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Are Microwave Ovens Safe?

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Microwaving your food may not be as harmful as some health enthusiasts would lead you to believe.

are microwave ovens safe?
Microwave ovens are a convenient way to cook and reheat food. Maximkostenko/iStock/Thinkstock

Microwaves. These handy gadgets have been the source of much debate in the online health community, and it’s not hard to see why. The idea of “zapping,” “nuking,” or otherwise heating your food using microwave radiation can seem a little dubious.

In this article, I’ll take a look at the evidence behind some of the most common microwave concerns. Do microwaves leak radiation? Do microwaves destroy the nutrients in food? Do they denature proteins and make food toxic to our bodies? First, though, let’s start with the basics. How do they work?

How Do Microwave Ovens Work?

The aptly-named microwave oven uses microwave radiation to heat food. Electromagnetic (EM) radiation exists over a range of wavelengths, where shorter wavelengths (such as x-rays and gamma rays) have higher energy than longer wavelengths (such as radio waves). On the EM spectrum (pictured below), microwaves fall between radio and infrared waves.

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Each level of radiation has different effects on the molecules they interact with. Microwaves contain enough energy to induce molecular rotation, which is the lowest energy form of interaction, but they don’t have enough energy to induce molecular vibrations, electron excitation, or ionization. Microwaves have the greatest effect on water molecules, due to their polar structure, and these rapidly rotating water molecules transfer energy as heat to the other molecules in food.

Do Microwaves Leak Radiation?

One concern many people have about microwave ovens is the simple fact that they emit, well, microwaves. Hasn’t exposure to microwave radiation been linked to cancer and infertility? Evidence is mixed; most published research concludes that low-level microwave exposure doesn’t present a significant risk to human health. (1, 2, 3) Even if it did, this is only an issue if the microwaves inside the microwave somehow escape the microwave and encounter your body, which (as you’ll see below) is unlikely.

The FDA requires that microwaves emit no more than 5 mW/cm2 of radiation at a distance of 2 inches from the microwave. They also point out that microwave radiation dissipates rapidly as you move away from the source, so a measurement taken 20 inches from the microwave would be about 1/100 of the measurement taken at 2 inches. This is good news, because it means that to avoid radiation from your microwave, all you have to do is step away from it while your food is heating.

Are #microwaves as unhealthy as we are told?

The other good news is that in general, real microwave emissions seem to stay below the federally mandated maximum. A study published in 2013 on microwaves in Palestine found that the radiation leakage measured one meter from the microwave varied from 0.43 to 16.4 μW/cm2, with an average of 3.64 μW/cm2. (4) A 2001 survey of microwaves in Saudi Arabia concluded that with 95% probability, a microwave will be found to leak between 0.01 and 2.44 mW/cm2 at a distance of 5cm, and only one out of 106 microwaves surveyed was found to leak more than the FDA limit. (5)

For comparison’s sake, a 2013 study measured microwave radiation emitted by cell phones at a distance of 3.5cm from the phone, and found levels of 10 – 40 μW/cm2 during a call and 0.35 – 10.5 μW/cm2 on silent. (6) Based on these numbers, having a cell phone in your pocket on silent mode exposes you to roughly the same level of microwave radiation as standing one meter from your microwave while it’s heating food.

Honestly, just don’t press your face up against the door of the microwave while your food is cooking, and step a few feet away if you can. If you’re going to be concerned about exposure to microwave radiation, you’d probably be better off getting rid of your cellphone than your microwave oven. (But that’s a topic for a another day.)

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Do Microwaves Make Proteins Toxic?

Now, let’s talk about the effect of microwave heating on food. One oft-cited claim is that microwaves can “denature” proteins, making them toxic to the human body. First of all, I think there are some misconceptions about what exactly “denaturation” is. Contrary to how the word is often used, it doesn’t mean that a protein has ‘changed’ in some unspecified way to make it more toxic. When a protein is “denatured,” that specifically means it has unfolded and lost its three-dimensional shape, but all of the amino acids in the protein are still bonded together.

Heat in general denatures proteins, so cooking your food (using any heating method) will denature the proteins. Cooking can even be defined as heating something enough to denature the proteins. (7) Changes in pH also denature proteins. In fact, guess what one of the functions of stomach acid is? Denaturing the proteins you ingest! Proteins need to be unfolded (denatured) before digestive enzymes can cleave them into individual amino acids to be absorbed in your small intestine. “Denatured proteins” don’t sound so scary any more, do they?

Perhaps what people have in mind when they refer to “protein denaturation” is actually isomerization of amino acids. This is a completely different process, but it is a change that actually affects the nutritive value of proteins. Without getting too into the chemistry, amino acids can exist in two configurations, termed D- and L-, and isomerization is the process by which an amino acid switches from one configuration to the other. Our bodies almost exclusively use the L- form of amino acids, but pH changes and heat can cause amino acids in food to isomerize to the D- forms, which can’t be efficiently digested or utilized by our body. (8)

A few studies where large amounts of isolated D- amino acids are fed to rodents show potential harmful effects, but there’s no evidence that the levels of D- amino acids normally found in food are harmful. (9) Plus, many foods (such as raw dairy from ruminants and some fruits and vegetables) naturally contain low levels of D- amino acids.

