https://www.washingtonpost.com/national/health-science/evidence-grows-linking-grilled-meat-and-cancer-but-you-can-lower-the-risk/2017/06/02/f946078c-4549-11e7-a196-a1bb629f64cb_story.html
More than 34,000 cancer deaths are caused around the world each year by diets high in processed meat, according to data referenced in the IARC report. By comparison, tobacco causes about a million cancer deaths annually. Alcohol consumption causes 600,000. And air pollution is responsible for 200,000.
Studies show several ways that meat might cause cancer, says Loic Le Marchand, an epidemiologist at the University of Hawaii Cancer Center, who collaborated with more than 20 international scientists on the IARC report. One line of evidence points to compounds called nitrates and nitrites, which are used during processing and also form in the colon when people digest meat and meat products, even those labeled “nitrate-free.”
Cooking methods make a difference, according to studies that have zeroed in on two groups of chemicals that appear in particularly large quantities when meat, fish or poultry is cooked under high heat by grilling, barbecuing, boiling or even pan-frying. One group, called HAAs (heterocyclic aromatic amines), form during high-temperature reactions between substances in muscle tissue. PAHs (polycyclic aromatic hydrocarbons), which form when meat is smoked, charred or cooked over an open flame, are also found in tobacco smoke.
In general, Turesky says, higher temperatures and longer cooking times lead to higher levels of HAAs and PAHs. Enzymes in our bodies then change these chemicals into compounds that can damage DNA. Numerous studies have illustrated that kind of damaging potential in cell cultures and animals, including rodents and primates.
