Cooking over an open flame is an ancient practice predating the emergence of our species. Picture: Oupa Mokoena

Washington - Grilling meat is a tradition worldwide, but it’s not the healthiest thing to do. A growing body of research suggests that cooking meat over a flame is linked to cancer.

Combusting wood, gas, or charcoal emits chemicals known as polycyclic aromatic hydrocarbons. Exposure to these so-called PAHs is known to cause skin, liver, stomach, and several other types of cancer in lab animals. Epidemiological studies link occupational exposure to PAHs to cancer in humans. When PAHs from a flame mingle with nitrogen, say from a slab of meat, they can form nitrated PAHs, or NPAHs. NPAHs are even more carcinogenic than PAHs in laboratory experiments. The reasonable conclusion is that grilling meat may be hazardous to your health.

The evidence linking cancer to cooking meat over a combustion source has been accumulating for decades.

Epidemiologists first noticed a connection between the consumption of smoked foods and stomach cancer in the 1960s. Japan, Russia, and Eastern Europe, where smoking is a popular way to preserve meat and fish, became laboratories for gastric cancer research.

Newer studies suggest that eating smoked meats may lead to cancer even outside the gastrointestinal tract. A 2012 study, for example, linked smoked meat consumption with breast cancer.

From a 1950s perspective, cigarettes were not so different from eating grilled or fried meat. In subsequent decades, it has become clear that smoking is not the only problematic cooking method.

Frying bacon, for example, produces significant levels of PAHs, probably because of volatilisation of carbon in the bacon itself. An Iranian study published last year found that people who developed certain kinds of gastrointestinal cancers were more likely to have a diet high in fried rather than boiled foods. (The researchers linked levels of browning to cancer incidence, thus reducing the likelihood that oil consumption was the culprit.)

The US Food and Drug Administration and the WHO also remain concerned about the presence in food of acrylamides, a known carcinogen that forms from sugar and amino acids when cooked at high temperatures. Long-term studies are under way. The worrying implication is that cooking foods at high heat, even without active combustion, may be dangerous.

None of these studies is definitive. It is possible that other variables account for the correlations between cancer and cooking over a flame or at high heat, or that the carcinogenicity of PAHs observed in animal studies overstates the risk. But the risks are worth taking seriously.

The question is: Now what? Giving up high-heat cooking is a radical idea. Cooking over an open flame is an ancient practice predating the emergence of our species. It may have practically created modern humans.

The smell and taste of charred meat whisper to our primordial selves; cooking over a charcoal grill evokes the safety and community of gathering around a fire. It’s almost more instinct than tradition. Even the researchers who study PAHs stop short of recommending prohibitions on high-heat cooking. Staci Simonich, an Oregon State toxicologist who identified several new NPAHs last week, said: “Everything in moderation.”

But the evidence suggests that huddling around a heat source and searing our food is a habit we should at least consider breaking. Before you accuse me of madness or subversion, let me lay out the case. This argument, like so many discussions about cancer, begins with tobacco.

In the mid to late 19th century, doctors determined that lip and tongue cancer rates were higher among smokers of pipes and cigars. Despite this link, major medical journals mocked those who opposed smoking.


Insurance company statisticians first noticed the correlation between smoking and lung cancer in the 1930s, followed closely by Nazi physicians, who established the connection by the end of the decade.

Hitler vehemently opposed smoking as a risk to public health long before his Allied counterparts did. Two British doctors finally convinced the Anglo-American medical establishment that smoking caused lung cancer in a landmark article in the British Medical Journal in 1950.

The statistics were soon piling up in both the United Kingdom and the US, but the general consensus that a few cigarettes per day were harmless remained intact for many years.

It wasn’t until 1964 that the report of the Surgeon General of the US finally and firmly declared that smoking was indisputably linked to the surge in lung cancer.

Granted, the risk-reward equation for smoking differs from that of grilling or frying meat. Eating is a fact of life, and grilled and fried meats are a major part of the standard diet in many parts of the world. And the link between PAHs and related substances and cancer is nowhere near as clear as the link between tobacco and cancer.

Giving up grilled, smoked and fried meats seems bizarre today, but population-wide changes in dietary staples have dramatically affected cancer rates in other parts of the world. In the early 1970s, liver cancer killed nearly one in 10 adults in Qidong, China, a region located at the mouth of the Yangtze River. Two factors contributed to the astonishingly high prevalence: widespread infection with Hepatitis B, and food contaminated with aflatoxin.

The soil in Qidong did not support rice cultivation, so the population relied on maize. Growing and storage conditions encouraged the growth of a mould that produced the potent carcinogen. When food trade between regions opened up, the residents of Qidong largely switched to rice. By the late 1980s, exposure to aflatoxin in the area had dropped more than a hundredfold, and the liver cancer rate has halved.

So, should you throw your charcoal grill away? The evidence may not be there – yet. The Environmental Protection Agency is developing relative potency factors to define the cancer risk of exposure to PAHs, but it is difficult to clearly define the carcinogenicity of an activity like grilling and eating a steak.

Blasting animals with carcinogens in a laboratory environment is easy enough, but human exposures to PAHs are complicated by differences in ventilation and cooking temperatures, among other variables, and the effect of PAHs is almost certainly mediated by factors such as other foods in the diet and genetic diversity. – Slate