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Serving up health and fitness insights (daily, of course) with a side of irreverence.
18 Mar

Are Microwave Ovens Safe?

MicrowaveTo Nuke or Not to Nuke?

The verb itself suggests the unleashing of atomic destruction, but we wondered, “Is there a grain of truth behind the slang?” What’s the real story behind these boxes of convenience sitting in so many of our kitchens? Are microwaves a benign bastion of modern handiness or, as some claim, a sinister contributor to our physiological (at least nutritional) undoing?

It’s likely that we find ourselves in a variety of camps on this issue. Some of us swear them off. Others unapologetically swear by them to get through the normal course of a busy day. And then there are those of us in the dithering middle who routinely stare at each plate of leftovers or bowl of frozen vegetables, sometimes reaching for the pots and pans and other times giving into convenience but always questioning whether we’re paying for it.

Should we be plagued by these pangs of conscience? Are we emitting dangerous radiation into our homes or killing off the nutritional value of our unsuspecting food? Are we making a mountain out of a molehill? What should we believe? Is there enough evidence to really tell either way?

We definitely know this much. Grok didn’t have a microwave. But, then again, he didn’t have a jet shower, Bose stereo system, or Hammacher Schlemmer thumper massager. (Trade-offs, you know…) As much as we love Grok and think his era has been unduly disparaged, we aren’t arguing that he had the best life possible or that anything he didn’t have isn’t worth having. Nonetheless, while it’s a naturalistic fallacy to assume that everything post-Paleo is an abomination, it’s both fair and reasonable to question the safety of today’s customary appliances.

Here’s what we found. First, to the question of transforming your home into a radiation zone… There is, not surprisingly, disagreement about this point. However, occasional home use of a fully functional microwave appliance is generally considered safe. Microwaves do, make no mistake, emit radiation, and the FDA has established what it considers “safe” levels for microwaves: over the machine’s “lifetime” the allowable level is “5 milliwatts of microwave radiation per square centimeter…approximately 2 inches from the oven surface.” Guidelines from the International Radiation Protection Association (IRPA) suggest overall radiation limits of 1 milliwatt per square centimeter “averaged over 6 minutes (0.1 h) period.” Unless you’re using your microwave on a perpetual basis, there’s little reason to worry.) Because the radiation diminishes quickly over distance, standing further away from the microwave during operation cuts your exposure even more significantly. (That instinct to not press your face against the glass door while your lunch was cooking turns out to be right after all…) Additionally, the FDA requires two interlock systems that effectively offer backup security as well as a monitoring system that shuts the microwave down if one of the systems isn’t working or if the door is opened during operation. Common sense adds that you might want to make sure the microwave seal isn’t compromised by built up tomato sauce or other grime. (Hmmm…anyone?) And, of course, it’s a good idea to replace an old, dilapidated microwave even if it’s a great conversation piece. Safety versus vintage flare…

And now for the more common question. What about the nutrients? (We should mention quickly that microwaving of food isn’t the same as food irradiation, which involves a higher level of energy and is considered much more damaging in terms of “complex chemical changes … in food components.”) But how do nutrients fare behind the closed, latched, double interlock system door? Well, it varies. As we’ve reported in the past, cooking of any kind can sometimes reduce the nutritional value of food and occasionally enhance it. Slow and low are typically the way to go with cooking, as we’ve said. A pretty much universal concept for our friends, fruits and veggies: steaming or cooking/microwaving with small bits of water trumps boiling or deep frying. When it comes to microwaving itself, studies suggest some mixed reviews for individual vegetables or nutrients but indicate, overall, that microwaving generally preserves nutrient levels.  One study using Brassica vegetables found that microwaving resulted in comparable nutrient (glucosinolates, a possible cancer preventative compound) loss when compared to steaming or stir frying.  (Actually, shredding the vegetable ahead of time had more impact on nutritional value than the cooking method.) However, another study using broccoli suggests that antioxidants can be significantly depleted.  (Antioxidants, particularly water soluble vitamins, appear to be most at risk while minerals tend to be generally preserved in microwave preparation.) Yet another study review showed that microwaving with low power settings offered “equal or better retention of nutrients … as compared with conventional, reheated foods for thiamin, riboflavin, pyridoxine, folacin, and ascorbic acid.” University of Illinois research also showed that microwave blanching (brief exposure to high heat used for pre-freezing preparation to lengthen storage ability of frozen produce) was as or more successful in retaining nutritional value than conventional blanching methods. (Nonetheless, blanching does diminish nutrient levels.)

