Whether you call it the microwave or the oven, the process of taking food from the fridge and reheating it in the microwave is a simple, time-saving trick that many of us rely on, with a time-saving advantage.

Microwave cooking is a convenient way to prepare food. Unfortunately, not everyone agrees that it is safe to use the oven-based method for reheating food. The debate about how microwaves affect health is still ongoing, but there are some very credible researchers who do not participate in this discussion.

Many people with a fitness routine don’t like cooking in the microwave at all. They fear that the microwave will destroy the nutrients. This affects the quality of the food. Poisons our bodies.

Is any of these statements true? Should we be worried about cooking in the microwave (or reheating)? In this article, we will find out the truth.

  • Unprocessed foods.
  • Whole foods.
  • Local food.
  • Food cooked in the microwave.

What’s different from the others?

What is the purpose of the microwave when we use it?

Do we use it to reheat leftover uncooked food from a recipe we made after shopping at the farmer’s market? Or do we use the microwave to make the Pop-Tart as good as possible?

Up to 93% of American households own and/or use a microwave, making it very attractive.

But do we know anything about the long-term health effects of continuous use of microwaves? Does cooking food in the microwave affect the nutrients it contains?

How microwave ovens came to be

Percy Spencer built a radar in the 1940s and discovered that the microwaves from the radar melted a chocolate bar in his pocket.

Seven years passed, and in 1947 we first tasted Radarange in a Boston restaurant. It weighed about 700 pounds and cost about $5000. People didn’t like cooking with a radar, so the name was changed to microwave.

The first popular microwave oven for domestic use was introduced in 1967.

With more and more women working, anything that could save time in the kitchen was welcome. The advertising campaign coincided with the beginning of the use of microwave ovens by housewives, after which young saleswomen traveled throughout North America promoting their benefits.

Original patent for a microwave oven

How microwave ovens work

Indoor cooking

In traditional cooking, heat is transferred to the outside of the food by convection (frying), radiation (roasting) or conduction (frying). This heat is then released into the product. This can take some time, as anyone who has ever desperately tried to roast a half-thawed turkey can attest.

Microwaves, on the other hand, start inside the food.

Microwaves are a form of electromagnetic energy (radiation), like radio waves or light waves. When the energy absorbed by the microwave interacts with the food molecules, heat is released and the food is cooked (imagine rubbing your hands together quickly).

The radiation source in a microwave oven is a microwave tube that converts electric current into electromagnetic radiation. Microwaves can pass through glass, but metals reflect them. This is why the doors of microwave ovens are fitted with a metal grid.

Energy consumption

Because microwave ovens heat food from the inside out (rather than from the outside in), their efficiency (the percentage of energy that heats the food during cooking) is higher than that of electric or gas convection ovens.

Furnace type Efficiency
Microwave 57%
Electric convection oven 17%
Gas convection oven 9%

Microwave ovens also use less electricity than conventional electric ovens.

Furnace type Watt
Microwave 750-1100
Toaster 1200-1700
Electric oven 3000-8000

Effects of microwaves on foodstuffs


You may have heard that microwaves kill food, but that’s not entirely true.

Microwave ovens do not normally destroy the nutrients in food. And in some cases, cooking in the microwave can even help preserve nutrients.

Any form of cooking drains nutrients from food, especially when food is cooked in large amounts of water for long periods of time. Boiling carrots, for example, can remove many more nutrients than microwaving, because the nutrients in the carrot can be washed away by the boiling water.

However, since we have not yet discovered all the constituents in food, we will probably never know all the effects of microwave exposure on nutrients.


The quality of the protein when heated in the microwave seems to be good. There is evidence that amino acids and vitamin B12 can be converted into inactive forms.

On the other hand, the availability of certain amino acids can be improved because there is no surface tanning. And heating in the microwave can destroy the trypsin inhibitors in the beans. Bonus!

Breast milk

Cooking breast milk in the microwave destroys the antibodies and vitamin B12 (this also happens with normal cooking, but it takes about 25 minutes or more).

Speaking of bodily fluids: Microwaving blood for transfusion can cause haemolysis (but has not been shown to damage DNA).

Food safety and carcinogens

Microwave cooking produces fewer nitrosamines and EFAs in meat than traditional cooking methods. For more information on AGE, click here.


