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Microwave Ovens – a Hot Issue

Posted by Didi Gorman on

Microwave ovens. Such an integral part of modern life. Used daily in most households in the USA, this simple kitchen appliance has polarized opinions like no other before.

In this article we’ll explore different aspects of this modern, yet controversial invention.

To avoid confusion, the term ‘microwave oven’ will refer to the kitchen appliance, whereas ‘microwave’ will refer to the form of radiation.

Let’s start at the beginning.

A Bit of History

The year was 1945. World War II had just ended.

Percy Spencer, an American engineer from Maine, was working on an active radar set when he suddenly noticed that a candy bar he had in his pocket had started to melt. He suspected the melting had to do with the high-power microwave beam he’d been working with, and, excited by this accidental discovery, he proceeded to deliberately cook popcorn this way, and then cook an egg using the same method. Unfortunately for a colleague who was standing nearby, the egg exploded in his face. 1

It took much more experimenting - and many more exploding eggs - before commercial and residential applications of this discovery were developed in later years. Large scale use started in the 70’s and 80’s.

Let’s Get Technical


The microwave oven is defined as a “kitchen appliance that heats and cooks food by exposing it to microwave radiation in the electromagnetic spectrum.” 1

The term ‘microwave radiation’ (or simply ‘microwave’) refers to a form of radiation called ‘non-ionizing’, meaning it can change the position of atoms but not alter their structure. Visible light, waves from radio or television, cellular phones and electric blankets are some examples of this type of radiation. 2

How Does the Microwave Oven Work?

Inside the microwave oven there is a tube called a ‘magnetron’ (combination of magnet and electron), that generates a type of energy called ‘microwave’, with a frequency of about 2,450 mega Hertz (MHz) and a wavelength of about 4.8 inches -about the width of your head. 2

Materials containing water (or water particles), such as foods, fluids or tissues, readily absorb microwave energy, which is then converted into heat due to thepowerful molecular friction of the water molecules inside the food. 3

A fan and a rotating plate help distribute the heat inside the oven.

What is the Difference Between Microwaving Food and Cooking in a Conventional Oven or on a Stove Top?

According to the World Health Organization (WHO): “The main difference between these two methods of cooking is that microwave energy penetrates deeper into the food and reduces the time for heat to be conducted throughout the food, thus reducing the overall cooking time.” 3

But as we shall see, not everybody agrees that this is the only difference. For now, let’s explore the advantages of the microwave oven.


It’s no secret that the microwave oven is fast. It is also convenient, affordable, and small.

Suitable for a tight budget, in a small kitchen and when in a hurry, it even saves washing up the dishes, as we can heat our food straight on its plate! (or in its container in the case of a ready-made meal).

We shouldn’t underestimate the importance of convenience. We live in a modern world where so many demands are made on our time: work, kids, classes, activities, you name it. We have enough on our plates as it is. An appliance that saves us some precious time and takes some load off our shoulders is definitely appreciated.

But there are two sides to the coin. And hand in hand with the benefits come the hazards.

A question that is often raised is: Is it safe? Or are we somehow compromising our food or our health on the altar of convenience?


Roughly speaking, we can divide the hazards into three main categories: heat related, radiation related, and toxin related.

Heat related hazards

Before you jump in and say that heat related hazards also exist with a conventional oven or a stove top -and you are right - please consider the following:

One peculiarity of microwave cooking is that food may heat unevenly, depending on the amount of food being heated, its density, consistency, and water content.

And when food heats unevenly, we may well end up with some of it very hot and some undercooked.

Burn injuries

Since water molecules heat up rapidly when subjected to microwave energy, which may result in uneven heating, food heated in this way can be very (VERY!) hot even if it doesn’t seem so. Especially if its consistency is uneven (which means it has some dryer parts and some moister parts. Fruits or veggies would usually be more moist).

So you want to use caution and handle with care.

Also, you really want to watch out when boiling water. Unlike on the stove where you can see the steam escaping and bubbles forming, there may not be steam or bubbles when water boils in the microwave oven (because it may not have an escape), but the water may still super-heat and boil suddenly. 3

The World Health Organization adds that “only dishes and containers specifically designed for microwave cooking should be used. Certain materials, such as plastics not suitable for the microwave oven, may melt or burst into flames if overheated.” 3

Undercooked food

“Microwave energy does not penetrate well in thicker pieces of food. This can lead to a health risk if parts of the food are not heated sufficiently to kill potentially dangerous micro-organisms.” 3

It is therefore recommended to let the food “rest for several minutes after cooking [in the microwave oven] is completed to allow the heat to distribute throughout the food.” 3

Accidental food explosions

Remember the story about Percy Spencer’s experiment with the egg? The one that exploded in his colleague’s face?

“Another peculiarity of microwave cooking relates to the thermal response of specific foods.