But how could microwaving actually preserve more nutrients in many cases? Not only do we generally use less liquid when cooking in the microwave, cooking times are typically shorter than those for conventional cooking. (As a side note, new ceramic cookware designed for microwave use shows promise to cut cook times further still, which can mean even greater nutrient preservation.)

Our best advice: nuke wisely. If the convenience of a microwave keeps you committed to PB eating, use it as you need to. (We’re all for leftovers, freezing fresh produce to save money, etc.) Nonetheless, thinking outside the micro box is likely a good idea as well. Invest in some small pans for single servings or small cooking jobs. (If it takes up less space in the dishwasher/sink, it seems like less of a chore.) And, of course, avoid heating (and especially reheating) whenever you can to retain the most nutrition. Heat only the ingredients you must to make a dish palatable, and keep water use, time and temp (power level) as low as possible. (Bonus: it helps you avoid those nasty steam burns from handling overheated dishes.)

Have your own reasons for yea or nay on nuking? Let us know what you think and any tricks you’ve found useful to avoid or minimize microwaving.

limonada Flickr Photo (CC)

Further Reading:

Should I Stop Eating Flax Seed?

8 Ways to Reduce Your Chemical Load

What’s Wrong with Juicing?

You want comments? We got comments:

Imagine you’re George Clooney. Take a moment to admire your grooming and wit. Okay, now imagine someone walks up to you and asks, “What’s your name?” You say, “I’m George Clooney.” Or maybe you say, “I’m the Clooninator!” You don’t say “I’m George of George Clooney Sells Movies Blog” and you certainly don’t say, “I’m Clooney Weight Loss Plan”. So while spam is technically meat, it ain’t anywhere near Primal. Please nickname yourself something your friends would call you.

  1. Hey anon – don’t you think your little asinine crusade is ridiculous? Stop your hate mongering. Using science to explain why a microwave is not harmful is exactly that – science. Whether you agree with it or not does not give you the excuse to be a jerk. If you had any valid points, they are drowned out by your vitriolic crap. Have a little respect for other people’s opinions. You seriously sound like you think someone you know what killed by a microwave. What did it do – grow legs and arms and slaughter your baby?

    This website is populated by respectful people who can disagree without resorting to disrespect or insults. Your manner of communication is distasteful to more than just the commenter you are insulting – it is a problem for a reader as well. If you have a point to make, do it like an adult. For all I know, you have something valid to say but it can’t be heard behind everything else you have to “say”.

    lady_daraine wrote on December 31st, 2009
  2. The quick answer is no. Microwaving food isn’t safe, any extra-natural radiation isn’t safe. Genetically modified fruits and vegetables, and sugar (Aspartame, etc) are also not safe, the broken DNA has a negative effect. Any argument in favor of microwaving food and genetically modifying it is just someone lying to themselves and trying to rationalize their lifestyle. I eat microwaved foods sometimes, but make sure I get proper nutrition from other sources. For the record, one of the key players in getting the FDA to finally approve aspartame (after years of rejection) left the FDA and worked for the company producing the product. Peace.

    Rob wrote on January 6th, 2010
  3. Wow, no more zoodles for me.. 😐
    I don’t usually eat that much microwaved food anyways and i hope to keep it that way now..

    Josh wrote on January 9th, 2010
  4. I’m another non-microwave-user.
    I have a glass bowl Turbo oven, (which I love) & can use it for reheating most types of leftovers.
    I also remember reading Mercola said he sometimes leaves leftovers on the bench at room temp. to ‘warm up’ for lunch.

    Anita wrote on February 11th, 2010
    • Wow. Mercola. A brilliant source of reputable knowledge if there ever was one. Not.

      This thread is depressing. Lots of people believing that the evil microwave will somehow change your food into poison with zero evidence to support that.

