“Every time I nuke leftovers in the microwave, my roommate freaks out and leaves the room. She says it not only leaks radiation, but destroys the nutrients in food and makes it carcinogenic. That can’t be true, can it?”
Although a cursory Google search will turn up numerous, and frightening, claims that the microwave oven is harmful to food and/or human health, those claims are unfounded. A common fixture in home kitchens, office pantries, hotel rooms, airplanes, convenience stores, and, yep, restaurants for decades, the microwave is still distrusted by many. Perhaps that’s because of the use of words like nuke and zap, or because radio waves, unlike a gas flame or the glowing coils of an electric stove, are invisible when they heat up food. You might think it sounds like magic, but no—it’s physics.
And so I turned to the Health Physics Society—a nonprofit organization that promotes radiation safety in scientific, medical, research, industrial, and technical areas—for a crash course in microwaves, which are a form of electromagnetic radiation; that is, they are waves of electrical and magnetic energy moving together through space, like radio waves, which are less powerful. “Microwaves have two characteristics that allow them to be used in cooking: they are absorbed by foods and they pass through glass, paper, plastic, and similar materials,” the website states. “Microwaves are produced inside a microwave oven by an electron tube called a magnetron. The microwaves bounce back and forth within the interior until they are absorbed by food. Microwaves cause the water molecules in food to vibrate.”
And the more those water molecules vibrate, the more heat (a.k.a. thermal energy) they create. That heat is what cooks the food, which is why foods high in water content, like fresh vegetables, can be cooked more quickly than other foods.
As far as nutrition goes, because microwave ovens cook food faster and with little added fat or water, the food retains more nutrients than other forms of cooking. In a 2010 Food Politics blog post, nutritionist Marion Nestle calls it like she sees it: “Eat a mixture of cooked and uncooked vegetables and the vitamins will take care of themselves. If you do cook, steaming is great and microwaving is better for preserving vitamin activity.” Most vitamins are heat stable, but if you are particularly interested in vitamin C, Nestle goes on to make the point that for that vitamin, “raw wins every time.”
Nutrition aside, do microwaves, in fact, leak radiation? Technically, yes, but don’t get your knickers in a twist. Microwaves are a non-ionizing form of radiation: Their frequency is so low they don’t have enough energy to damage the DNA in our cells. Other sources of non-ionizing radiation include the infrared lamps that keep food warm in restaurants, radios, televisions, and the computer screen you are staring at right now.
And the level of microwaves (which lose intensity very quickly) that might be released from microwave ovens is pretty minute. According to the FDA’s Center for Devices and Radiological Health, which regulates microwave-oven safety, the amount of radiation any unit made after 1971 can possibly leak throughout its lifetime is five millowatts per square centimeter at roughly two inches away from the oven—that is, if they can manage to get beyond the metal mesh–lined door that stops microwaves in their tracks, so to speak. Manufacturers must also use a door latch that, when released, automatically shuts off the microwaves.
“But where does all this cancer business come from?” a friend asked reasonably. She was in luck, because I’d just unearthed a back issue of the Nutrition Action Newsletter, published by the Center for Science in the Public Interest, the consumer advocacy organization for food safety that was just last week given top marks by Food Safety News.
Back in April 2005, in a piece titled “Microwave Myths,” David Schardt traces the spurious charges back to unsubstantiated research by Swiss food chemist Hans Hertel (who, with seven other vegetarians, spent two months in a hotel consuming milk and vegetables cooked in a microwave, as well as other ways) in the late 1980s, and U.S. researcher William Kopp, who wrote a 1996 piece about the fact that Cold War research in the Soviet Union had proven the dangers of microwave ovens. Although the Soviet Union may have banned the ovens for a short period, Schardt reports, no countries ban them today. “The ‘evidence’ that microwaved foods cause cancer boils down to Hans Hertel’s and William Kopp’s claims,” Schardt goes on to say.
And bona fide research by Dr. James Felton of the UC Davis Cancer Center (who was also, at the time, at the Lawrence Livermore Radiation Laboratory, in Livermore, California) comes to the opposite conclusion. “Grilling or frying meat or poultry can create heterocyclic amines, which may cause cancer.”
Schardt explains, “When Felton and his colleagues briefly microwaved meats and drained off the juices before grilling, most of the precursors of those potential carcinogens were lost along with the juices.” (Food. Chem. Toxicol. 32: 897, 1994)
Schardt’s piece also dispels other microwave myths, including the safety of various wraps, containers, and packaging, and he gives some great tips on cooking, reheating, and defrosting as well. Handy stuff. And if you are even more curious about actual microwave cooking (as opposed to popping popcorn or melting chocolate), check out Modernist Cuisine at Home, the more-user-friendly version of the six-volume instant classic Modernist Cuisine, by Nathan Myhrvold, physicist and authority on the science of contemporary cooking. There’s a whole chapter on microwave ovens, and I, for one, can’t wait to expand my culinary horizon.