As a fitness professional, I often get asked about Microwave Dangers. Questions like, “Is using the microwave oven bad for my health?” “I’ve heard microwaving changes the molecular structure or water/ food making it less nutritious or unhealthy. Is that true?” “Does the microwave cause cancer?”
My reply to any and all questions like this is always… “It’s NOT what myself or anyone else BELIEVES, it’s what the scientific EVIDENCE says.”
In this post I’m going look at the Top 5 most common claims about Microwaves dangers and show you how the current body of scientific evidence does not support these claims and proves them to be erroneous.
Put simply, what you’ll find when you go to the sources making these claims about microwave oven dangers is that they provide NOT a single credible source in a peer-reviewed journal to justify their claims. However, THIS post gives you the mother load of peer-reviewed journal citations and credible sources.
Now, lets get things going by first (briefly) exploring how a microwave over works in order to help you better understand the claims (vs. the actual evidence) about microwave dangers.
How Does a Microwave Oven Work?
The typical domestic Microwave oven has a power rating between 600 and 1,500 watts. More watts means more heat, while lower power means longer cooking time. Typical domestic microwave ovens operate at a frequency of 2.45 GHz with an output power of 500W. (7)
A microwave oven uses “dielectric heating” to cook food. (1) This is accomplished by using microwave radiation to heat polarized molecules within the food. This excitation is fairly uniform, leading to food being more evenly heated throughout (except in dense objects) than generally occurs in other cooking techniques. (2).
In other words, molecules that are electric dipoles, of which water is the most efficient, rotate back and forth; the friction between them creates heat. This process is “dielectric heating.”
The literature reveals that microwave heating occurs by two mechanisms, which are dipolar polarization, and ionic conduction (Kingston and Jassie, 1998, Mingos and Baghurst, 1991 and Taylor et al., 2005). Dipolar polarization is by which heat is produced in polar molecules like water. Dipoles align themselves by rotating with the electric field associated with waves… In conduction, dissolved charged particles (ions) in a sample oscillate back and forth under the influencing electric force of microwaves creating an electric current. This current faces internal resistance because of collisions of charged species with neighboring molecules or atoms, which cause materials to heat up (Metaxas, 1996 and Ponne, 1996). The conduction principal has much stronger effect in comparison to dipolar polarization for heat producing capacity (Keiko, 2003).(8)
1. “Microwaves Leak Dangerous Levels of Radiation”
What The Evidence Says:
– Domestic microwaves do leak some radiation, which the US Food and Drug Administration (USFDA) allows for because they are far below the level known to harm people. Microwave energy also decreases dramatically as you move away from the source of radiation. A measurement made 20 inches from an oven would be approximately one one-hundredth of the value measured at 2 inches.(6)
– “Based on the survey results, several studies and the fast decay of radiated power density with distance from the oven, the conclusion was that user exposure to RF radiation from microwave ovens is much less than the general public exposure limit set by most international standards… and that a detrimental effect on health is an unlikely result of exposure to radiation from microwave ovens.” (3)
– The design of modern microwave ovens is such that the microwaves should be contained within the oven, but it is still possible for some leakage to occur around the doors of certain microwave ovens. Generally, the required design of oven doors should restrict this leakage to a level well below that recommended by the Australian/New Zealand Standard… The recommended limit is conservative and includes significant safety factors, so that even leakage levels appreciably above the limit will have no known effect on human health.(4)
– All new microwave ovens produced for sale in the United States must meet the Food and Drug Administration/Center for Devices and Radiological Health (FDA/CDRH) performance requirements in Title 21, CFR, Part 1030.10.(26)
The USFDA requires all microwave ovens to have two independent interlock systems that stop the production of microwaves the moment the latch is released or the door opened. In addition, a monitoring system stops microwave oven operation in case one or both of the interlock systems fail. (6)
– There is no residual radiation remaining after microwave production has stopped. In this regard a microwave oven is much like an electric light that stops glowing when it is turned off. (6)
– Surveys by organisations providing testing services have shown that microwave oven leakage levels in excess of the recommended limits are rare and an oven in good condition and used correctly is safe.(5)
BOTTOM LINE: Properly working domestic microwave ovens do NOT leach harmful levels of radiation. Organizations such as the USFDA and the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) have strict standards, and regular testing procedures in place to ensure their safety standards are upheld.
