Microwave Ovens

It has become common slang to “nuke” a meal, but microwave ovens do not make food radioactive or utilize any kind of nuclear reaction. Microwaves are in the same electromagnetic class as radio waves. X-rays and nuclear radiation are millions of times more powerful. If you were to heat up your burrito with nuclear fission, it would vaporize along with the rest of your neighborhood.

There is no evidence that microwave-safe plastics pose a health concern.

Heating plastic does increase the opportunity for chemicals to migrate into food. Avoid soft plastic containers such as margarine tubs, not only because they allow toxic substances to leach into food but because picking up melted plastic can cause a severe burn. Look for the words “microwave safe” or the symbol of a tiny microwave oven on containers and plastic wraps. The FDA acknowledges that some microwave-safe plastics allow for a small amount of substance to leach, but only at low levels deemed within a safe range for consumers. Safer still are containers made of inert, heat-resistant glass.

You can test plastic containers yourself as directed in microwave user manuals. Place the empty container in the microwave and run the oven on high for 30 seconds. If the container becomes hot with nothing in it, don’t use it.

Conventional ovens cook away more nutrients than microwaves do.

High temperatures and long cooking times lead to the evaporation of moisture from conventionally cooked food, and that water within the food contains nutrients. Even when vegetables are boiled, some minerals and vitamins are lost as they seep into the water and disappear in steam. The difference may not make or break your daily nutritional requirements, but microwave cooking generally preserves more nutrients.

Super-heated water can “erupt,” but it’s very rare.

This phenomenon results from water being overheated beyond its 212-degree boiling point. A pocket of super-heated water can build up below the surface, such that the water does not appear to be boiling. Moving the cup or adding a foreign substance (e.g., coffee, tea, sugar) then causes the water burst into a full boil—with dangerous consequences.

Uncommon as it may be, super-heating is more likely to occur in a very clean cup, such as one that’s come straight out of the dishwasher. Reduce risk by adding a pinch of coffee or tea before heating the water. You can also put a microwavable spoon in the cup beforehand. Stop the microwave to stir once, and do not overheat.

Contrary to popular opinion, microwaves do not heat food from the inside out. Neither do they heat evenly, which can lead to cold spots and hot spots. Turntables inside the oven will help, though you’ll still want to stir larger portions half way through a cycle. Uneven heating explains why you can’t count on a microwave to kill kitchen germs that accrue on a sponge: Bacteria and fungi can survive in cooler pockets.

Studies have shown it’s unsafe to heat breast milk or formula in a microwave for the same reason. The temperature might seem just right when you test a few drops on your wrist, but pockets of hot milk could scald a baby’s mouth or throat. Likewise, heating jars of baby food may leave the outside edges deceptively cool to the touch. Transfer baby food to a dish before heating, and be sure to stir and test before feeding it to the little one.

Safety standards minimize the risk of microwave exposure.

Little research has been completed on the long-term effects of low-level microwaves on humans. Since microwaves have been in wide use since the ’70s, it is assumed there is little risk that someone will heat up leftovers and then grow a fin.

Admitting a lack of data, the FDA enforces radiation safety standards to limit the allowable amount of microwaves that can leak from an oven. Microwaves made after 1971 are limited to 5 milliwatts of microwave radiation per square centimeter at about 2 inches from the oven surface. According to the FDA, this amount of exposure is far below the level known to harm people.

To reduce exposure further, stay farther from the oven when it’s running. Keep the seals along the door and inside edge clean to ensure a tight close. If your microwave was manufactured before 1971, retire it to the family museum.

Microwave Ovens is based on information provided by the U.S. FDA Center for Devices and Radiological Health and the FDA Center for Food Safety and Applied Nutrition.

Confused by health myths and misinformation? Each week, Rich Maloof talks to leading health experts to bring you the straight facts on a broad range of health topics.

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