Taste preferences are individual. However, restaurants do not usually mention microwaved green beans on their menus.

When cooking in the microwave, there is no drying or browning reaction on the surface, which changes the taste and appearance of food (especially meat and bread).

Some microwave products are equipped with a grey plate for reheating. This box contains a very thin metal covering of a tough plastic film that absorbs microwave energy and converts it into heat for browning. To achieve this effect, certain additives can be applied to the surface of the food. My God, now I have memories of microwave pizza in high school.

Health effects of microwaves

1980s. Micro-machines, slap bracelets, American gladiators and Hans Hertel.

Wait a minute, wait a minute. Who is Hans Hertel? Hertel and Bernard Blanc, two Swiss scientists, have conducted several experiments with microwave cooking.

They found that the subjects had lower hemoglobin levels, higher white blood cell counts, and higher blood cholesterol levels after eating microwaved foods. However, these data have never been published in a peer-reviewed journal.

The Swiss equipment industry was not happy with these results and sued the scientists. Hertel and Blanc were convicted of commercial impairment, but the conviction was later overturned (see Background section for more details).

Electromagnetic radiation

When the first microwave ovens appeared on the market, tests showed that they allowed excessive amounts of electromagnetic radiation through. This kind of radiation is non-ionizing, which means it’s not the kind of radiation associated with Homer Simpson and Chernobyl – it’s in the form of waves.

Early microwave ovens operated at wavelengths similar to those of many modern telephones (915 mHz). The main difference between phones and ovens is that the power needed to run a microwave oven – about 1,000 watts – is much higher than the power needed to run a cell phone. Mobile phones work with less power, but at the same wavelength as microwaves.

In the US, the FDA allows some radiation leakage. In the 1970s, Consumer Reports magazine declared that microwave ovens were inadvisable, and the Soviet Union banned microwave ovens for a time (today they are not banned in any country).

Radiation exposure is highest within two inches of the microwave oven. However, the amount of electromagnetic radiation to which we are exposed when cooking in a microwave oven is smaller than that from mobile phones (measured cumulatively).

When our bodies absorb microwaves, we are absorbing energy in the form of heat. Some tissues are sensitive to it.

Strong electromagnetic radiation fields can increase the risk of cancer, affect the nervous system and contribute to other problems (e.g. Alzheimer’s disease). There is a link between microwave cooking and oral cancer/salivary tumors, but this could be due to the production of heterocyclic amines in the food.

There is evidence that cooks are at increased risk of developing cancer as a result of microwave exposure, but the evidence is not yet clear.

If we were only exposed to electromagnetic frequencies when we cook food in a microwave oven, it probably wouldn’t matter much. But when you add up the total impact, it becomes a cause for concern.

We absorb electromagnetic radiation from power lines, cell phones, airplanes, computers, refrigerators, etc. There is growing evidence that the effects of microwaves increase over time.

However, the radiation from microwave ovens is so low that it should not damage DNA. And there is no reliable data to suggest a direct negative effect of microwave ovens on human health.

We do not have a clear position on the possible health risks of exposure to microwaves because the research is inconclusive. The question remains whether there can be a cumulative effect.
-Norbert Henkin of the Environmental Protection Agency’s (EPA) Center for Science and Risk Assessment.


Many plastics release toxic and endocrine disrupting substances into food when heated. Therefore, do not put food in plastic in the microwave, especially plastic containers that are not marked as suitable for microwave use. And polystyrene… Well, don’t go.

There is mixed support for the term safe microwave – some say it is legal, others that it is unregulated. Exposure to heat of any kind (oven, microwave, fire, etc.) has the same negative effect on plastic. The microwave only speeds up the process.

And it’s unlikely that most of us would use Tupperware as a frying pan. (At least not after the… unfortunate… incident).

Dyes are not approved for microwave use. So don’t think you’re off the hook if you use paper towels or colored paper packaging.


Food heated in the microwave may have an uneven temperature distribution. The food (or part of the food) that contains the most water heats up the fastest. That’s why many oven models are equipped with a turntable: It distributes the waves more evenly.

Uneven food temperatures can allow microorganisms such as Salmonella, Listeria, Clostridium difficile and Campylobacter to survive.

So when you cook or reheat food, make sure it is heated well and, if possible, turned or stirred from time to time.

