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.
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)
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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I use those plug in the wall devices and wristbands that are sold, purported to block harmful EMF’s (from the variety of sources we’ve all cited).
Are those at all effective?…Any studies on them?
I don’t own a microwave because I do not like the ever-present heat/cold spots in my food. I like my electric stove because I can put on a pan, on the low setting, and whatever is inside will be perfectly ready in 15 to 20 minutes, never too hot or overcooked. For vegetables, there simply is no better way to prepare them, than by steaming, which releases so much flavor, I never have to use condiments, which are all nothing more than empty calories that our bodies are better off without. Perhaps my greatest aversion to microwaving my food is the necessity for plastics, which I do not even allow in my home anymore.
It is not a necessity for plastic when microwaving – glass a ceramics work just fine. You can use paper plates, napkins, etc. too.
That should be “There is not a necessity…”
I am so grateful for this article! Thank you Chris! I have been struggling with avoiding the microwave due to fearing its effects on food but I so miss the convenience of reheating items. Now I am going to microwave without fear. Thanks again.
Wondering about what things are used to cook in inside a microwave. IE if we use glass that is leaded, does the led go into the food? If we use plastic microwavable materials, do PCBs find their way into the food we eat? What are the dangers here?
You are not likely to find PCBs (polychlorinated biphenyls) in your plastic containers to begin with. But it’s best not to heat food in ANY plastic containers by ANY means. Use glass, ceramic, paper, etc.
True. You will find PCBs in some older transformers and some industrial equipment, but not in plastics.
Miri, I believe you meant BPAa (bisphenol A) which are found in some plastics.
Thanks for this perspective on microwaves. Do you have any research on induction cooktops which are both seen by some as a great eco option and others who demonize them for their electromagnetic properties?
I have never owned a microwave in my entire life, haven’t used one for more than 7 years, and will likely never buy one. Not even after I read this article, not that I don’t agree with what it says, just found it unnecessary.
Thanks. Relieves my anxiety about this!
Thank you for this. A couple of comments to add:
1) It’s never a good idea to heat foods in plastic containers by any cooking method. It’s not because of microwave radiation, specifically, but because heat from any source can cause chemicals in plastics to leach out. This could include blending your hot “bulletproof” coffee in a plastic Vitamix, for example. (Disclosure: I do have a petition on Change.org asking Vitamix to offer a plastic-free alternative.)
2) I’m more concerned about the toxic indoor air pollution from my gas stove than the tiny bit of radiation from my microwave.
3) Microwave ovens are much more energy efficient than conventional stoves since they cook so quickly and only heat the actual food, not the surrounding air. So we’re saving fossil fuels.
4) You can save resources and energy further by acquiring a “new” one second hand. When our old one died, we replaced it for $10 from someone on Craigslist.
5) All that said, I don’t like the texture of many foods cooked in the microwave, so, like others, I only use it for quick reheating.
I think you are quite right in being concerned about your gas stove. We moved from a home with gas to one with halogen heating elements. Immediately saw a reduction in colds and respiratory symptoms family wide. For that reason even though we are pretty serious about cooking we will not go back to gas.
(The kitchen is also much freer of the oily deposit gas leaves on surfaces–even with good venting.)
Chris, can you point us to any long-term (i.e., 20 to 30 years) studies looking specifically at the microwave and carcinogen factor? Microwaves have been out long enough that there should be some longer-term data available. For instance, is there any association between cancer and daily microwave use after 5, 10, 15 years? While short-term studies are valuable regarding nutrient density of microwaved foods, it’s the long-term habits — using a microwave to heat and cook food every single day — that can have far-reaching health consequences. Thanks!
I wouldn’t necessarily trust cancer research even if it’s available. We all know how skewed “science based medicine” can be. Chris has written about this. Industry profits rule over health.
