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Are microwave ovens safe & nutritious? Or just convenient?

Leah Landry

Over the last several decades, microwave ovens have become a standard kitchen appliance in many American homes. But for some, doubts remain about their safety and impact on the nutritional value of food cooked in them.

This week on “Take Care,” food scientist Don Schaffner takes us behind the microwave door to explain how microwave ovens work, and the ways this kind of cooking technology interacts with food. Schaffner is an extension specialist in food science and distinguished professor at Rutgers University. He is a world-renowned expert on food safety and protection and is the co-host of a podcast on microbial food safety.

How do microwave ovens work?

Microwaves use short radio waves, or “micro” radio waves.

The way that a microwave oven works is it uses microwave energy to essentially vibrate the water molecules in that food and the vibration causes the food to rise in temperature,” said Schaffner.

Contrary to what some people think, microwaves do not use radiation.

The differences between microwave cooking and using a stove or oven or another method is really just in the way the heat is applied to the food.

“All microwave energy is doing is heating the food. Whether you boil that water in a microwave or in a teakettle on the stove, there’s no difference. That water is getting hot because you’re putting energy in it.”

Are microwaves dangerous?

Yes, and no.

“Those waves heat the food but they can also damage you, which is why if you look into your microwave oven, you can see it’s not a clear piece of glass that you have to look through. There’s actually some shielding that stop those waves from getting out into the room from cooking you or cooking your dog or your cat as they’re walking around the kitchen,” said Schaffner

But Shaffner says as long as you have a properly-made microwave oven, it will not pose a health and safety risk to you, your children, or Fluffy and Fido, for that matter. Can you have a poorly manufactured oven that can cause problem? Yes, says Shaffner, but just in the same way any defective appliance could cause harm. And Shaffner points out the Federal Trade Commission is around to help protect consumers from products that are poorly made.

Does cooking your food in a microwave make it less nutritious?

Shaffner says, in fact, studies show that some foods are more nutritious if cooked in a microwave than if cooked by other methods.

For example, more vitamin C is retained in vegetables cooked in the microwave than if they are boiled on the stove. If you boil vegetables, the vitamin C gets leached into the water, and that health value literally goes down the drain.

In general, Shaffner says, the lower amount of heat that is applied to food, the more nutrient retention. And because microwaves cook food faster than other methods, the food often holds on to more nutrients.

Do microwaves kill bacteria that can be in food?

Shaffner says one downside to microwaves is that they heat food in a spotty way. So he says your microwave must have turntable or you must rotate your food partway through the cooking process to make sure you kill dangerous bacteria throughout the food if any exist.

What kind of cookware is safe to use?

Make sure that the container you are using, whether it’s glass or plastic, is designed to be used in a microwave, Shaffner says. If it’s a plastic container and not microwave-approved, Shaffner says the plastic can leach into the food. That doesn’t cause short-term problems, but can be harmful in the long run.

Take-home containers from restaurants can be a big culprit, Shaffner says, because you don’t know if it’s microwave safe or not. So, he recommends transferring your doggie bag to one of your own bowls.

Simply put: “Don’t put it in microwave if you don’t know it’s microwave safe,” says Shaffner.