Are Microwave Ovens Safe for Our Health | Chris Kresser
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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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Image Source.

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.)

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!

271 Comments

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  1. It’s basically an inside out Faraday cage. I unplugged it and stuck my laptop in there when I heard we were getting a solar flare. Just in case. It is totally safe. It’s not going to “leak radiation” out and give you cancer. LOL people are paranoid.

  2. Is it true or hype that the nazi’s invented microwaves but then scrapped them because of the effects that they had on the soldiers. I have heard this story similarly with Russians substituted for Nazi’s. Still this story is a shocker to my puritanic long held health values.

    • I know that back in the 70’s microwaves were banned in the USSR because of their negative effects on health.

    • There is absolutely no evidence whatsoever that the Soviets banned microwave ovens in 1976 or any other time, there certainly wasn’t a law passed. Various debunkers have asked Russian lawyers to find the law or the law repealing it. Every single quote on the internet has the same source – ultimately Bill Kopp’s article that was incorporated in Wayne and Newell’s articles then quaoted in Mercola.com.

      Likewise, there is no evidence whatsoever that the Nazis invented MW ovens and lots against it, not least of which is that microwaves are very useful for radar yet the Germans never produced centimetric radar (the British did as they had developed the cavity magnetron, but they did not develop the MW oven).

      However what better conspiracy that to say that one evil empire invented a process that another evil empire had to ban yet we do nothing. One couldn’t fudge it any better!!

  3. A simple test you can use is to heat water in a microwave oven, then let it cool to room temperature. Get two plants that are just alike and feed one water from your tap and the other one from the prior microwave heated water. The one that is fed the microwave waved water WILL DIE!

    • That is ridiculous. If you really want to run this as an experiment, you need far more than one plant in each watering group. If you only have two plants, one of them could die from just about anything. You need a significant number of subjects to show any kind of association. Then someone else needs to replicate your experiment. After that, you may say you have some compelling evidence. Reminds me of the cute child in the video who grew sweet potatoes (or something). Talk about bad science.

      • Plus you’d need a group that is getting water that had been heated conventionally and then cooled, just to control the other variables. Otherwise you don’t know if heating and cooling the water is the problem (if there is one) or if it was the microwave.

    • Have you done this experiment or merely read it on the internet?

      My son did this for his high school science project and found no difference. Subsequently I became a judge at the science fair and have seen several repeats of the experiment all with the same results, i.e. no significant difference.

      Over several hundred plants and half a dozen different student studies and the results are consistently the same. No significant difference.

      I wonder where your results come from and please don’t quote the EUTimes / Arielle Renolds’ daughter or somebody’s granddaughter. That was found to be faked years ago.

  4. Great article,

    I would like to see you weigh in on other forms of electronic radiation, such as Bluetooth devices, cell phones, wireless internet etc…

    • Don’t forget the effect of ordinary, every-day electromagnetic radiation exposure from electricity — all your appliances, your alarm clock, vacuum cleaner, blender, toaster, lamps, everything that runs on household AC current. Get the electricity away from your bed.

    • Yes…please Chris follow up with article re wi fi in the home, use of cell phones, living near cell towers etc.

  5. I think one of the big questions is what container you are microwaving in- if it is plastic there is probably the risk of chemicals leaching into the food from the microwave heating- I wonder if there are any studies on that?

    If reheating food that was stored in a plastic container I try to put in a regular bowl or plate before microwaving.

    I also agree with the commenter above- most microwaveable ready foods are complete crap and will probably cause more harm than the radiation leaking out of the microwave.

    • Plastic is actually inert. The danger lies in the chemicals used to join the c ‘ s h ‘ s etc. the residues that remain behind despite rinsing processes after manufacturing. Cooking in plastic is very bad. Also, storing liquids in plastic–like water, milk, etc–very bad.

  6. I’ve heard that microwaving food destroys the “life-force” of foods, which isn’t destroyed by conventional heating methods. Do you know of any studies in regard to this?

    • I’m not sure what people mean when they refer to the “life force” of a food, so it’s hard to address this. However, if they are talking about protein structure, I did mention this in the article. If they are talking about enzymes, then yes, microwaving would destroy some of the enzymes—but so do all forms of cooking/heating above a certain temperature. And despite the claims of raw food advocates, cooking food often improves our ability to absorb and process it. Anthropologists believe that consuming cooked food was a significant factor in our evolution.

    • I think killing food also destroys the “life-force” of it. From now on why don’t you try eating nothing but living animals. You can’t eat any more plants because they are dead too. Well i suppose you could still eat potted plants with the soil, roots and all to keep it alive as long as possible.

  7. I always re-heat my leftovers in bain-marie or in a standard oven. Very rarely I use the microwave and it is uniquely at workplace, where I just don’t have the choice. Even in these cases I keep the power to low and heat until just warm, not at maximum power to steaming so I don’t have to wait until it cools down.