The problem is that any research that would show higher disease rates in microwave users would be simply an epidemiological study. This means that all the “health nuts” who stayed away from microwaves would have better health outcomes “proving” that microwaving food is harmful. The problem is that this is useless data — all it shows is that people that believed microwaves were harmful were the same people that believed getting plenty of exercise, eating right, avoiding drugs and living a low stress life is healthy. How can one possibly run a double blind placebo test for microwaved foods over 20-30 years (or where would the funds come from?).
+1
I’d guess that after controlling for the type of food people are heating in the microwave (ready-made frozen franken-food?), container type (plastic leaching), and the various healthy user effects you mentioned, any association between microwaves and ill health would disappear. Many older cooking methods are actually demonstratively worse for our health (typically respiratory).
Well reading all these comments, I guess I’m a minority here, using the microwave a LOT. Not to cook or defrost meat or anything bready (yes, my non-paleo hub eats gluten), but regularly for cooking veggies, buckwheat, or a quick reheat of something like that or liquid. Sometimes to temper chocolate or melt butter. It’s partly because it’s faster and more convenient than conventional and also laziness because clean-up is so much easier.
So I guess I’m going to glow in the dark some day. We are also being radiated every day in the sunshine and wind stream of Japan and more so if we eat pacific seafood, which I do too. I’m not saying that I don’t care about radiation levels, I very much do, but I think Chris makes an excellent point that our exposure to tech gadgets like cell phones, wireless phones, etc and the unescapable polluted natural environment are even more concerning.
But based on Chris’ excellent article, I am going to make a point of staying farther away from the Mwave while it’s running. Thank you Chris!
Susan, perhaps you were only joking, but you seem to be confusing non-ionizing radio-frequency (microwave) radiation with ionizing radiation (radioactivity, such as from uranium and the like.) They are two completely different things.
A microwave oven does not make food radioactive. Nor do microwaves cause chemical changes to food, other than as a by-product of heating, which may occur during any form of cooking.
I am in that minority too. I cook lots of veggies in our microwave. I DO thaw meat. I boil water. Etc. I don’t cook meat except for bacon.
People often place paper and plastics into the microwave: paper towels, paper plates, plastic wrapping/packages, plastic forks, coffee Styrofoam cups, etc. Chemicals and BPA are leached.
I’ve read many accounts of carcinogens forming from microwaving foods. There is plenty of Russian and German research of microwave cooking back in the old days. Have you seen those studies? I think I’d trust old studies more than new ones.
Cooking on the stove, in the oven, or over a fire also produces carcinogens. It’s likely that whichever method causes the least browning has the least carcinogens.
You’re not the only freak left to not use a microwave, Chris. I have refused to have one in my house or eat/drink anything prepared in one EVER. Yes, friends do think i’m a nut, but for me personally and MY health, some things are just intuitively wrong.
I agree. It’s funny, I recently said that even if my most respected health experts like Chris Kresser say it’s ok to use a microwave, I’m still not going to. That’s just me. Why risk it? When I got rid of our microwave my family hardly complained at all. They trust my judgement of erring on the safe side.
Chris – Thanks again for cutting through the bunk and hyperbole that is too rampant on the web, and especially amongst health seekers.
This is THE best, most comp. article on its use I’ve seen.
ONE MORE QUESTION, CHRIS: Does the age of the microwave affect the amount of radiation exposure…Has leakage been tested to see if it increases over time/use of the appliance??
Thanks! Galia
The microwaves are stopped by the metal that the oven is constructed from (the wavelength is such that it does not penetrate the holes in the metal used for the window). So I can’t see how it could ever change over time (it’s not like ionising radiation, so it doesn’t make anything radioactive).
Very good article – thanks, Chris. I appreciate your comments and cited research on the amount of radiation emitted by the microwaves and how they affect nutrients in foods.
What about the effect of microwaving foods in plastic containers, which is a common practice? Can this be a possible and dangerous source of toxins over the conventional cooking methods?
