I've heard that eating meat cooked at high temperatures, such as on a grill, can pose a cancer risk. Does burning toast do the same thing? C.D., Braintree, MA.
Probably not, but nobody really knows since burned toast isn't high on the research agenda.
Cooking muscle meats -- beef, pork, fowl, and fish -- above 400 degrees Fahrenheit creates chemicals that are not present in uncooked meats, according to the National Cancer Institute. Researchers found that people who ate meat medium-well or well-done had three times the risk of stomach cancer, compared to those who ate their beef rare or medium-rare.
Chemicals called heterocyclic amines (HCAs) are formed when amino acids (the building blocks of protein) from the meat and creatine (a chemical found in muscles) are cooked at high temperatures. HCAs are known carcinogens in animals, and may increase cancer risk in humans, though this has not been shown definitively.
Since bread doesn't contain creatine and it takes creatine to create HCAs, it's unlikely that cooking, or even burning, toast would create HCAs, said Marji McCullough, a nutritional epidemiologist at the American Cancer Society headquarters in Atlanta.
Other potentially carcinogenic chemicals in meat cooked at high temperatures are the PAHs, or polycyclic hydrocarbons, said Rashmi Sinha, an epidemiologist at the National Cancer Institute. They occur in the smoke created from burned fat. In theory, burned toast could have PAHs, said Sinha, but again, this has not been established.
One potential worry is a class of chemicals called acrylamides, recently established as probable carcinogens. Acrylamides are found in starchy foods exposed to high cooking temperatures, such as potato chips or French fries. ''Theoretically, acrylamides could be a problem in burned toast, too," said McCullough.
Bottom line? Scrape the burned stuff off your toast if it bothers you. But, so far at least, there's not much evidence that burned toast is a health hazard. Some people, Sinha among them, actually like their toast on the charred side. ''I always burn my toast, usually not deliberately," she said. ''I like it."