Certain items with non-porous surfaces like hotdogs, [that do not allow liquid or air to pass through], or composed of materials that heat at different rates (e.g. yolk and white of eggs) heat unevenly and may explode. This can happen if eggs or chestnuts are cooked in their shells”. 3

Radiation related hazards

Radiation is at the heart of the controversy surrounding the safety of using the microwave oven.

Is radiation a problem?

The experts disagree.

Radiation Leakage

According to the World Health Organization, provided that the microwave oven is in good condition, not damaged, altered or dirty, the door and interlocks shut properly, and it is used according to the manufacturers' instructions, “the design of the microwave oven ensures that the microwave energy is contained within the oven and can only be present when the oven is switched on and the door is shut. Leakage around and through the glass door is limited by design to a level well below that recommended by international standards. However, leakage could still occur around damaged, dirty or modified microwave ovens” 3, in which case the microwave oven should not be used.

And, “To dispel some misconceptions, it is important to realize that food cooked in a microwave oven does not become ‘radioactive’. Nor does any microwave energy remain in the cavity or the food after the microwave oven is switched off.’’ 3

Dr. Joseph Mercola, a health and wellness expert, thinks differently. According to Dr. Mercola, even when the microwave oven works properly, when it’s running, it may still increase the microwave levels in the kitchen significantly, and even beyond the wall if the microwave oven is against an inside wall. 2b

This type of exposure may affect the eyes, the heart, and may be even linked to Leukemia. One should therefore keep well away from the microwave oven when it’s running, especially children and pregnant women. 2

In addition, “Powerwatch, a non-profit independent organization with a central role in the microwave radiation debate, states that we don't really know if the current regulations about leakage are truly safe, and recommends ovens be checked at least annually, since microwave emissions can change with normal use.” 2b

Nutrient Depletion

Does nuking food in the microwave oven harm its nutrient value any more than a conventional oven or a stove top?

According to the World Health Organization: “Food cooked in a microwave oven is as safe, and has the same nutrient value, as food cooked in a conventional oven.” 3

However, according to Dr. Mercola, other studies comparing the two methods resulted in more nutrient loss when the food was microwaved, and they “generally agree, for the most part, that microwaving food damages its nutritional value.” 2

Dr. Mercola adds: “Microwaving zaps the nutrients right out of your food” and “turns your beautiful, organic veggies, for which you've paid such a premium in money or labor, into ‘dead’ food.” 2

Molecule deformation

Some studies have shown that “microwave heating and conventional heating are very different on a molecular level.” 2c Microwaving may distort and deform “the molecules of whatever food or other substance you subject to it.” 2

Toxin Leach Out

According to Dr. Mercola, “Another problem with microwave ovens is that carcinogenic toxins [a substance able or likely to cause cancer] can leach out of your plastic and paper containers/covers, and into your food.” 2 BPA, benzene, toluene and xylene are just a few examples. 2a

So to nuke or not to nuke?

While experts disagree and evidence so far is not entirely conclusive, it is our view that the microwave oven should be avoided whenever possible.

We simply don’t trust it.

Our ancestors used fire and put pots above it. And while we do not expect anyone to start a bonfire when they make supper, we do think that the conventional oven, stove top and even the toaster oven are more in keeping with traditional ways of cooking and provide a more natural source of heat than radiation.

Admittedly, breaking free of your microwave oven may require some changes in your routine, but the main change, we find, is in perception:

It is not only what you eat, but how you make it. We should therefore be conscientious regarding our cooking methods.

Here are a few simple and useful tips, by Dr. Mercola, on how to break free of your microwave oven:

Breaking Free of Your Microwave Oven: A Few Basic Tips 2

  • Plan ahead. Take your dinner out of the freezer that morning or the night before so you don't end up having to scramble to defrost a 5-pound chunk of beef two hours before dinnertime.
  • Make soups and stews in bulk, and then freeze them in gallon-sized freezer bags or other containers. An hour before meal time, just take one out and defrost it in a sink of water until it's thawed enough to slip into a pot, then reheat it on the stove.
  • A toaster oven makes a GREAT faux-microwave oven for heating up leftovers! Keep it at a low temperature — like 200-250 degrees F — and gently warm your food over the course of 20-30 minutes.
  • Prepare your meals in advance so that you always have a good meal available on those days when you're too busy or too tired to cook.

One last thought

The microwave oven is certainly a hot issue - no pun intended. And whereas we believe we should all make informed decisions regarding food choices and food quality, it is equally essential to consider the way we prepare our food. After all, we all seek to benefit the most from our nutrition.


1. Wikipedia, the free encyclopedia ‘Microwave oven’

    Why Did the Russians Ban an Appliance Found in 90% of American Homes?

    2a. ibid, The January/February 1990 issue of Nutrition Action Newsletter
    2b. ibid, “Microwave oven and microwave cooking overview," Powerwatch
    2c. ibid, Penn State University. "DNA and the microwave effect" posted from MailBag (April 8, 2002)

3.World Health Organization
    Electromagnetic fields & public health: Microwave ovens