13 weeks? That’s only three months. Isn’t that the same test they did on GMOs?
But 13 months is about 1/3 to 1/2 of a domestic rat’s life span (based on a quick Google search). Rats live about 2-3 years, give or take, according to most sites. A UK study found the average to be 21.6 months. So it’s a bit different than doing a 13 month study on humans.
What a great point!!!!
for the TRUTH – http://tv.greenmedinfo.com/microwaves-damage-food/
Thank you for posting this. While I think that it is great that Chris clears up some misconceptions and that it is always better to be better educated on issues, my gut feeling is more inline with the video you posted. Energetically, cooking your food in the microwave seems lower vibrational and like the man said, violent, so why would someone want to put this energy into their food?
Chris,
I like Francis Pottenger’s study on cats and the effects of cooked food on the skeletal development of their offspring.
What do you think?
-Larry
Electromagnetic radiation aside, the effects of heating by microwaves on water molecules are much different than that of conventional heat transfer (ovens, convection or otherwise, stove top, etc.) The temperatures that can be achieved when heating water as steam are much higher than with liquid. Superheated steam can reach temperatures of up to 910 degrees F. Any steam from evaporated water trapped within the food heated in a microwave can reach much higher temperatures than normal cooking in an oven or in a pot on the stove. The chemical alterations of hydrocarbons and proteins at elevated temperatures are a health issue. Something to consider over exposure to microwave energy. The radiation leakage is still a significant issue but knowing the physics and electrical engineering behind the device, I would lean toward the effects of superheated steam over some of the other issues.
You are not likely to find PCBs (polychlorinated biphenyls) in your plastic containers to begin with. But it’s best not to heat food in ANY plastic containers by ANY means. Use glass, ceramic, paper, etc.
Superheated steam can get hotter than that, but only under high pressure. At atmospheric pressure, water boils at 212F (with very slight variations based on elevation above sea level). If you want to superheat it, you have to contain it under pressure. Your microwave is not a pressure vessel.
The notion that the microwaves do no leak out of the microwave is just that, a notion. I got a radiation detector to measure the safety of my cell phone. I was shocked when it picked up radiation from the microwave while sitting on the kitchen table. When I called the mfg they sent out a technician who informed me that contrary to what people think they don’t even have seals on the doors anymore. Built in microwaves have no side panels. They leak radiation all around the unit. You can rely on the FDA or you can step far away from your microwave, like the next room.
It’s not a notion, it has been studied extensively in the scientific literature. I reported on those studies here.
I believed in that notion until a fluke forced me to check it out for my self. I believed that manufacturers would not manufacture something that leaked. I don’t know what to tell you about your research, but if you look at a new microwave there is no mesh in the door and no magnetic seal around the door. I was told by the technician that my microwave was not defective, and that all new microwaves are manufactured in the same manner. I purchased better meters and got the same results. I was told that the FDA does not recognize it to be harmful so precautions are no longer taken during manufacturing. You have provided research, but have you actually checked your own microwave for yourself. In some kitchens it is not possible to step away from its while its cooking.
One of the studies you have quoted, “The Impact of Cell Phone, Laptop Computer, and Microwave Oven Usage on Male Fertility” says that it is still controversial and goes not to state, “Current literature on EMW radiation effects on male reproductive health remains controversial with mixed and inconclusive data… Given the safety of EMWs remains undefined, further studies are necessary to clarify this potentially important public health issue and possible cause of unexplained male infertility.”
My chemistry professor told us following story: As an intern he was working in nuclear reactor. They have monitors on the clothes and his came high and they did not know why, because others around him were fine. So they followed him around. He went outside during lunch break—aka on the sun–which triggered alert. Radiation is everywhere. I would like to ask about the molecules of water that gets excited which produces heat. Since we are made out of the water mostly–this can affect our system in long run, but that would have to be very long study and someone in cafeteria who heats up food for many people.:)