“Absolutely no negative health effects of microwave heating have been shown conclusively in all these years since microwave heating was started in the 50s.” Ashim Datta, a professor of biological and environmental engineering at Cornell University and the author of The Handbook of Microwave Technology for Food Applications.
2. “Microwave Radiation Can Cause Cancer; Damage Human Reproductive System, Immune System and Central Nervous System”
What The Evidence Says:
– Accidental exposure to high levels of microwave energy can alter or kill sperm, producing temporary sterility. But these types of injuries – burns, cataracts, temporary sterility – can only be caused by exposure to large amounts of microwave radiation, much more than the 5mW limit for microwave oven leakage. (6)
– A 2003 literature review published in the Journal of Microwave Power and Electromagnetic Energy looked at the recent medical and scientific literature (from mid-1998 through 2002) dealing with possible effects of low-level radio-frequency (RFE) on brain tumors and malignancies, leukemia, other cancers, and the central nervous system concluded that “the evidence for any proven health effects (related to the topics above) of low-level RFE exposure is minimal.” (9)
– A 2008 literature review published in the Journal of Hygiene and Environmental Health reviewed the recent medical and scientific literature (from mid-1998 through early 2006) dealing with possible effects of low-level radio-frequency (RFE) (3 kHz to 300 GHz) on cardiovascular, reproductive, and immune systems concluded that “there is only weak evidence for a relationship between RFE and any endpoint studied (related to the topics above), thus providing at present no sufficient foundation for establishing RFE as a health hazard.” (10)
– A 2005 study published in the American Journal of Epidemiology concluded that “extremely low frequency electromagnetic fields from commonly used household appliances are unlikely to increase the risk of brain tumors.” (19)
– According to the USFDA, “Less is known about what happens to people exposed to low levels of microwaves. Controlled, long-term studies involving large numbers of people have not been conducted to assess the impact of low level microwave energy on humans. The fact that many scientific questions about exposure to low-levels of microwaves are not yet answered require FDA to continue to enforcement of radiation protection requirements.” They go on to recommend “Consumers should take certain common sense precautions.” (6)
BOTTOM LINE: Absolute claims about household microwaves causing cancer, or damaging human reproductive, nervous or immune system are at this point completely unsubstantiated, as the current evidence for cause and effect in the area is virtually non-existent. That said, one would do best to follow the USFDA’s recommendation of taking “common sense precautions” like not standing directly next to the microwave while it’s on, since, as stated above, it’s been shown that standing just 20 inches away – that’s less than the average adults arm length – from a microwave oven would be approximately one one-hundredth of the RF radiation value measured at 2 inches.
“This type of radiation is non-ionizing, which means that it isn’t the type of “radiation” you’d associate with Homer Simpson and Chernobyl — it’s in the form of waves.” Ryan Andrews, the Director of Education at Precision Nutrition
3. “The Microwave Alters/ Reduces/ Kills Nutrients in Food”
This type of claim likely stems from a 1975 study published Journal of Food Science, which stated that the shape and texture of both carrot and broccoli halves appeared to change while those cooked conventionally more nearly resembled the shape of the stalk or root. (28)
It’s also likely this type of claim comes from the large number of studies – several are described below – which find changes to the nutritional content of food that has been microwaved. However, as you’ll see when we actually look at the evidence, changes to the nutritional content of food happen whenever any food is cooked by any method. So this reality has more to do with the act of cooking food than with the specific cooking method.