    Apart this, I find the microwave extremely useful to heat water to prepare a tea (no nutrients to destroy in plain water), or to sterilize a cloth before straining yoghurt 😉

    My 2 cents.

    • I believe this is the best part of this. My wife’s parents want their food steaming hot and so my wife tends to want to do the same with the microwave. It has been my opinion for a long time that heat is the enemy. I reheat until it is warm. It makes absolutely no sense to reheat the food where you have to let it cool or burn your mouth.

  8. Microwaves are supposed to be good for sterilizing cleaning cloths. Correct me if this is not the case…

    • Its actually the temperature reached that causes sterilization. This can be accomplished through any means of heat.

      • Thank you! I couldn’t remember the right term (I discovered a TIA can muck with things like language recall 🙁 )

        • Don’t worry about it Elissa. There are plenty of people out there saying that microwaves sterilize cleaning cloths and sponges, who don’t have your excuse for using the wrong word. I’ve probably said it myself a time or two.

  9. Some years ago I met a woman who said that when she ate microwaved food her white blood cell count went down … Anyone else come across that?

  10. After receiving emails showing pictures of how microwaved water “killed” plants, I decided to conduct my own experiment. 15 students were each given 2 lots of seedlings of the same species and age. One lot was watered with water that had been boiled in a kettle and cooled; the other lot with water boiled in a microwave and cooled. After several weeks, there was no appreciable difference in height or colour in the 2 lots of seedlings for all but one of the students, where the seedlings watered with microwaved water was slightly taller. After seeing these results, I decided to continue using my microwave.

  11. Thank you Chris,
    So informative. I have been wondering about the truth on MWAVES for ages. This helps clarify the info so well. Now I can make an informed choice when re heating for my loved ones & our pets.

  12. From a Weston Price article:
    ‘According to a letter published in The Lancet, the common practice of microwaving converts l-proline to d-proline. They write, “The conversion of trans to cis forms could be hazardous because when cis-amino acids are incorporated into peptides and proteins instead of their trans isomers, this can lead to structural, functional and immunological changes.” They further note that “d-proline is neurotoxic and we have reported nephrotoxic and heptatotoxic effects of this compound.” In other words, the gelatin in homemade broth confers wonderous benefits, but if you heat it in the microwave, it becomes toxic to the liver, kidneys and nervous system.’
    That would be this study:
    LUBEC, G. ET AL. (1989): AMINOACID ISOMERISATION AND MICROWAVE EXPOSURE. – THE LANCET, 9: 1392-93
    Maybe it is similar to comparing manufactured msg to naturally occurring msg. A lot of people react to added msg but not msg in say, tomatoes. Same with cysteine and some others. I react to broth anyway – it has an excitotoxic effect on my brain.
    I have always gotten a gut ache from food cooked in a microwave. They say that microwaved food can affect people for months after eating it. I used to get MORA tested, and during that time, the one time I ate microwaved food it showed up weeks later in testing as causing stress on my body. No, I did not mention to the person doing the testing that I had eaten any.
    A study that found that microwaves denature food more than thermally heating:
    http://www.ncbi.nlm.nih.gov/pubmed/18240290
    A friend had a microwave oven that I could feel metres away – it was a bit old though so maybe the door didn’t close as well as it should. I’ve electrical hypersensitivity and react worst to mobile (cell phone) radiation. Microwave transmitters have a spacing out, dumbing down effect on me too.
    What about the Swiss study that found hemoglobin etc was affected by eating microwaved food? The study is in here:
    http://www.naturalscience.org/wp-content/uploads/2015/01/wfns_special-report_microwave_02-02_english.pdf

    • I’m confused by a couple of things that you posted. I’m not sure what “conversion of trans to cis forms” and “converting “l-proline to d-proline” have to do with each other. Maybe if I read the article it would make more sense, but I can’t find it, and you didn’t link to it.

      I’m not sure I get your point about microwaving denaturing food more than thermal heating. You seem to consider this a bad thing. However, as Chris’ article says, proteins have to be denatured our digestive enzymes can do their thing. Seems to me that more denaturing would be a good thing.

  13. I’m with you Chris……………I must be the other person in the world not using a microwave. I have managed really well without one for years and really don’t see the need for yet another gadget.

    • i haven’t used a microwave since 2003. I don’t like what they do to the food. I also read somewhere once that they were designed by the Wermacht during the Second World War for use in panzer divisions during the assault upon Russia but they were deemed as to be of no use as they destroyed the nutrients in the food. Cannot remember my source but it may or may not be true.

  14. Fantastic article! I like that you emphasise that if the alternative is junk food or calorie dense nutrient deficient substitute microwaved meat and vegies is a brilliant alternative.

  15. In the earliest days of microwave ovens, interlock switches were often not used in the commercial microwave ovens used in restaurants. Frequently, the doors would be removed from these ovens and they would be operated continuously allowing cooks to place and remove food quickly from within the ovens.. Of course, the cooks’ hands would be exposed to the full microwave field for a few seconds. In general, this did little harm other than raise the internal temperature of the hands a degree or two. However, when the ovens were mounted close to eye level, the cooks often developed cataracts. This was due to the fact that the cornea of the eyes has a very limited ability to dissipate excess heat (unlike the hands which have good blood circulation).