Large Explosive Teacup

Heating liquids in the microwave can prevent the formation of air bubbles. Water can overheat to the boiling point.

If the liquid is stirred (e.g. by stirring or dipping in a tea bag), it can ignite. So be careful not to put your tea on the volcano.

Summary and recommendations

Microwave ovens do not normally destroy the nutrients in food. If using the microwave helps you eat more nutritiously and less junk food, keep it.

However, too much electromagnetic frequency can have harmful effects, and one way to limit exposure is to avoid the microwave.

When using a microwave oven:

  • Do not heat food in plastic.
  • Make sure the food has a temperature of 160 degrees F throughout (you have a food thermometer, right?).
  • Cover the food to ensure even cooking.
  • Let the dish stand for a few minutes after cooking in the microwave.
  • Cook food in the microwave only as long as necessary and use almost no cooking water.
  • Store the microwave in high traffic areas.

If you do not use a microwave:

  • Leftovers can be eaten cold. If you don’t need to warm up, you don’t need to. Every time we heat, regardless of method, we lose nutrients.
  • Try cooking on the stove, steaming or in a pan.
  • Also use the oven for baking and roasting.
  • Consider a toaster oven that uses less energy than a conventional oven. (Think of a solar oven).
  • Heat the water in the kettle.


Click here to see the sources of information referenced in this article.

Food and nutrition professionals can introduce methods to conserve natural resources and support environmental sustainability. 2007;107:1033-1043.

The influence of income on appliances in American households. 26. March 2009.

Microwave oven – Wikipedia.

O’Connor A. Really? 17. October 2006.

Howard B.C. Seven surprising facts and myths about microwaves. 14. July 2009. The Daily Green.

Song L & Thornalley PJ. Influence of storage, processing and cooking on the glucosinolate content of Brassica vegetables. Food Chem Toxicol 2007;45:216-224.

Cross GA & Fung DY. The influence of microwaves on the nutritional value of food. Crit Rev Food Sci Nutr 1982;16:355-381.

Home Book J. Microwave or toaster : Which kitchen appliance is the most environmentally friendly? 22. April 2009. Tree chipper.

Microwave ovens and their dangers. Canadian Centre for Occupational Health and Safety. 2. November 2004.

Sugarman E. Warning: Electricity in your area can be dangerous to your health. Simon and Schuster. 1992.

David D. Disconnected. Penguin Group USA Inc. 2010.

Levitt BB. Electromagnetic fields. Original harvest. 1995.

Netherlands Institute for Human Rights. Hertel against Switzerland. 1998. No. 87.

Taghavi N. and Yazdi I. Diet type and risk of oral cancer. Arch Iranian Med 2007;10:227-232.

Steneck NH. A discussion on the microwave. Massachusetts Institute of Technology. 1984.

Lopez-Berenguer C, et al. Effect of microwave cooking conditions on bioactive compounds in broccoli florets. J Agric Food Chem 2007;55:10001-10007.

Schmidt-Pokrzywniak A, et al. A case-control study: Professional cooking and the risk of uveal melanoma. BMC Ophthalmology 2010;10:26.

Ohlsson T & Bengtsson N. Microwave technology and food. Advances in food and nutrition research 2001;43:65-140.

Cross GA, et al. The influence of microwaves on the nutritional value of food. CRC Critical Reviews in Food Science and Nutrition 1982;16:355-381.

Driskell JA, et al. Influence of induction, conventional and microwave cooking on the sensory properties and carotenoid content of selected vegetables. Poster. J Am Diet Assoc 2006;Suppl 2:106:A-42.

Schardt D. Myths about the microwave oven. Nutrition Action health letter. 2005:10-12.

Cady M. In the microwave. The experience of life. January-February 2012.

Video – History of the microwave oven

What happens to food in the microwave and when idling

FDA – Microwave Radiation

Better eating, moving and living ©

The world of health and fitness can sometimes be confusing. But this is not necessarily the case.

You will learn the best nutrition, exercise and lifestyle strategies – unique and individual – for you.

Frequently Asked Questions

Does a microwave destroy nutrients in food?

No, microwaves do not destroy nutrients in food.

Why microwave is not good for health?

Microwaves are not good for health because they emit radiation.

Is microwave cooking safe for health?

Microwaves are safe for cooking food.

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