(First) What the Evidence says about Cooking Food (vs. Raw):
– A January 2008 report in the Journal of Agriculture and Food Chemistry said that boiling and steaming better preserves antioxidants, particularly carotenoid, in carrots, zucchini and broccoli, than frying. (12)
– Another 2002 study published in the Journal of Agricultural and Food Chemistry showed that cooking carrots increases their level of beta-carotene. (13)
– A 2002 study published in the Journal of Agriculture and Food Chemistry found that cooking boosts the amount of lycopene in tomatoes. (14) Additionally, Rui Hai Liu, an associate professor of food science at Cornell University who did the study stated in this article, “Cooked carrots, spinach, mushrooms, asparagus, cabbage, peppers and many other vegetables also supply more antioxidants, such as carotenoids and ferulic acid, to the body than they do when raw.” The reason, he says: “the heat breaks down the plants’ thick cell walls and aids the body’s uptake of some nutrients that are bound to those cell walls.”
What the Evidence Says about Microwave Cooking:
– A 2003 study published in The Journal of the Science of Food and Agriculture found that broccoli cooked by microwave — and immersed in water — loses about 74 percent to 97 percent of its antioxidants. However, when steamed or cooked without water, the broccoli retained most of its nutrients.(11)
– A 2004 study published in the International Journal of Food Properties said there was no difference in iron, phosphorus or calcium content of spinach in the three different preparation methods: conventional boiling, pressure cooking and microwaving. (15)
– A 1982 study in Critical Reviews in Food Science and Nutrition looked at the effect of microwaves on nutrient value of foods and stated, “Overall, the nutritional effects of microwaves on protein, lipid, and minerals appear minimal. A large amount of data is available on the effects of microwaves on vitamins. It is concluded that there are only slight differences between microwave and conventional cooking on vitamin retention in foods. In conclusion, no significant nutritional differences exist between foods prepared by conventional and microwave methods. Any differences reported in the literature are minimal.” (21)
– A 2010 study published in the Journal of Food Biochemistry looked at the effect of microwave, boiling and pressure cooking on total antioxidant capacity and total phenolics content of seven vegetables: carrot, cauliﬂower, pea, potato, spinach, Swiss chard and tomato. The researchers observed that all three cooking methods cause some loss to phenolic compounds, however, microwaving and pressure cooking is less detrimental to nutrients than boiling. (16)
– A 2005 study published in Food Chemistry showed that boiling, steaming and microwaving had no difference on the content of phenolics and antioxidants in pepper, squash, green beans, peas, leek, broccoli and spinach.(17)
BOTTOM LINE: Based on the evidence, 1) Cooking in water seems to be more of a negative than cooking in a microwave, at least as far as preserving nutrients in vegetables is concerned. 2) Microwave cooked food may retain vitamins and minerals better than stove-top-cooked food because the microwave zaps food quickly and without much water. Plus, if time is a factor, microwaving is much quicker too!
“Some nutrients do break down when they’re exposed to heat, whether it is from a microwave or a regular oven. Vitamin C is perhaps the clearest example. So, as a general proposition, cooking with a microwave probably does a better job of preserving the nutrient content of foods because the cooking times are shorter.” The University of Harvard Medical School (18)
4. “Microwaving in plastic is Dangerous because it can cause toxic chemicals (like phthalates and dioxins) to leak into your food”
What the Evidence Says:
– The FDA, recognizing the potential for small amounts of plasticizers to migrate, closely regulates plastic containers and materials that come into contact with food. Before approving a container, the FDA conducts tests to make sure that it doesn’t leak unsafe amounts of any substance into food. (18)
– According to the American Chemistry Council, “All plastics intended for food use — whether designed for microwaving or not — must meet stringent U.S. Food and Drug Administration (FDA) safety standards before they are allowed on the market. When manufacturers develop individual plastic packaging products, they often conduct additional testing based on a product’s intended use. Choosing to microwave with a plastic item not labeled for microwave suitability isn’t necessarily “unsafe,” but you won’t have the assurance of knowing the item was tested and evaluated for this purpose.” (20)
BOTTOM LINE: If a plastic container is marked “microwave-safe” or carries a microwave icon on it, it’s been specially designed and tested to NOT toxins into your food and withstand microwave heat without melting or warping.
