Updated: Mar 3, 2019
It’s a controversial subject with many experts piping in about the hazards of the microwave oven, while others say they are safe. But the questions and concerns linger on your mind every time you turn one on. Are you hurting your health, or is this technology really safe? Let’s face it, microwaves are handy-dandy gadgets that heat your food quickly. The technology has been around since the 50’s, and the FDA began regulating them as they became commercialized in the early 70’s. Since that time they have been the source of much debate in the health community.
I guess the idea of “zapping,” “nuking,” or otherwise heating your food using microwave radiation can seem a little questionable to your health, right? Many think immediately about Three Mile Island in 1979, Chernobyl in 1986 or Fukushima in 2011. So, in this article, let’s take a look at the evidence behind some of the most common microwave concerns and discuss if we are mini-Chernobyl’s waiting to happen every time we heat lunch.
First, though, let’s start with the basics. How do microwaves work?
Microwave ovens use microwave radiation to heat food. Yep, sounds a bit scary huh? But it’s really not, you see electromagnetic or 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). They are not nuclear. On the EM spectrum, microwaves fall between radio and infrared waves (see here). That’s important to understand because it’s the wave length frequency that determines whether it’s healthy for you or not. Obviously the wave lengths (which are shorter) at the x-ray side are quite harmful when prolonged exposure is concerned. But at the longer wave length end, it’s a different story.
Just so that we understand, each level of radiation has a different effect on molecules in which they interact with, as well as a different ability to penetrate tissue or other materials. Microwaves from a microwave oven contain only enough energy to induce something known as molecular rotation or resonation. This is the lowest energy form of interaction. They don’t have enough energy to induce molecular vibrations, electron excitation, or ionization so technically they cannot cause cancer, but more on that later. Where microwaves have the greatest effect is on water molecules. Microwaves cause a rapid rotating water molecule which transfers energy into heat. Essentially by rapidly rotating water molecules you create heat which in turn heats your food.
As I have mentioned the one concern people have about microwave ovens is the simple fact that they emit microwaves. The concern is that any exposure to microwave radiation is linked to DNA damage, cancer and infertility. Well, the evidence is mixed; most published research concludes that low-level microwave exposure doesn’t really present a significant risk to human health. But as many experts point out, exposure to microwaves does in fact harm your cells and heat them up, destroying the DNA and who knows what else. And this is true. If you somehow crawled into a microwave and it was activated you would die. No question. Just the same as if you crawled into an oven cooking at 400 degrees. You would die. So the issue is not whether something INSIDE a microwave can kill you, the problem is whether anything on the outside will harm you. In other words, if the oven were to leak some microwaves, would that harm you?
Well, first of all, unlike an oven where you open the door to be met by a sudden gush of eye penetrating heat, when a door to a microwave is opened the microwaves are immediately terminated. So when you open the door, all the microwaves are gone. That leaves us with the closed and operating microwave right? So, the first question is do they leak. Obviously the microwave itself is designed to eliminate any leaking but that does not mean they do. Consequently, the FDA regulates the level of leaking so that they do not leak more than a very small amount.
The allowable leakage is 5 mW/cm2 (milliwatts per square centimeter) of radiation at a distance of 2 inches from the microwave. So yes if you pressed your face up against the microwave to watch the food heat up it would leak a little and yes you could get a little microwave. But we should put that into perspective. Your cell phone also uses radio waves, in the same approximate wave length. 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.
Ok, so a little math here. A μW/cm2 is considered a microwatt, while a milliwatts is mW/cm2. The difference is 3 decimals to the left or 1000. Therefore a 10.5 μW/cm2 is .0105 mW/cm2. Based on these numbers, having a cell phone in your pocket on silent mode exposes you to roughly the same level of microwave radiation (averaged at 5.425 μW/cm2) as standing 2 inches from an average microwave while it’s heating! However, while the microwave oven only cooks your food for a few minutes, you may be exposed to microwaves from your cell phone all day and sometimes all night long. Over years of doing this, we have indeed found some negative effects to cell phone use. Keep in mind that exposure to microwaves in cooking is limited to only the cooking time, while your phone is constant. Literally the difference is similar to passing your finger quickly through a candle flame or holding it in place for 15 seconds. One would harm you, the other would have no effect.
It’s also worth pointing out that as you move away from the source the microwaves rapidly dissipate. At 20 inches for instance you would receive about 1/100 of the measurement taken at 2 inches, so, to avoid microwave radiation don’t put your face on the microwave door while it is on, or the oven door for that matter. And while I’m at it, take the phone out of your pocket and put it at least 20 inches away from you during the day because that cell phone appears far more harmful than your microwave oven does.
