By Emily Sohn June 3 at 8:30 AM
When cooked at high temperatures or over open flames, according to accumulating evidence, compounds in red and processed meats undergo biochemical reactions that produce carcinogenic compounds capable of altering the eater’s DNA.
Grilled vegetables don’t harbor the same risks.
The case for meat as a cancer risk has been building for decades, with plenty of studies showing that people who report eating diets heavy in red and processed meats have higher risks of certain types of cancer, as well as heart disease and other chronic illnesses. Enough of those studies — together with lab work — have built up to make a convincing case that meat carries risks, according to a 2015 analysis by the World Health Organization’s International Agency for Research on Cancer, which considered more than 800 studies conducted around the world.
Overall, the IARC review found that the strongest evidence linked processed meats (such as hot dogs, beef jerky, bacon and ham) to colorectal cancer — with each hot-dog-size serving of processed meat eaten daily raising the risk by 18 percent over a lifetime.
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.
The IARC review also found evidence for an association between unprocessed red meat (such as beef or pork) and colorectal cancer, along with some evidence that red meat might contribute to pancreatic and prostate cancers, too.
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.
Turesky is beginning to turn up evidence that it might. In a study published last year, he and colleagues studied biopsies of prostate tumors and found that DNA in the cancer cells had been damaged by HAAs.
“This is the first unequivocal proof that, once you eat the cooked meat mutagens, some of them find their way to the prostate and damage the prostate,” Turesky says. The study doesn’t prove that meat caused the cancer, he adds. “It could just be an association. Now we have to show that the mutations are attributed to the chemicals in cooked meat.”