Additionally, The Harvard Medical School Recommends some things to keep in mind when using the microwave:
- Most takeout containers, water bottles, and plastic tubs or jars made to hold margarine, yogurt, whipped topping, and foods such as cream cheese, mayonnaise, and mustard are not microwave-safe (and could potentially leak chemicals into your food).
- Microwavable takeout dinner trays are formulated for one-time use only and will say so on the package.
- Don’t microwave plastic storage bags or plastic bags from the grocery store.
- A recycle symbol does not mean a container is safe to use or reuse in the microwave oven. Only a microwave-safe icon or wording to that effect does.
5. “Microwave Ovens alter the molecular structure of food and Water in harmful ways”
What the Evidence Says:
– There is ZERO evidence to support either claim that microwave cooking changes the structure of food or water. And, the burden of proof is ALWAYS on the one(s) making the claim – It is they (the claimer) who must reject the null hypothesis.
– Concerning the effects of Microwaves on Food: The researchers in a 1995 study published in the Journal Food Chemistry did a toxicity experiment on rats using human food. In this study, the researchers intentionally subjected the food to misuse treatment by reheating in a microwave repeatedly to make sure to concentrate any potentially harmful substances. Their criteria to assess toxicity included clinical observations, ophthalmoscopy, growth, food and water intake, haematology, clinical chemistry, urinalysis, organ weights, micronucleated erythrocytes in bone marrow, gross examination at autopsy and microscopic examination of a wide range of organs. Their results indicated “No adverse effects of the diets cooked by microwave compared with those cooked conventionally.” (22)
– Concerning the effects of Microwaves on Water: According to Louis A. Bloomfield Ph.D., a Professor of Physics at the University of Virginia and the author of the book How Everything Works: Making Physics Out of the Ordinary, “Microwaves don’t affect the molecular structure of the food, except through the thermal effects we associate with normal cooking (e.g., denaturing of proteins with heat and caramelizing of sugars). That’s because, like all electromagnetic waves, microwaves are emitted and absorbed as particles called “photons.” The energy in a microwave photon is so tiny that it can’t cause any chemical rearrangement in a molecule. Instead, it can only add a tiny amount of heat to a water molecule.” (23)
In other words, stating that microwaving would cause the structure of the water molecules to tear apart and cause the water to essentially decompose into its component hydrogen and oxygen, as occurs in electrolysis, is an incredible claim that’s also incredibly unsubstantiated, much less to go farther and make definitive claims as to what what the dangers would be even if it did.
Plus, not only is this claim completely unsubstantiated, it’s just plan WRONG because a microwave oven passes “Non-Ionizing” microwave radiation (27) through food. Brian Dunning, in his “Are Microwave Ovens Safe?” episode of Skeptiod, does a great job of explaining this reality in order to highlight how demonstrably wrong this type of claim is:
“Probably the most flagrant error that the Microwave Militia propagates is that microwaved food or water contains what they call “radiolytic compounds” — new chemicals created by the tearing apart of molecules in a microwave. These new chemicals are said to be dangerous, cancerous, radioactive, unnatural, or otherwise harmful. This is a demonstrably false claim. Radiolysis, which is a real process and which the Militia believes creates these radiolytic compounds, is the process by which molecules are dissociated under ionizing radiation. Water can be dissociated under ionizing alpha particle bombardment, which is a natural process. Microwave radiation, as mentioned earlier, is not ionizing radiation. It is thus scientifically incapable of causing radiolysis. The differences between microwave radiation and alpha radiation are huge. With the claim that microwaves cause dissociation of water molecules, the Microwave Militia is either deliberately lying, or they are grossly ignorant of the very subject on which they claim superior expertise.”
– The fact-checking website Snopes debunked the claims regarding the two pictured plants (below) that many of the Microwave Dangers websites love to talk about: one that was given microwaved water and a second plant that received purified water.
As the internet story goes, the pictures are from a science fair project (done in 2006) done by the granddaughter of an unknown man who wrote the letter sharing this story with the world. Supposedly she (the granddaughter) thought that the structure or energy of water may be compromised by the microwave. And, over the course of 9 days, as you can see by the photos, the plant given microwaved-water shriveled and died, supposedly due to the adverse effects of “microwaved water.”
