of meats at high temperatures."
As the researchers write in the study, this suggests "that the intake of meat cooked at high temperatures may impact the risk of kidney cancer through mechanisms related to mutagenic cooking compounds."
It's important to point out that other possible mechanisms may explain the link between high consumption of red meat and increased cancer risks.
For instance, as the authors point out, "heme iron and N-nitroso compounds exposures, which were not measured in the current study, also may play a role." In other words: It's complicated.
And as the authors point out, future studies are needed to get a more complete understanding.