      Jake wrote on January 30th, 2011
  5. You get more cancer causing radiation from the radioactive decay of Carbon 14, Potassium 40 and other naturally occurring isotopes that are in you body than you can ever get from a microwave oven. Thats right you are radioactive. And so was Grok.

    Ben wrote on February 22nd, 2010
  6. Microwave ovens heat by exciting water and other polar molecules (like fats). But the intensity of the EM waves is contained, that screen on the door is 10 times smaller than the microwave (which has a wavelength of about 12 cm. The screen acts like an antenna. The microwaves cause a current which is then sent to the ground prong on the plug. Just like the radio waves make a current in your car antenna and it goes to your speakers to make sound.

    Lastly…in terms of energy microwaves are much less energetic than infrared waves. Cooking by broiling is shooting infrared from the stove heating element to the skin of the food causing the skin to heat and cook the food. Thus if you should by your theory be more concerned with eating broiled food than microaved

    Ben wrote on February 22nd, 2010
  7. Also to add to the last comment.

    Fire is actually ionization of air. This air has very highly excited electrons. They fall back giving off infrared. This is why you see fire as red. When it is more energetic like on a bunsen burner, you get blue light. The blue light also means that there will be some ultraviolet, which is actually harmful to us. So when you are cooking over fire, you are using infrared, which is much more energetic than microwave.

    To repeat, the only problem with microwave ovens is the high power they provide. Microwave itself is not a problem.

    I hope to buy a microwave which actually changes the power intensity, instead of turning of the microwave lamp, when reducing power. Then I will be able to boil eggs in it. Currently the high intensity means that the food must be dipped in oil or water to actually cook it well. For heating it is fine.

    anand srivastava wrote on March 9th, 2010
  8. Just a few comments on an interesting discussion.

    First some geography. Strasbourg, the seat of the European Court of Human Rights (ECHR), is in FRANCE, not Austria. It is NOT a European Union court but a Council of Europe court and Switzerland is a member of the CoE (but not the EU).

    Second, Hertel’s paper was never published in a peer reviewed science journal. The Swiss found him liable for anti competitive actions by stating that people must not buy microwave ovens and throw away any they have, the article (in the Journal Franz Weber) showed a picture of Death pointing toward an oven. The ECHR did NOT find that Hertel was right, they did find that he had a right to publish his opinion and that the Swiss response was excessive (though this was a majority decision with dissenters being very vocal in their disagreement). The case is Hertel v. Switzerland, (59/1997/843/1049), Strasbourg, 25 August 1998. Google for a fuller, oficial report. BTW, Hertel’s article was in German, he studied just 8 people over 8 weeks and has refused to actually publish all the data from which he concluded. If you read his conclusions, they are actually full of “may” and “possible”.

    Norma Levitt was the lady who died after a transfusion of microwaved blood. The court case found that it was a blood clot, not the microwaving, that killed her. The point of microwaving is the speed, but the margin of error is much smaller. What probably happened is that the nurse microwaved the blood for too long (it needs only seconds) and literally cooked the blood. The result would be the same if you had put the blood in a saucepan on a stove. (Warner v. Hillcrest Medical Center 1995 OK CIV APP 123).

    Radiation seems to be a scary word, but is purely the emission of energy from a source. Sound is a form of radiation. Heat and light are forms of radiation even more energetic than microwaves. Many of you have radiation devices in your homes that are even called radiators. We are subject to light and heat in very beneficial ways. Your bog standard oven is also a radiation oven. Radiation is NOT a synonym for radio-active. Atomic bombs have little to do with microwaves, sorry Anon.

    There have indeed been many studies on microwaved food but nearly all come up with nothing significantly different from normal heating. This is very inconvenient for the anti microwave brigade but must not be ignored. Even the work done on milk and formula was more about the effects of cooking in localised hotspots, not microwaves themselves being dangerous. Further work on cooking brassicas (one study mainly on broccoli, another on other brassicas) showed nothing nasty either.

    Taste. Ah, microwaving heats to only 100C, locally higher, but generally doesn’t brown – which is part of the taste. Microwaved food therefore tastes, well, not happy. However boiled food tastes pretty awful too.

