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Is microwaving safe?

NUTRISPEAK by Vesanto Melina MS, RD

Portrait of  Vesanto Melina

• Many of us wonder if microwave ovens are sending us to the cancer ward or creating weird molecules in food that our bodies can’t handle. Most Canadian homes have microwaves so they obviously have wide appeal. But what do we know of their health implications? How does microwaving affect nutrients in food?

This cooking method originated when engineer-inventor Percy Spencer was building radars in the 1940s and found that microwaves melted the candy bar in his pocket. Seven years later, the first “radarange” – seven feet tall, 700 pounds – was used at a Boston restaurant. The name was changed to “microwave oven” and a small unit was introduced for home use in 1967. In that era, women were entering the workforce and timesaving kitchen devices were welcome.

Microwaves are produced when a magnetron tube converts an electric current to electromagnetic (EM) radiation, similar to radio or light waves. When this interacts with food molecules, heat is generated and food is cooked, starting from the inside. Microwaves can travel through glass, but are reflected from metals, thus doors have a metal screen. Microwave ovens have a better cooking efficiency (57%) than electric convection (17%) or gas convection (9%) ovens. Conventional cooking heats food from the outside by convection (baking), radiation (broiling) or conduction (frying) and the heat gradually travels inward.

The pluses

Surprisingly, microwave ovens cause less nutrient destruction than the more lengthy heating processes involved in baking, boiling or steaming. All cooking involves loss of vitamins and protective phytochemicals, yet among your options, microwaving can result in minimal losses.

When food is boiled, nutrients are leached into the water, which is often discarded. Thus boiling vegetables can strip more nutrients than microwaving. Protein is not damaged unless there is overcooking and that can happen with any form of heating. Microwave food the minimum time, with little or no cooking water.

Compared with toasting, baking, barbequing and frying, microwave cooking produces fewer carcinogens such as nitrosamines or the AGEs (Advanced Glycation End products), which give the desired browning, but are toxic.

Microwaves offer people with limited skills or time the opportunity to eat some nutritious meals and less junk food.

The minuses

Early microwave ovens leaked excessive EM radiation. Today’s versions prevent leakage and result in less exposure than people get from cell phones. Yet we absorb EM radiation from power lines, cell phones, airplane flights, computers, fridges and more. Norbert Hankin of the Environmental Protection Agency says, “The real question remains whether there could be cumulative effects.”

Over time, seals on microwave doors can lose effectiveness. Exposure to radiation is highest within two inches of the microwave so don’t stand in front of it watching your food rotate. Place the microwave away from high traffic areas.

Many plastics, when heated, release toxic and hormone-disrupting compounds into the food. Don’t microwave (or heat by other methods) food in plastic or Styrofoam.

Microwave-free options include heating water in an electric kettle and using a toaster oven. And leftovers don’t always need reheating; they often taste fine cold. For maximum nutrition, choose a raw or high-raw diet.

Vesanto Melina is a local registered dietitian and co-author of bestselling nutrition books including Becoming Raw. Contact info: 604-882-6782,,,

One comment

  1. Juanita /

    Hi Vesanato,

    I enjoy reading your article in the Common Ground. I had just briefly researched this topic after asking for a toaster oven in the staff room at work. There are no peer reviewed studies saying microwaves are damaging to our health, yet. I have read so many books and articles in my life that have warned against microwaves. With cell phones and the influx of technology in our world currently, are we losing touch with reality? Or were all those previous warnings just fear mongering? I love raw food and I understand all cooking destroys nutrients to some degree. You say protein is not affected more than overcooking any other way. Microwaving seems so far removed from a pot over the fire, I have difficulty believing it is as safe as you say. That being said, I respect your opinion and am writing because you have peeked my curiosity. P.S. I do not own a cell phone but I love talking to people.


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