In any case, there doesn’t appear to be a significant difference in levels of D- amino acids in foods cooked in the microwave compared with foods heated conventionally. One study conducted in 1989 found higher levels of D- amino acids in microwaved formula compared with other heating methods (10), but several more recent studies have found no difference. (11, 12, 13, 14, 15) Additionally, the general consensus seems to be that if more D- amino acids are formed, it is due primarily to over heating or uneven temperature distribution, rather than a specific effect of microwaves themselves.

Do Microwaves Destroy Nutrients?

As far as vitamins, minerals, antioxidants, and plant phenols, retention does not appear to depend on cooking method. Levels of nutrient retention were sometimes higher in microwaved food, and sometimes lower, depending on time, temperature, and amount of water used in the cooking process. (16, 17, 18, 19, 20)

In general, nutrients are lost from food during any type of cooking, and more nutrients are lost when the temperature is higher or the food is cooked for longer. Water soluble vitamins are readily leached into cooking liquid (no surprise there), so boiling food tends to result in greater nutrient losses than microwaving it with a small amount of water (unless you drink the water you boiled the food in, in which case you’d still be getting most of the nutrients).

As a final interesting data point, one study published in 1995 used a rat model to look at the overall effects of a microwaved diet in vivo. The diet consisted of meat, potatoes, vegetables, and some oil, cooked either in the microwave or conventionally, and was fed to rats for 13 weeks. To magnify any adverse effects of microwave cooking, the study authors added two additional experimental groups that received “abused” food, which had been reheated and cooled a couple times either conventionally or in the microwave. (21) At the end of 13 weeks, they found no adverse effects of microwave cooking on the rats.

Don’t Fear the Microwave!

In conclusion, microwaves aren’t as scary as some people make them out to be. Yes, they’re another source of microwave radiation in your home, but the levels are extremely low, and can be almost entirely avoided by simply stepping away while your food is heating. And compared with microwave radiation from other devices (particularly cell phones), radiation from your microwave oven is negligible.

Additionally, there’s no evidence that microwaves adversely affect the nutrient profile of foods. Because microwaves are a relatively new device, I prefer to think of them as “guilty until proven innocent” rather than the other way around, but given what we know about EM radiation and its effects on food molecules, there isn’t really a mechanism by which microwaves could destroy nutrients other than heat. And heat, of course, is an issue regardless of cooking method!

If you’re still skeptical of microwaves after reading this, by all means – use whatever cooking method makes you comfortable. I might be one of the few freaks in the world now that still doesn’t use a microwave, but I can’t say that it’s because of any safety concern or scientific concern. I’ve just never liked what they do to the texture of certain foods, and for whatever reason, I’ve never gotten into using one.

But if you enjoy the convenience of a microwave, don’t be afraid to use it – especially if being able to microwave your food makes the difference between heating up leftover Paleo chili or grabbing a Nutri-Grain bar for lunch!

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271 Comments

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  1. I no longer use one, either, but not due to fears about how it cooks – I researched the ovens when they first came out and came to the conclusion that if used thoughtfully, they shouldn’t pose any more risk than a pressure cooker. And the wave amplitude is easily and adequately stopped by the screens, so I went with it and at one point, a microwave and a toaster oven were my only cooking options.

    However, I do find that between the tendency to over cook since everything happens so fast (I seem to be the only one I know who lets food rest to finish cooking), the temptation to use preprocessed foods that are so easy and quick and available for the microwave, and just the additional space one would require in my already cramped kitchen, I am choosing not to even consider adding one back into my life. Instead, I am working on actually planning ahead to make sure I still can make meals relatively quickly and easily, but using minimally preprocessed foods. It’s honestly been a bigger adjustment than I’d anticipated, mentally – speaking, but I am finding after some months (I recently moved and so was able to go fully microwave free) that I am getting into the swing of it and am able to get better ingredients for my food budget and am naturally including more fruits and vegetables, if for no other reason than they are quicker to prepare than things like grains (especially since I have been trying to properly presoak/sprout them first! – the mostly non GMO grains)

    I use my slow cooker more and tend to combine a sort of quick saute and steam on the stove top as my primary cooking methods these days. I already own, but have yet to try a countertop halogen oven.

    Nice to see this topic handled rationally and with independent thinking;thank you.

  2. I would not assume that Federal safety standards are safe….they are always influenced more by money than by science….to equate the safety of microwave oven RF emissions to cell phone standards is doing no one any favor…. RF from cell phones and wifi is hazardous at levels way below govt. “safety” thresholds according to scientists not on the wireless industry’s payroll….