    Conclusion : there is very little real evidence that microwaving is bad. But it tastes bad.

    Comment 1 : please don’t be afraid of the word radiation. It is not the same as radio-active (which is just one of many forms of radiation).

    Comment 2 : please do the research, but complete it. If someone quotes a case where a woman died after being given microwaved blood, try to actually look at the case. So many sites misdirect their readers. Hertel’s court case is available on the net, it makes interesting reading and there are things that have never been published in there. Due to a lack of references to original documentation in most of the anti microwave sites, debunking sites are ironically the best sources.

    Kiwi-Ian wrote on April 26th, 2010
    • Great post! Some people seem to treat topics of interest like a religion (sorry if it offends), they will believe anything that is said as long as it’s what they want to hear. They will avoid science and ignore the facts if it means they have to drop their belief. (note: this last statement is not about religion, just pseudo science!).

      I am always very careful when I read sites about nutrition to make sure it’s someone who can back up what they say by good science or facts not just what sounds nice.

      Desdemona wrote on September 1st, 2010
    • Thank you for bringing some sanity to this discussion.

      Jake wrote on January 30th, 2011
    • Kiwi-lan, it’s nice to see someone actually paid attention in science class. Even though the idea that microwaving food is bad for you is not supported by facts, it still can taste bad.

      I am in complete agreement with you.

      Anonymous wrote on April 3rd, 2011
  9. This was a fascinating discussion… I have been thinking about the safety of the MW recently and I now am considering cutting back on my use of this oven device. However, a bigger concern should be our use of the CELL PHONES AND COMPUTERS and so on … there are so many things in our environment that are harmful to us – even the tanning beds that so many girls/women like to use – these cause cancer also … anyway thanks for sharing …

    Louise wrote on May 11th, 2010
  10. I work with radiation, you guys need to do more research on radiation. Did you know…..
    you get 1700mr of radiation just being alive from the sun(lovely grok sun)
    you get 1mr of radiation from a banana, when you eat it(poor monkeys)
    so from the microwave/cellphone/computer, you will not get even 1mr if you we sitting on using and looking at all three for the day, radiation is a natural part of this thing we call life and we would not survive without it, hope this shines some light on this so called dark subject.
    GROK on

    NUKER wrote on May 11th, 2010
  11. Hey NUKER I really hope we don’t work for the same company because your Nuclear knowledge isn’t very accurate. According to the Department of Energy, the average American receives about 360mr per year. The 1700mr you were talking about is mentioned by the same DOE report but is specific to a group of people living in the Northeast region of Washington State, and it’s mostly from Radon in the rocks and soil. As an actual Nuclear worker, the government allows me to absorb up to 5000mr per year of just ‘work related’ radiation and still not come remotely close to experiencing any health defect.

    Actual Nuke Worker wrote on May 11th, 2010
  12. So Actual Nuker Worker,

    I am a actual nuclear worker, but in Canada, where we have more stringent rules and regulations and the number one nuclear reactor in the world (candu reactor)and the place that makes all you radioactive isotopes for medical treatment. As per our CNSC(Canadian nuclear safety commission) we are allowed 2500mr a year, but only 10000mr over 5 years. And as per the Canadian nuclear research, which not to moch the American. As per them an average person that works outside, flys at least once per year and lives at an average altitude of 2500 ASL will receive approx 1700 mr/year, others who live at higher altitudes and fly many times a year can receive as much as 3500mr. I’m not saying that your information is wrong but there as always are different variable that affect the numbers. the point i was trying to get across was that the amount of radiation that gets emitted from today’s electronics like cell phones and LCD monitors is so minute that you could talk on the phone and watch T.V. all you life 24/7 and receive no adverse health affects. except in the case of unhealthy behavior of not eating a primal diet or any primal exercises.
    Grok On!

    Nuker wrote on June 25th, 2010
  13. I have always thought that Microwave ovens aren’t good for you but not because of absorbing radiation from it. (Just stand back from the door and microwave leakage testers are cheap) My concern is the free radicals microwaving creates.

    My Microwave does convection also so I use that as much as I can.

    David wrote on August 18th, 2010
  14. There are 826,000 entries dealing with the question of “Are microwaves safe or not?” Check them out for yourself and draw a conclusion. Good luck.
    74-year old.

