Washington - Firing up the grill to cook some juicy meat over a hot flame is a summer pleasure.
Charring pork, beef, fish and poultry is a good way to kill bacteria, but studies show that high heat and flames can create potentially cancer-causing compounds.
But how dangerous are these chemical compounds, really? Are they harmful enough to reconsider our love of grilled meat?
When I posed those questions to Rashmi Sinha, deputy branch chief at the National Cancer Institute, she hedged. Numerous studies have linked chemicals in grilled meat to cancer, she says, but the evidence is circumstantial and it's not clear how much you would have to eat to substantially increase your risk.
Cooking meat at high temperatures produces two main types of compounds with cancer-causing potential: heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs). At high temperatures, the amino acids, sugars and other compounds in meat undergo chemical reactions that generate HCAs, while PAHs emitted from flames or smoke stick to the surface of the meat.
Much of the research linking HCAs and PAHs to cancer comes from studies in which laboratory animals were fed the compounds at levels thousands of times greater than people would get from a normal diet. Researchers can't ethically feed these chemicals to people to see what happens, Sinha says, so they compare people who were exposed to more of the compounds with those who had less. “You ask people about their eating habits, so it's not a direct measure,” she says.
In one such study, Kristin Anderson at the University of Minnesota School of Public Health and colleagues looked at the eating habits of more than 60 000 people, 208 of whom were diagnosed with pancreatic cancer over a nine-year period. The researchers found that those who reported the highest consumption of meat cooked at high temperatures had a 70 percent greater risk of developing pancreatic cancer than those with the lowest intake; colorectal and prostate cancer have also been linked to grilled meat consumption.
While more studies are investigating HCAs and cancer in humans, the link is still not definitive, Anderson says.
Figuring out whether grilling meats poses a cancer risk is more challenging than it might seem. For starters, HCAs and PAHs must be metabolised by specific enzymes in the body to become dangerous, and people have varying levels of these enzymes. It's also difficult to accurately measure how many HCAs and PAHs people consume, Anderson says. In part, this is because there's no easy way to estimate the levels of these compounds in any particular serving of food: That depends on factors such as how the meat was cooked and how much meat people actually ate.
Imagine that you were asked to recall how often you'd eaten grilled meat in the past six months, how large the portions were and how hot the grill had been: How confident would you be in your response? Your answer suggests why population studies are not seen as hard proof.
If grilling meat does pose a danger, the best way to reduce your risk, of course, would be to cut meats out of your diet, or at least stop cooking them on high heat. But if you're not ready to give up the grill, adopting a few tricks will reduce your exposure to HCAs, Anderson says. Microwaving ground meat for two to three minutes and pouring off the juices before cooking can reduce the precursors of the carcinogens, she says. Another good strategy is to employ some patience and not expose the food to direct heat, “particularly the flames lapping at the meat,” she says. Don't char or burn meat, and cut off burned portions.
You never want to eat undercooked meat, but it's not a bad idea to avoid overcooking. A 2012 study found that well-done meat had 3 1/2 times the amount of HCAs that medium-rare meat did.
More tips: Wrap your meat in foil to protect it from smoke. If you can, cut away fat before grilling. “Taking away the fat is good, because it drips onto the hot surface, which causes more smoke and flashing,” Sinha says.
Some studies have suggested that certain marinades - those containing rosemary, for instance - might reduce the production of HCAs, but whether this reduces cancer risk isn't clear, Sinha says. “You might reduce one [type of HCA] but increase another one, and we don't know which are the worst.”
Given all these uncertainties, it's impossible to declare how much grilled meat is safe, Sinha says. She recommends moderation: Eating meat from the grill every day is clearly much riskier than eating it once a month, she says, “but I can't give you a number where it goes from okay to bad.”
Washington Post