  3. Thank you for this article! A great investigation into how something “scientific” can be made to sound scary and harmful, but is not always the case. I so appreciate you delving into all aspects of proposed potential harms caused too. We don’t use our microwave very often, but as you said, if it’s the difference between getting a nutritional meal vs eating an undesirable (but easy) choice… than it can be a great option! As always, love your balanced perspective, thank you!

  4. Good information! I do not use a microwave because of the overheating of certain part of the food. Some parts will be dessicated and other left rather warm than hot. Then loss of nutrient availability and / or changes to the chemical nature of some foods may be altered and become hurtful.

  5. I stopped using my microwave on a regular basis when I was bedridden and had Leaky Gut 2 years ago. I was nutrient deficient and didn’t want to take the chance that my food would lose the nutrients that my body desperately needed.

    Well, I’m better now, and I haven’t touched my microwave – except to heat filtered water for my cleaning products – in a little over a year.

    I tend to trust the research you do, but I’ve adapted so well to heating my food in other ways that I’ll continue to skip the microwave. Just like you said, I don’t care for the texture that the microwave gives the food. It completely destroys the quality, and my food is too valuable and delicious to “destroy” it. 🙂

  6. We used a gaussmeter to determine the safe distance to stand from a microwave…it was in the other room!!

    • Yes, same here. The meters don’t lie and we found the same amount of leakage with a brand new microwave.

  7. I have an ‘infrawave’ oven that I use a lot for cooking. Does anyone have any idea how safe they are? Instruction book says it uses ‘specific wavelengths in the electromagnetic field’.

  8. When my last microwave died I didn’t replace it. Bought a tea kettle. I use a pressure cooker. Didn’t miss the microwave at all. In fact, I really disliked the noise the thing made. Life is better without it.

    • Our family bought our first and last microwave oven in 1995. If you notice, when reheating bakery items they become rubbery, also do steamed vegetables. I just used the good old fashioned skillet, pot, steamer, etc to reheat. I just believe it the holistic life. All around, technology is ever more increasingly exposing us to EMRs so this is my way of keeping it level.

  9. Interesting idea, but I still choose not to have a microwave. And I have heard that cell phones are causing deep concerns and have not been well studied. One study I heard about which showed cell phones were causing brain cancer in primates after just 30 days was pulled. Even if microwaves end up truly being safe, I don’t like what they do to the texture of food. But thank you for approaching this topic and getting us to try to open our minds. It is nice to know others who use microwaves may be justified in doing so. I had thought I heard years ago that infants received formula heated in a microwave were getting leukemia. I don’t know the source of that tidbit though. Thanks Chris.

  10. What about that old story of the blood tests, one group at fast food that was cooked fresh, and the other got reheated food (microwaved) and they tested the blood and found the microwave reheated fast food caused noticeable changes in blood molecules. I can’t find the original, but this one cites a few similar studies. http://www.naturalnews.com/030665_microwaved_food_cancer.html
    comments on this?

  11. Excellent, thank you! I look to you for thoughtful, reasoned articles with clickable citations. This helps ease my mind on microwaving (I use them primarily to gently re-heat certain foods and heat up my 96 year old father’s bean bag shoulder warming pads).

    Since you mentioned phone radiation, PLEASE PLEASE publish an article very soon on cell phone radiation. I’ve been stupid and accidently fallen asleep with mine many times, walk around with mine 12-14 hours a day, and only recently realized just how dumb I’ve been. I need to figure out how to minimize exposure and immediately do smart things like get a REAL alarm clock and keep it on the other side of the room at night. So I’m very anxious to read an article by you about cell phone radiation risks, safety precautions and maybe even what to do if you think you’ve over-exposed yourself…

    Thank you again!

  12. The cellphone? Yeah, it’s time for that conversation. The industry has known all along about the dangers.

  13. I’m sending this article to the Food Babe, who thinks microwaves are mini nuclear reactors.

    One more note on microwaves: I’ve been heating up wet cat food with probiotics in it, and the microwave neither destroys the food NOR the probiotics.

    • how do you know the probiotics aren’t destroyed? did you test them for viabiltiy after you nuked them??

    • I have had frequent bouts of many very small ants who sometimes wind up inside my microwave.

      When they were inside and I was heating water for tea, they were still moving when it finished, about 60 seconds later on.

      Looks like Chris has some very good points.

  14. Great article Chris! Keep um’ coming. I really enjoy your analytical approach to these types of debated topics.

  15. I am not convinced by this article. I have seen plenty of research that indicates the opposite. I have no intention of using a microwave and continue to counsel my patients likewise. Some of the points in the comments are well taken, specifically about containers and which foods are used in the first place. Not to mention, that food cooked in the microwave tastes and looks terrible. Stovetop and/or oven is the way to go in my opinion.

  16. Good article! I always wondered about nutrient loss and thought the opposite of what you said. Glad you cleared that up. Thanks