Microwave ovens aren’t causing colon cancer, despite social media claims

PolitiFact | Experts say food should be cooked in containers marked for their use.
In this April 8, 2008, file photo, salesman Hank Pham puts the price on a General Electric microwave oven in the appliances section of Howard's Appliance and Big-Screen Superstore in San Gabriel, Calif.
In this April 8, 2008, file photo, salesman Hank Pham puts the price on a General Electric microwave oven in the appliances section of Howard's Appliance and Big-Screen Superstore in San Gabriel, Calif. [ KEVORK DJANSEZIAN | AP ]
Published Feb. 4

Microwave ovens are used to heat up Hot Pockets and leftovers in pretty much every American home today.

People have been buying them for their homes since 1967 and myths that the devices can cause cancer have lingered for decades. Research has debunked them, but the claims persist.

A Jan. 27 Instagram post kept with that tradition: “Doctors say colon cancer is on the rise due to toxins absorbed while cooking food (in) the microwave.” it warned.

This post was flagged as part of Facebook’s efforts to combat false news and misinformation on its News Feed. (Read more about PolitiFact’s partnership with Meta, which owns Facebook and Instagram.)

Colorectal cancer, which starts in either the colon or rectum, is the third-most diagnosed cancer in the United States each year, with about 150,000 cases, the American Cancer Society said.

The rate of colorectal cancer among Americans overall has been dropping for decades, possibly because of increased screenings and better health habits, the American Cancer Society said.

Although the rate is decreasing in people older than 50, the colorectal cancer rate among Americans younger than 50 has risen steadily since the 1990s, though it is still rare. That has led groups to issue new guidelines lowering the age for recommended screenings to 45.

Rebecca Siegel, a cancer epidemiologist and senior scientific director of surveillance research at the American Cancer Society, said the rate of colorectal cancer per 100,000 people younger than 50 has increased from 4.8 in the mid-1990s to 8.4 in 2019. That’s a 75% increase.

“The cause of the trend is unknown but likely due at least in part to a less healthy diet and more sedentary lifestyle,” said Siegel.

Pamela Kunz, an associate professor of internal medicine at Yale University and member of the American Society of Clinical Oncology’s Cancer Communications Committee, said there are likely many reasons behind colorectal cancer increase in younger adults, including genetic risks, environmental factors and lifestyle factors, including diet.

But microwave ovens aren’t to blame, experts we spoke with said.

“There is no evidence that microwave ovens cause colon cancer or any other type of cancer via any mechanism,” said Kunz.

Timothy Jorgensen, a professor of radiation medicine at Georgetown University, agreed with Kunz, saying, “Radiation from microwave ovens has never been shown to cause cancer of any type, nor has food prepared in microwave ovens.”

The ovens work by producing microwaves, a type of low-level nonionizing radiation deemed relatively harmless. The microwaves are absorbed by the food, causing water molecules in the food to vibrate, producing heat and cooking the food. They do not make food radioactive or contaminated, said the U.S. Food and Drug Administration, which is charged with regulating microwave ovens.

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People should use only containers or plates labeled as microwave-safe to heat their food, as some plastic or foam containers not designed for microwave use could melt and leak chemicals into food, according to VeryWell Health and others.

Groups such as the World Health Organization and the American Society of Clinical Oncology have also stated there is no cancer risk from food cooked in microwave ovens.

Jorgensen, the author of “Strange Glow: The Story of Radiation,” said he has seen no recent studies linking colon cancer and microwave ovens. If a study were to link the two, Jorgensen said, it would be hard to show whether the association was because of microwave cooking or the processed foods they are typically used to heat.

“Processed foods, particularly processed meats, have been strongly linked with colon cancer,” he said. “So, any association between colon cancer and cooking in a microwave oven would need to account for the types of foods that are being heated in microwave ovens.”

There are many colorectal cancer risk factors, including obesity, smoking, alcohol and a diet low in fruits and vegetables and high in red meats or processed meats, according to the Centers for Disease Control and Prevention, the American Society of Clinical Oncology, and many others, but none of them mentioned microwave ovens.

Our ruling

An Instagram post said a rise in colon cancer is because of toxins absorbed when food is cooked in microwave ovens.

The rate of colorectal cancer cases in the U.S. has steadily decreased over the past two decades, although it has risen in Americans younger than 50. It’s unclear what’s causing that increase, but experts say there’s no evidence linking it to microwave-cooked food.

We rate this claim False.