For many American families, Memorial Day marks the official opening of barbeque season. Although grilled meat is regarded as traditional American fare — and humans have been grilling food since fire was discovered — frequently eating grilled meats can increase the risk of certain types of cancers.
While the risk is relative — it could be more dangerous to drive on a holiday weekend, for example — there are easy ways to reduce exposure to carcinogens when cooking outdoors. Plus it’s good to know the science involved in high-heat cooking.
When meats are grilled, broiled, or seared, the high cooking temperature breaks down the amino acid creatine (an amino acid found in muscle), forming chemicals called heterocyclic amines (HCAs). The federal government added HCAs to its list of known carcinogens in 2005. Some of the highest concentrations of HCAs are found in grilled meats, according to a 2003 study published in the International Journal of Food Science and Technology. Grilling meat provides the right conditions for HCA formation because more HCAs are produced the longer and hotter the meat cooks.
Since HCAs are mutagens, they can bind directly to DNA, causing the kind of mutation that can promote formation of cancerous cells. Studies have linked frequent ingestion of HCAs to an increased risk of pancreatic and colorectal cancers. Regularly eating charred, well-done meat may increase the risk of pancreatic cancer by 60 percent, according to a University of Minnesota study, so scrape off any charred bits before serving.
“There is some evidence that consuming red meat — whether it’s grilled or not — increases the risk of colorectal cancer,” said Bonnie Liebman, director of nutrition for the Center for Science in the Public Interest.
Liebman cited a National Institutes of Health (NIH) study that tracked the meat consumption of half a million members of the AARP (American Association of Retired Persons) over 10 years. The study found that people who ate five ounces of red meat a day (about 1.5 Quarter Pounders) had a 30 percent higher risk of dying of cancer. Conversely, those who consumed an average of two-thirds of an ounce per week were on the low end of the risk spectrum.
Prior to the NIH-AARP study, Swedish researchers examined 15 studies and found that red-meat eaters have a 28 percent higher risk of colorectal cancer than those who eat little or no red meat.
Although chicken and fish have long been regarded as healthier alternatives to beef and pork, the grilled versions of these meats pose increased or comparable risks of HCA exposure. Grilled chicken produces 10 times more HCAs than those recorded in grilled beef, according to a Cancer Project study, sponsored by the Physicians Committee for Responsible Medicine. In grilled chicken, practically all the detected HCAs were in the form of PhIP, one of the carcinogens linked to an increased risk of breast cancer.
According to the Cancer Project study, the top five grilled meats recorded with the highest concentrations of HCAs (in order of highest concentration to lowest) are chicken breast, steak, pork, salmon and hamburger. Fish usually contains high levels of creatine, the amino acid responsible for increased production of carcinogens. For this reason, grilled salmon produces more HCAs than grilled hamburger meat, according to the Cancer Project study.
Grilling meat can also produce other types of food mutagens such as polycyclic aromatic hydrocarbons (PAHs), according to the Agency for Toxic Substances and Disease Registry. When grilling or broiling meat, the fat can drip into the open fire or electric heating element, which produces smoke and flames containing PAHs. The PAHs then bind to the surface of the meat, forming higher concentrations of PAHs the longer and hotter the meat is cooked. Choosing lean cuts instead of high-fat varieties, plus trimming fats and removing the skin from salmon and poultry is recommended.
Studies have linked the frequent consumption of grilled and broiled meat to the development of stomach cancer, according to the American Institute of Cancer Research. Liebman said that while these studies do show strong correlation between grilled meat and increased cancer risk, correlation can’t determine causation. Conducting these studies is not an exact science.
“You can’t say that these studies show that your risk of cancer will definitely increase if you eat grilled meat,” Liebman said.
For example, she said, in the NIH-AARP study, the researchers tried to control for as many variables as possible, such as weight, education, smoking, and vitamin intake. However, it’s hard to determine whether red-meat eaters have a higher cancer risk because they eat red meat or because the healthy lifestyle choices generally differ between those who frequently eat red meat and those who eat less or none at all, she said.
To reduce the risk of cancer, meat-lovers need not forego grilling altogether. Instead, avoiding the blackened or burned parts of meat can lower the risk of exposure to HCAs. Obviously, eating grilled meat less frequently and eating smaller portions of grilled meats will also reduce the risk of cancer.
Frequently flipping meat helps, Lieberman said. Cooking meat six minutes on both sides instead of 10 minutes on one side can cut HCAs by 70 percent by keeping the surface temperature lower, she said. Because piercing meat with a fork can cause drips and flare ups, use tongs or a spatula instead.
Cooking meat in a microwave for one to two minutes and pouring off the juices can remove 90 percent of the HCAs. However, Lieberman said, this often leaves the meat dry and not as appetizing. Marinating meat can also significantly reduce the production of HCAs. A tip sheet from Purdue University suggests marinades that contain anti-oxidants (vinegar, citrus juices, herbs, spices and olive oils) will help inhibit the formation of carcinogens on grilled meat.
Keeping the meat moist generates fewer HCAs. Boiling, steaming, poaching or stewing meat does not form HCAs because the temperature of the meat cannot increase past the boiling point.
Grilling non-meat alternatives is usually a safe bet against exposure to HCAs, because the formation of HCAs depends on the presence of creatine, which is mostly found in muscle tissue. Studies show that grilling vegetables, fruits and soy products do not yield HCAs, or only produce levels too insignificant to pose a health threat. Certain vegetables like broccoli and Brussels sprouts may help detoxify the liver of HCAs. Grilled alternatives to meat include portabella mushrooms, veggie burgers, fruit like pineapple, and kabobs that are light on the meat and heavy on the vegetables.
“Eating grilled meat once in a while probably isn’t going to do much harm,” Lieberman said. “But there are those people have the easy-to-use backyard grills who are grilling every other night. For them, the risk might be higher.”