How can burned food cause cancer

Chemical found in burned food that is carcinogenic

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Scientists are constantly gathering new knowledge about the links between food and cancer.

The International Journal of Cancer recently published a study suggesting that frequent consumption of very hot tea could increase the risk of esophageal cancer. Other studies warned against consuming red meat, which has been linked to an increased risk of colon cancer, and consuming sugary foods that serve as fuel for cancer cells.

Even the way we process food can have a huge impact on our health.

For more than 15 years, scientists have wondered whether the consumption of acrylamide - a chemical found in burnt, charred and roasted foods - negatively affects human health. Foods with a higher acrylamide content include coffee, french fries, and grain products such as toast and muesli.

Since acrylamide was only recently discovered in food, it is not yet clear whether it causes cancer. But the latest studies now shed light on the potential risk.

What is acrylamide and does it cause cancer?

The discovery of acrylamide goes back about two decades.

In the late 1990s, workers in the Hallandsas Tunnel in Sweden suffered from nausea, dizziness and numbness in their fingers. Shortly afterwards, the fish in the rivers near the tunnel died and cows that had drunk this water suffered from paralysis.

Scientists discovered that the workers and animals had been exposed to the chemical acrylamide, which had gotten into the soil and water during construction.

In 2002, scientists found that acrylamide is also present in starchy foods like bread, cookies, and potato chips. Today it is found in more than a third of the calories consumed in Europe and the US.

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Food that is fried, baked, or roasted at high temperatures goes through a process called the Maillard reaction: it turns brown, like the golden crust on a baguette or the charred outside of a toasted marshmallow. This reaction can form small doses of acrylamide.

So far, studies have shown that acrylamide only causes cancer in rats and mice exposed to the chemical in much higher doses than would be the case in humans. In the latest risk assessment, the Institute of Food Science and Technology found that the results of these animal studies “indicate a health problem”.

Food safety officials have particularly expressed concern about the presence of acrylamide in baby food, as children are more sensitive to cancer-causing chemicals than adults. A 2012 Polish study found that some infants are exposed to the chemical a dozen times more often than the population average.

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The International Agency for Research on Cancer lists acrylamide as "likely carcinogenic," but says the relationship between cancer and foods containing acrylamide is still being researched.

In March, a collaborative study led by the organization found that acrylamide can produce genetic signature mutations in humans that can lead to cancer. In a press release, the study's lead author said that "future research may ultimately provide a solid rationale for reducing acrylamide exposure in the general population."

California stores warn against acrylamide

California issues cancer warnings for all kinds of items, from boats to wooden furniture to Tiffany lamps.

Last year, a California judge ruled that Proposition 65 - a policy requiring companies to warn residents of significant exposure to toxic chemicals - coffee companies must issue warnings about acrylamide.

The California Office of Environmental Health Hazard Assessment is now trying to reverse this decision, as coffee consumption does not pose a significant risk. This effort is supported by the US Food and Drug Administration, which stressed that the cancer warnings "mislead consumers rather than inform".

More than a decade ago, restaurant chains like McDonald’s, KFC, Wendy's and Burger King agreed to post warnings about acrylamide in french fries in their California stores. In Great Britain, McDonald’s uses methods that are supposed to guarantee a lower occurrence of the chemical, such as preparation at lower temperatures or switching to potatoes with less starch.

In 2008, Heinz and Frito-Lay settled California state lawsuits after agreeing to reduce acrylamide levels in their products. The then Attorney General Jerry Brown called the deals "a victory for public health and safety".

The acrylamide dose makes the poison

A general principle of toxicology is that the dose makes the poison. Exposure to extremely high amounts of chemicals can make us sick, but an occasional serving of french fries or a cup of coffee is unlikely to kill us.

"Adults with the highest consumption of acrylamide could ingest 160 times as much and would still be at a level at which, according to toxicologists, it is unlikely that more tumors will form in mice," said David Spiegelhalter last year.

As with any chemical, new evidence could change our understanding of its relationship to cancer.

In the 1980s, every product that contained the calorie-free sweetener saccharin called "Sweet'N Low" had to carry a cancer risk warning. These concerns were based on a single study of saccharin exposure in rats, which turned out to be flawed: The rats used in the experiment were already prone to a parasite that made them particularly susceptible to bladder cancer. Following this discovery, the US Department of Health removed saccharin from its list of carcinogens.

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Since the risks of acrylamide ingestion are not fully understood, new studies may determine both that the chemical is harmful and that it poses no risk to human health at all. For now, we shouldn't worry about cancer roasting marshmallows or ordering french fries - but keep an eye out for future research.

This text was translated from English by Nora Bednarzik.