    Arthur C. Jones wrote on November 25th, 2010
  15. Just found an interesting article in, written by Mark Session (?). Check it out.
    74-year old.

    Arthur C. Jones wrote on November 25th, 2010
  16. Microwaves kill. Run for your life

    flintstone wrote on December 30th, 2010
  17. To the people pointing to the patient who died from anaphylaxis after receiving a blood transfusion where the blood was heated in the microwave – I do not know if there even is such a case, however, I do know that there were reports of fatal anaphylaxis reactions to blood transfusions back in 1923, more than 20 years before the accidental discovery/invention of the microwave oven.

    Amanda wrote on January 14th, 2011
  18. I don’t use the microwave for much, aside from heating leftovers and the occasional popcorn. I have heard it’s really bad to use plastic in the microwave. But I honestly think you’re exposed to more dangerous things just walking outside breathing air. 😉 We can’t be afraid of everything, ya know?

    Denise wrote on January 19th, 2011
  19. lived without one for several years. couldn’t afford one in college, but later I did have a roommate for three years who had one – it was convenient but not something I need to live. I haven’t had one now for three years, and find heating things up in a covered cast iron skillet over low works great, doesn’t take too long either. I think a convection oven or toaster oven is a great investment, but wish they didn’t burn up every few years!

    bix wrote on January 19th, 2011
  20. Why microwave when you can just sautee leftovers in butter?

    SlimIcy wrote on January 19th, 2011
  21. I do not cook food with a microwave. The microwave, if I recall correctly, cooks by causing the individual molecules to vibrate rapidly, the heat being generated by friction between the molecules.

    Atoms and molecules vibrate — oscillate — more rapidly as more heat is applied. This leads me to think the reason a microwave cooks a food so quickly is molecular oscillation far beyond what a simple direct-heat source will attain. If so, a protein molecule, and all other nutritional molecules, will possibly be changed, or damaged, in some way not associated with the usual application of thermal energy to a food. Heat causes proteins to get bent out of shape, as it were, but we have evolved to use the proteins deformed by “normal” heat. I’ve always had a problem with my perception of the abnormal damage caused by a microwave oven and the problems that may be created within the body.

    Apropos to my argument is food irradiation: What kind of damage is being done to food molecules and how does the body react to them?

    Milk: not only does pasteurization destroy beneficial enzymes, the heat also kinks the proteins. Could this be another reason grocery store milk is far less nutrutional than raw milk? It could be some of the kinked protein molecules are damaged beyond the point of usefulness.

    Phocion Timon wrote on January 20th, 2011
    • Microwaves pretty much only act on water molecules. In addition, you defeated your own argument, assuming that microwaves act on molecules(as you said) the covalent bonds between the atoms remain stable unless the actual atom begins to oscillate. PLEASE think(or at least research) before you post.

      Anonymous wrote on April 3rd, 2011
  22. To Phocion Timon – I’m afraid that your explanation about the damage microwaves cause to molecules has a huge problem. Yes, heat causes atoms to oscillate (and vice versa), but as microwave ovens work mainly on the water content of food, they rarely heat to beyond 100°C (except local hotspots). Roasting and baking often heat to 180°C or more, frying heats to 200°C, the oscillation of atoms would therefore be even greater and MORE destructive for “traditional” cooking. Further, food browning (roasting, baking, frying) and charring (grilling, BarBQs)create pyrocompounds which are the most carcinogenic cooking compounds of all (and absent from microwaved food).

    Regarding food irradiation, there is practically no residual radiation (usually none at all), the main danger being that food looks good but there is no way of knowing what the level of natural contamination was before the irradiation – and many natural toxins are unaffected (e.g. listeria). Again, we have this fear of radio-activity over-riding actual reality.

    Re milk, I do not know if pasteurised milk is more or less nutritional than raw milk. Certainly homogenised (not the same thing) milk has a bad taste. However pasteurisation does kill a lot of nasty germs that would be more detrimental (e.g. fatal) than other effects of pateurisation. On balance, the benefits are in the pasteurisation camp.

