Do Microwaves Cause Cancer? (And 3 Other Microwave Myths)

In the United States, 97% of households have a microwave. But what misconceptions about our microwave use persist? Let’s take a look at 4 microwave myths that science has proven false.

Sabrina Stierwalt, PhD
Episode #281

image of a microwave

In 1946, an engineer was working near a piece of equipment known as a magnetron which is part of a radar system when he noticed that the radar emission at microwave frequencies melted the snack bar he had stashed in his pocket. Legends disagree as to whether it was a peanut cluster bar or a chocolate one, but the fact remains that rather than just mourning the loss of his snack, he did a little investigating.

He and his coworkers realized that focused beams of microwave emission—that’s waves of energy at frequencies near the radio frequency regime—will cause polar or electrically asymmetric molecules like water in food to rotate. This rotation produces thermal energy (aka heat) which then can quickly and nearly uniformly heat the food.

The microwave was born and dinnertime around the world saw a revolution. The first thing those engineers tried to cook was popcorn. The second thing was an egg which, of course, exploded in their faces. 

Now, according to the US Census Bureau, 97% of households in the United States have a microwave. But how much does the average household understand how a microwave works? What misconceptions about our microwave use persist? Let’s take a look at four microwave myths that science has proven false.

Myth #1: Due to the high temperatures, a microwave heats food all the way through to the center.

Anyone who has tried to reheat a frozen burrito in the microwave knows this myth can’t possibly be true. In fact, the air inside a microwave remains at room temperature, unlike in a conventional oven which takes longer to heat the surrounding air. This air temperature difference is also why your food never comes out of the microwave lightly browned & crispy.

The US Department of Agriculture estimates that microwaves only penetrate food down to 1 to 1.5 inches below the surface. Anything thicker than that will have to be heated through conduction of heat from the outer layers of the food toward the center. Thus, cutting that burrito in half at some point in the microwaving process will increase its surface area and allow for more uniform heating.

Microwave cooking does destroy bacteria just as a conventional oven will, but bigger health issues arise when the microwave is used to cook foods like raw meat for the first time and those foods are not heated thoroughly. So while a cold spot in your leftovers can lead to a disappointing lunch, cold or raw spots in meat that is not already cooked can be unsafe.

Myth #2: Microwaving food removes its nutrients.

While it is true that some nutrients, like Vitamin C for example, do break down when exposed to heat, this isn’t solely a microwave cooking issue, but rather can occur no matter how that food is heated. In fact, food typically spends less time in a microwave which means there are fewer opportunities for those nutrients to break down. Microwaves can also have the upper hand over other cooking methods because they use less water which is known to leach nutrients out of vegetables, like when they are boiled.

So we can’t use the microwave as an excuse not to eat our vegetables as it might be doing an even better job at keeping those nutrients locked in our food. In fact, an albeit unsuccessful defamation lawsuit was even brought against the producers of the movie "American Hustle" because Jennifer Lawrence’s character says she read an article by science writer Paul Brodeur claiming that microwave cooking removes nutrients from foods. (Brodeur, not wanting to be associated with the scientifically unsupported argument, was the one who sued for defamation.)

Myth #3: Microwave radiation causes cancer.

For some people, the term radiation carries with it a bad reputation when all it means is energy that is emitted by a source. Radiation comes from our bodies in the form of heat. The sunlight that keeps us warm and allows us to navigate the outdoors during the daytime is also radiation.


About the Author

Sabrina Stierwalt, PhD

Dr. Sabrina Stierwalt is an extragalactic astrophysicist at the California Institute of Technology and Adjunct Faculty at the University of Virginia.

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