As backyard cookout season kicks into high gear, many people may be eyeing their sizzling burgers and dogs with suspicion. And for good reason: a number of studies published in the past two decades have turned up evidence that eating charred, smoked, and well-done meat could raise cancer risk—pancreatic, colorectal, and prostate cancers, in particular.
A 2010 review of the evidence on cancer and “well-done” meat, conducted by researchers at Vanderbilt University, concluded that “the majority of these studies have shown that high intake of well-done meat and high exposure to meat carcinogens, particularly HCAs, may increase the risk of human cancer.” Heterocyclic amines (HCAs), which some experts also refer to as heterocyclic aromatic amines (HAAs), are a class of chemical that forms in cooked red meat and, to a lesser extent, in poultry and fish, according to a 2011 study in the journal Chemical Research in Toxicology.
Another class of chemicals, called polycyclic aromatic hydrocarbons (PAHs), has also been linked to cancer. “PAHs are formed when fat and juices from meat grilled directly over a heated surface or open fire drip onto the surface or fire, causing flames and smoke,” according to a fact sheet published by the National Cancer Institute (NCI). “The smoke contains PAHs that then adhere to the surface of the meat.” Even if meat isn’t charred or cooked at high temps, smoking meat can increase its levels of PAHs.
Both HAAs and PAHs are metabolized by enzymes in the body. And some of the byproducts of this process can cause DNA damage that may contribute to the development of cancer, suggests the research of Robert Turesky, an expert in cancer causation at the University of Minnesota.
But there’s a lot of variance in how a given piece of grilled meat affects any individual person. “The concentrations of HAAs formed in cooked meats can vary by over 100-fold, depending on the type of meat, the method, temperature, and duration of cooking,” says Turesky. “In general, the highest concentrations of HAAs [are found] in well-done cooked meats, and in meats that are charred, such as by barbequing or flame broiling,”
Turesky’s research also indicates that a person’s genetic makeup may influence how they respond to the chemicals, and so “the risk of developing cancer for individuals who eat well-done meat may vary considerably,” he says.
Further, there’s mounting evidence tying the consumption of processed meats—such as hot dogs, bacon, and salami—with some of the same cancers studies have linked to grilled or well-done meat. It may be that individuals who eat a lot of charred steak or well-done burgers are also more likely than the average person to eat a lot of bacon or hot dogs. And so it could be the processed meat—not the blackened steak—that accounts for any increased cancer risks. “Sorting out what’s driving these associations is very hard,” says Dr. Stephen Freedland, director of the Center for Integrated Research in Cancer and Lifestyle at Cedars-Sinai Medical Center in Los Angeles.
Another challenge to the “grilled-meat-causes-cancer” narrative is that the real-world evidence linking the consumption of well-done meat to cancer is inconsistent. While that 2010 Vanderbilt study found “a majority” of studies have turned up a cancer connection, that majority was slim. Some studies have found evidence of increased cancer risk among people who eat a lot of grilled meat, but other studies have not found a significant association.
“Population studies have not established a definitive link between HCA and PAH exposure from cooked meats and cancer in humans,” according to the NCI. While studies in rodents indicate that these chemicals can cause cancer, “the doses of HCAs and PAHs used in these studies were very high—equivalent to thousands of times the doses that a person would consume in a normal diet,” the NCI’s fact sheet states.
Freedland’s take on the evidence is that eating a lot of charred meat—say, two to three meals a week for many years—could produce the kind of cellular damage that raises cancer risk. “But I don’t want people to be paranoid,” he says. “I worry a lot more about the desserts and soda people are having with their grilled meat.”
The sugar in these foods and drinks likely contributes to obesity, and obesity is a clear risk factor for cancer. “I think eating charred meat is probably not the best thing for you, but here and there, it’s probably okay,” Freedland says. He notes that grilling meat on tin foil and marinating it in herbs and spices may also reduce the development of potential carcinogens.
“Clearly, the risk [of eating charred meat] is far lower than for someone who smokes a pack of cigarettes a day or heavily imbibes alcohol,” Turesky says. “But many people who are meat-eaters consume low levels of these potentially carcinogenic compounds daily, and the exposure may add up over time.” He advises eating meat “in moderation,” and trying not to overcook or char meat.
Long story short, eating a blackened steak every night for dinner is probably imprudent if you’re worried about cancer. But enjoying the occasional burned burger or ribeye isn’t something you should stress about.
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