    Kiwi-Ian wrote on January 31st, 2011
  23. Ok to the person/people comparing the microwave and cell phone to an atom bomb, you are blowing it completely our of purportion. Yes, on a nuclear level they are both using movement of cells to create heat, but the comparison ends there. While the microwave is using low energy magnetic radioactic microwaves (micro means small in latin) that create a small amount of movement in the surface it impacts on, the atom bomb is using nuclear fission, which as we know, is high-energy, large-wave emissions with a exponentionally higher amount of radiation and causes exponentially higher movement in the surface(s) that it impacts.

    If that was TL:DR here is the short version:

    Candle = Microwave
    Sun = Atom Bomb

    enough said.

    Trent Nye wrote on June 9th, 2011
  24. The dr.whathimakalit is stupid only one person researced

    Ot wrote on November 22nd, 2011
  25. Take a look at the next microwave you see, and notice how it has what looks like a mesh in front of the door? Ever wonder what that is for? It’s actually a whole bunch of quarter wave transformers. Those tiny little holes are actually designed to completely reflect the energy of the microwaves back into the body of the oven.

    I’m a little rusty on my microwave engineering courses, having not used the theory in about 8 years, but I do remember my professor giving us a lesson on how microwaves are indeed safe to use.

    Daniel wrote on February 8th, 2012
  26. Great Posts on this.
    Okay I’ll say it: I love my combi-microwave/convection oven! But I’m not sure if it loves me!
    As I move towards more raw food eating, there are many devices in the kitchen that don’t get used as much as in the past and the microwave is one of them…but when a last minute situation happens where two more steaks are needed then that little microwave with its modern defrosting system produces them without cooking the very quickly they can be brought to the bar-b-que or the stovetop. It’s a trade-off I’m willing to make as I freshly squeeze the orange juice.

    William Perrigo wrote on March 7th, 2012
  27. I never use a microwave, they just don’t sit right with me. I believe we don’t know enough about their effects and workings to be using them, and even if a study proved them to be dangerous (which as far as I’m concerned they are) it wouldn’t be published because they’re such a massive money maker. I think at the very least people should be required to pass a basic test before being allowed to purchase one – I heard on the radio that a man had to be rescued from his flat after he set it on fire whilst trying to microwave his pants dry :/ At the end of the day, if I dont need a microwave, why should anyone else?

    Mana wrote on September 17th, 2012
    • Because we’re not you. By that logic, since I don’t drink coffee neither should you or anyone else. Since I don’t consume alcohol neither should you or anyone else. Both are shown to have deleterious effects over time, yet people still consume them.

      Don’t assume that everyone’s time or lifestyle constraints are the same as yours – they’re not.

      I don’t actually cook meals in my microwave, but I do use it to reheat leftovers (they taste just fine and pretty much the same as fresh from the oven) and to melt things that need melting for recipes.

      That’s great if you’ve got the extra time to forgo using a microwave. I do not. I’m a full-time (12+ hours/day) working single mom of two young children. On my days off, Tuesday, Wednesday, and Thursday, most of my time is spent cooking enough food – primal of course – so that my kids and I have enough to eat over the weekend as I am not home for any meals. The rest of my time is getting them ready for kidergarten and preschool and doing laundry and cleaning…you get the picture.

      I leave for work at 4:30am and usually don’t get home until 5 or 6. It’s simple economics, really. I don’t have the time to do it all, so I pick my battles, so to speak. If I need to use a microwave to reheat, so be it.

      To be perfectly honest, I haven’t yet read any compelling research that has caused me to alter my opinion that microwave ovens are dangerous. If and when I do, then I’ll figure something else out. Until then I’ll be satisfied that my kids aren’t eating grains, legumes, or processed crap. That will have to suffice for now!

      Egglet wrote on November 29th, 2012
  28. You know, its all well and good to proclaim the benefits of stove-top heating and all, but for some people, its less a matter of choices. I work 8-12 hours a day in a small shop where we are unallowed to have a full stove and barely have room for a microwave, toaster, and small fridge. As long as there is no scientific evidence of life-altering/life-threatening consequences found to microwave use, I have to stick by what I have in order to eat at a reasonable budget

    Frizzy wrote on March 26th, 2013

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