    By the way, most wireless computer routers share the same frequency bands as microwave ovens.

  16. So when I heat liquid to dissolve gelatin, I’m isomerizing the L-amino acids in the gelatin to D-amino acids, and cannot assimilate these well, possibly causing harm. So I probably shouldn’t use gelatin in heated liquids.

  17. Is this sentence correct? “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 L- forms, which can’t be efficiently digested or utilized by our body.” I think you mean food can be isomerized into the D-form.

    And thank you for debunking the microwave fears. My friends routinely give me the silliest arguments for why they don’t use microwaves. This is a well thought out response I can send to them.

  18. If the labels on my microwave oven are representative of what most people use theirs for – pizza, chicken nuggets, “hand-held snacks”, “frozen kid’s meals” (whatever these might be), and hot dogs – I would say it’s the type of food that is more likely to be dangerous than the action of using the microwave oven.

  19. When reheating frozen leftovers, is it better to err on the side of overheating (to ensure the temperature goes above 165 °F) or on the side of underheating (to miminize isomerization and/or amine formation)?

  20. One factor that you may not have taken into account is the possibility that older microwaves’ doors stop closing as well and begin to release much higher EMF radiation than when they were new. Dr. Jack Kruse in several of his podcasts (such as with Beverly Meyer, titled “Jack Kruse on EMF’s a few years back) says that he has tested older microwaves and has noticed that after several months the amount of radiation released increases dramatically. I have no idea if any studies have been done to back up his claims but if it is, in fact, true that microwaves release dangerous amounts of radiation after several months, because industry doesn’t care to make the doors durable (after all, all the studies were probably done on new microwave ovens), then many people could be at risk. But again, I’m open to being corrected as I realize I have no evidence to back up Dr. Jack Kruse’s claim.

    • My dad purchase one of the first microwaves from Litton Industries years and years ago. About a year later purchased a Gauss meter (which I wish I had today). Yes, the doors leak. He took the door apart and re-insulated it, and later purchased a new microwave. Again, took door apart and re-insulated it. Seems every 2 or 3 years, he would purchase a new unit. This is precisely why I do not own one of these – it is invisible and you have no idea what’s going on unless you purchase a meter and test for yourself.

      • Uh oh. I still have the old Litton microwave my dad bought when they first came out. Yes, I have a microwave from 1971. I don’t use it very often as I prefer to heat things on the stove, etc., but about once every 6 months or so I plug it in and use it for something – standing away from it when it’s in use.

        Do you know how your dad re-insulated the door?

    • That’s also why they recommend not being close to one with a pacemaker! But honestly, we are surrounded by all sorts of radiation, natural and man made, and being close to or in constant exposure to any of them is definitely affecting us, even on a cellular level. IIRC, our best guess as to why life arose from the primordial ooze is due to the effects of exposure to certain frequencies of radiation – so it is a fact of our form that we’re susceptible. With any source of radiated energy, a little distance is always a good idea. And eating well is, in my opinion and understanding, one of the best ways to counter the effects. However, as with anything else to which we are over-exposed, there are some folks whose bodies simply cannot handle it anymore and so it is important to be aware of how one feels around such devices and situations and adjust accordingly.

      I am one who cannot handle all the concentrated chemicals and have had to make major adjustments for that, so I totally get the concerns, but also caution against being overly worried as I strongly suspect more folks suffer from the stresses caused by being afraid of things than by the actual effects, if that makes sense.

      • Amen Elissa! There’s too much stressing over little things which certainly isn’t healthy. Let’s not sweat the small stuff.

        • Ditto, Laurel and Elissa! I’m convinced that my body’s biggest enemy is stress/worry/strife/anxiety, and less so the evil toxins and exposures lurking everywhere.

          (Remember the longevity study with the WWI (or was it WWII) soldiers who smoked and were anxiety-free vs the ones who didn’t smoke and were high anxiety and which group lived longer?…you can just guess! Of course, I’m ardently anti-smoking, and a healthy life is as important than a long one it, but there’s still a lesson to be learned there!)

          “Don’t worry, be happy” is a simple, but also deeply meaningful, song and mantra!

      • Extremely well put, Elissa! Thank you. I am in that same boat, with both the sensitivities as well as trying not to fear too much because I do suspect that is the majority of potential harm to health. It does seem the best advice to counteract is to be moderately well informed, moderately cautious, eat as clean and healthy as possible, and not worry too much.

      • Elissa — I agree with you. We should certainly inform ourselves, but there is a point where it becomes harmful to stress so much about minor things. It’s telling that the new eating disorder term “orthorexia” has been coined (witness many of the commenters on this article).

        Do the best you can, and then enjoy your life. I suspect that no dying person has ever said, “I wish I spent more time on the internet reading health articles”!

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