Now, not only is this whole story pure internet rumor, the testing methodology used doesn’t nearly represent “good science,” therefore, making any conclusions drawn from it erroneous.
Moreover, the folks at Snopes claim to have replicated this experiment in a much better and more controlled manner.
According to their website, they took nine healthy plants, three each of three different plant varieties — with one member of each set recieving a differnet water treatment all from the same water source and temperature.
3 plants (one from each set) were given unboiled room-temperature water
3 plants (one from each set) were given microwave-boiled water, cooled to room temperature
3 plants (one from each set) were given stove-top boiled water, cooled to room temperature
In their experiment, the person watering the plants didn’t know which water was which in order to “blind” them, which eliminates any possible influence from the waterer.
At the conclusion of their experiment, the “waterer” (who was blind to knowing which water was which) was asked to pick out the plants that faired best within each of three watering groups, 2 out of 3 plants chosen to appear most healthy, were plants that received microwave-boiled water. Go here to read more about the Snopes “plant watering” experiment and findings, and see the photos of the plants.
Note: I’ve provided an overview of the Snopes experiment, not to claim it a somehow “valid evidence” – It’s certainly not, as it’s not published in any peer-reviewed journal – but to display what a reliable study looking at the subject matter in question would have to look like in order for anyone to be able to draw any reliable conclusions from.
BOTTOM LINE: In regards to food, there is no evidence to support that microwave cooking changes the structure of food, much less in an unhealthy manner. And, the evidence we do have shows exactly the opposite!
In regards to water, as Snopes put it, “Water heated in a microwave oven is no different in ‘structure or energy’ than water heated with a gas flame, on an electric stove, or over a wood fire: it’s just water, plain and simple.”
Additionally, Brian Dunning, the host of the Skeptiod, which won the 2012 Best Science Podcast in the first annual Stitcher podcast awards, puts this ridiculous myth to bed by issuing a very legitimate challenge:
“This whole paranoid suggestion is based on the presumption that a microwave oven somehow changes or poisons water. If true, wouldn’t you be able to perform some kind of a test on water, and see if it has ever been microwaved? Water is H2O, whether it’s ever been microwaved or not. But here’s an even deal for you. If you truly believe that H2O carries some permanent damage as a result of being microwaved, and that it’s possible to detect this damage through any means you choose, there’s a million dollars in it for you. As you may know, the Skeptoid podcast is a qualifying media outlet for the James Randi Educational Foundation’s Million Dollar Paranormal Challenge. I’ll walk it through for you and I’ll become your biggest cheerleader. Are microwaves really a danger to humanity? If so, it would be immoral for you to do anything else but take that million dollars and use it to educate and save the world.” (25)
As you’ve seen, all 5 of these much too common “big” claims about microwave dangers, which I addressed above, certainly don’t have “big” evidence to support them. When these claims are made, you’ll clearly see that there is either zero evidence provided to support them, or very poor evidence (like non-published or non-peer-reviewed “studies”) is cited as if it is somehow “legitimate” “irrefutable” evidence. It is for this reality that we don’t put any weight behind these claims, and remain very skeptical of anyone who repeats these claims.
Put simply, we don’t care about what so and so says, we’re concerned about the VALIDITY of what so and so says. That’s exactly why, in this post, you were provided with plenty of very legitimate and reliable evidence to validate the statements given in the “Bottom Line” sections.
Finally, to take us home, here’s one last piece (of wise words) addressing the claims of “Microwave dangers” from Brian Dunning
“One clue that might encourage you to regard these claims with some skepticism is that fact that ever since microwave ovens came on the market in 1954, not one person has ever exhibited a single symptom of any illness resulting from having eaten microwaved food, or from having used water that had been microwaved. Burns are the exception, but burns are caused by heat from any source; that’s not unique to microwaves. But if you believe the claims by the anti-microwave fringe, whom I call the Microwave Militia, practically everyone on the planet should be gravely ill with cancer, radiation poisoning and malnutrition.”