Of course both sources are considered non-ionizing sources and so, unlike that TSA X-ray scanner that you walk through at the airport, the source of the microwaves are considered safe.
Now we understand this, it is also important to acknowledge that real microwave emissions seem to stay below the federally mandated maximum, so again, your cell phone is far more a threat to your health than your microwave. A study published in 2013 on microwaves for instance 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. A 2001 survey of microwaves 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.
So now we have determined that a normally performing microwave is safe, let’s talk about the effect of microwave heating on food because that’s where the pundits often go next. One claim is that microwaves can “denature” proteins, making them toxic to the human body. In some respects that is true. Any protein that is heated will denature. And yes, any food cooked in any device will destroy its vitamin content. But this is not unique to microwaved food, it is consistent with any food that is heated or cooked. Denaturing a protein does not necessarily make a food toxic by the way. The term denatured, in its simplest explanation, means that the protein or its building block the amino acid has lost its three-dimensional shape. The amino acids are still there, still bound together, but heating them up untangles their shape a little.
Other things that can denature proteins include changing the pH of the meat. You could argue that heating does that, but so does digestion! You see part of the digestive process is the denaturing of the proteins eaten so they can be digested. This process allows the digestive enzymes (produced by you) a fighting chance to breakdown the amino acid so it can be absorbed in the gut and then used to provide a nutritive benefit.
I think what people have in mind when they refer to “protein denaturation” is actually something called post translational amino acid isomerization. Yep a whopper of a term and a completely different process from denaturation. The process refers to changing a standard L-amino acid (left forming) into a D-amino acid (right forming). In the body we tend to use the L- form of amino acids mostly, 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. Some people suggest that this can be a cause of cancer.
There are studies which show that large amounts of isolated D- amino acids fed to rodents show harmful effects, but there again isomerization occurs in any food overheated and in any process, not just microwave cooking. In reality, it’s actually deep fried processed foods such as chips that are more likely to cause cancer than overheated meat. Additionally, many foods (such as raw dairy from ruminants and some fruits and vegetables) naturally contain low levels of D- amino acids and that is considered healthy.
Bottom line. 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. Additionally, the general consensus seems to be that if more D- amino acids are formed, it is due primarily to overheating which could happen on your grill, in your oven or over an open fire pit.
So, does a microwave kill the foods nutrition? Actually, because microwaving is quicker it’s likely that more nutrients are preserved versus longer cooking methods. As far as vitamins are concerned, their mortal enemy is heat. Minerals are generally unaffected by any cooking method and antioxidants, and plant phenols also breakdown when heated, no matter what method is used. Fact is heat destroys vitamins.
If we get right down to it, boiling is likely the least likely method to retain nutrients. This is especially true for the water soluble vitamins since they are um….water soluble. Most experts would agree that steaming is a better cooking method than boiling.
As a final interesting point, one study, published in 1995, used a rat model to look at the overall effects of a microwaved diet. 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. At the end of 13 weeks, they found no adverse effects of microwave cooking on the rats. Now that does not mean that heating up certain oils, especially vegetable oils, would not have long term health ramifications! But there again, it was never about the method of heating, but more the method of production.
Now what is most definitely dangerous is heating the plastic containers and wraps that many microwavable food is packaged in, and in which you are supposed to cook them in. Here we have a real issue because one of the worst contaminants is something called BPA, or bisphenol A. BPA is an estrogen-like compound used widely in most all hard plastic products, and certain phthalates (pronounced THAL-ates), which include a wide range of chemicals that, among their many uses, soften plastic. While a very real danger exists when using water bottles and other plastic containers, our highest exposure comes from our daily diet. The problem is that molecules of BPA can migrate from containers into food, especially when the containers are heated and the foods are acidic (like tomatoes) or fatty (like meat). So eliminate your plastic containers and use only glass ones, especially if heating food in a microwave or any oven for that matter.
So really, microwaves aren’t as dangerous as some people make them out to be. Yes, they’re another source of microwave radiation in your home along with your television, your cell phone, your wireless router and your radio, 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. If you feel that electromagnetic wavelengths affect you negatively I suggest wearing an EMF pendant, which can be very effective.
Bottom line, there’s no evidence that a normally functioning microwave adversely affect the nutrient profile of foods more than other cooking methods.
If you’re still skeptical of microwaves after reading this, by all means – use whatever cooking method makes you comfortable. But microwaves are used everywhere, from treating a sore muscle, to detection of a speeding vehicle, to televisions and radios and of course your cell phone. So if you are one of those people who tout the destructive elements of microwaves, but use a cell phone…well!
Overall, if you enjoy the convenience of a microwave, don’t be afraid to use it to reheat food or warm beverages.