What you should know about burned foods and cancer risk

The question: Is it true that blackened or charred foods can cause cancer?

The science: Many of us love our seared steaks and grilled burgers and hot dogs. But when it comes to these blackened, charred and smoked meats, moderation is key, some experts said.

Some foods — particularly cooked meats — form compounds that may be carcinogenic under certain circumstances, including the type of meat, cooking temperature, method and duration, research shows. But there are ways to limit our exposure to these compounds.

When red meats, poultry or fish are grilled over a barbecue or pan-fried at high temperatures — higher than 300 degrees Fahrenheit — the amino acids, carbohydrates (or sugars) and creatinine in the muscle react to heat, forming compounds known as heterocyclic amines, or HCAs, particularly in the blackened or charred portions, experts said.

Similarly, when fat from meat being cooked over an open flame drips onto the fire or hot charcoal, polycyclic aromatic hydrocarbons, or PAHs, form. And the vapors get reabsorbed onto the surface of the meat, experts said.

These vapors also can be inhaled, so position the grill such that the wind does not blow them directly into your face while cooking, said Robert Turesky, a professor of medicinal chemistry and the Masonic Chair in Cancer Causation at the University of Minnesota.

Both HCAs and PAHs are metabolized by enzymes in the body, and the by-products, or metabolites, “can damage DNA and cause mutations leading to cancer,” Turesky said. “Fortunately, there are enzymes in our bodies that repair this DNA damage.”

Many of these compounds are mutagenic and carcinogenic and can cause certain cancers over time in laboratory animals.

But the degree of risk to humans is less certain. Epidemiological studies have not shown consistent associations between consuming blackened or charred meats and developing cancer, said Elizabeth Platz, a professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health.

For instance, a 2010 literature review reported that high intake of well-done meat “may increase the risk of human cancer,” and some studies have pointed to associations with increased risks of colorectal, pancreatic and prostate cancers. Other studies, however, have not found a notable link.

Another issue is meats that are blackened or charred are often red meats or processed meats that carry an even greater health risk, said Carrie Daniel-MacDougall, an associate professor of epidemiology at the University of Texas MD Anderson Cancer Center.

Those who eat these foods weekly or more often are at the highest risk, she said.

“There’s something to be said for doing things rarely or as a special treat versus making it a part of everyday life,” she said.

Blackened and charred meats are not the only foods to consider limiting.

Starchy foods cooked at high temperatures, such as toast or fried potatoes, including french fries and potato chips, can produce acrylamide, a chemical classified as a probable human carcinogen based largely on animal studies.

Studies in humans have shown mixed results. Some found no association, while others reported a link between high acrylamide dietary intake and a higher risk of certain cancers, including lymphatic and skin cancer in men and endometrial and ovarian cancer in women.

A difficulty in determining health risks for humans based on animal studies, Turesky said, is that many of the chemicals shown to cause cancer in animals are given at levels considerably higher than those formed in cooked meats — a 1,000 to a million times higher.

Less is known about the risks of tossing vegetables onto the grill, but Turesky noted that “any time you burn foods, char foods, you’re producing some chemicals that may be harmful.”

While cancer risks from eating blackened or charred foods are probably low, but not zero, for people who are healthy and eat them only in moderation, some experts said, it is important to consider your individual risk factors.

What else you should know

Here are some ways to limit potential exposure to these compounds, particularly HCAs and PAHs, according to the experts:

• Bake, roast or steam foods to avoid high heat and open flames. If grilling, avoid direct contact with flames to reduce the chance of charring, said Stephen Freedland, the director of the Center for Integrated Research in Cancer and Lifestyle at Cedars-Sinai Medical Center.

• Marinate meat before grilling. Marinades can help break down the muscle and other components necessary to form HCAs and PAHs, Daniel-MacDougall said. One study found that steaks marinated with products rich in antioxidants before grilling had much lower levels of carcinogens. Marinating “does not eliminate it. You can still form these compounds. But it’s a method of reducing that,” said Daniel-MacDougall, who was not involved in the study.

• Flip the meat more frequently on the grill to reduce the risk of charring.

• Consider eating a side salad with your meats. Some research suggests that eating cruciferous vegetables may be beneficial because they contain compounds called phytochemicals that activate enzymes that detoxify HCAs and PAHs, Turesky said.

• Limit intake of blackened or charred foods to avoid high levels of exposure.

The bottom line

For healthy individuals who consume blackened or charred foods in moderation, cancer risks are probably low, but not zero. While the degree of risk is not certain, many experts recommend limiting these foods.