If you’ve ever surfed the internet for information on health and nutrition, there’s little doubt you’ve come across scare stories about microwave ovens. Online natural health “experts” claim that microwaves will “zap” your food, deplete it of important nutrients and alter its molecular structure in dangerous ways. They also warn that microwave exposure and eating food cooked in microwave ovens will cause harm to your body and even cause cancer!
Is there any truth to any of these reports? Why are some people so paranoid about an appliance that has been used safely by millions of people for decades? Should you stop using a microwave oven for reheating leftovers, making frozen dinners or cooking your vegetables, and warming baby bottles among other things?
These are important questions because your health is of the up-most importance and the microwave oven, is unquestionably one of the greatest time savers and conveniences you can have in your kitchen.
We will look at each microwave myths one by one and support its safety with facts, science and evidence, not urban legends and fear mongering.
What Started all the Microwave Scare Stories?
Rumors are often started and circulated on the internet without anyone ever confirming the source. Did you ever get one of those random emails that said something like, “10 reasons to throw out your microwave” and then forward it right on to a friend, just assuming it was true?
A large part of all the microwave alarmism today can be traced back to a single story that was spread on the internet until it went viral and was eventually accepted as factual. It’s the story of the infamous “Swiss research” done by “food researcher” Hans Hertel, who allegedly performed his own private study to see how microwaved foods affected the results of blood tests. A typical iteration of the story goes like this:
“The use of microwave ovens in cooking can alter the structure of nutriments in foods, making it difficult for the organism to make use of them. Hertel discovered that food cooked or thawed in a microwave oven could cause changes in the blood, indicating that a process of illness is developing. Similar changes are also found in cases of cancer.”
“The best studies about the use of microwaves to heat food were purposely kept from consumers. Hertel was efficiently “gagged” by Swiss microwave oven producers. For over 10 years, Hertel has fought for the right to tell the world what he’d discovered.”
The best studies are not kept from consumers, they are peer reviewed, replicated and published in scientific journals where we can actually look them up. Alas, we cannot access Hertel’s “research” to judge its validity because it was never published.
In fact, by Hertel and his follower’s own accounts, this “study” was just himself, Bernard Blanc (who later recanted) and six of their buddies who locked themselves in a hotel room and conducted a personal and arguably non-scientific and non-controlled experiment. This is not real research; it was never verified or replicated by other researchers. Yet you see Hertel quoted in almost every “microwaves equal death” article on the Internet, a good tipoff that everything else in the article is suspect as well. So with that said, let's begin with myth numero uno.
Myth 1: Microwaving Foods Make Them Carcinogenic (Cause Cancer)
Microwave radiation is production of thermal energy, (heat). A lot of people confuse radiation and radioactive, and they are not the same thing. Celeste Robb-Nicholson, M.D. from the Harvard Health Review explains:
“Microwaves do not cause cancer. They’re a form of non-ionizing radiation and thus cannot ionize tissue. Microwave ovens use low-frequency waves of electrical and magnetic energy to produce heat to cook food. They don’t make food radioactive, nor do they trigger cancer-causing genetic mutations.”
A search of the medical literature brings up absolutely nothing linking microwave cooking to cancer.
The research says that concern over cancer causing compounds such as heterocyclic amines (HCAs), and polycyclic aromatic hydrocarbons), would be better directed toward educating consumers on the charring and blackening that occurs when grilling or barbecuing muscle meats, rather than cooking the meat in microwave ovens.
In fact, cooking in a microwave can actually reduce the formation of HCAs. This quote comes from the National Cancer Institute (www.cancer.gov):
“Studies have shown that microwaving meat prior to cooking helps to decrease mutagens by removing the precursors. Meats that were microwaved for 2 minutes prior to cooking had a 90-percent decrease in HCA content.”
Myth 2: Microwaves Leak Radiation
Although microwaves are a form of non-ionizing radiation, you wouldn’t want prolonged exposure to them at high power any more than you’d want to stick your head in the conventional oven on high and leave it there. You also wouldn’t turn the temperature up in your house to 325 degrees to roast a turkey – the idea is to cook the bird, not you. So if the microwaves get of the oven, could they hurt you then?
In the early days of the microwave oven, leaks were more of a concern due to imperfect oven designs. Due to federal standards and improved engineering today, experts agree that this is now a non-issue. According to the FDA, there is little cause for concern about microwaves leaking from the oven unless the door hinges, latch or seals are damaged. (you can always buy a leak detector if you’re paranoid).
If you’re still worried, simply back away from the microwave while it’s running. Microwave energy rapidly dissipates as you move away from the source. Also, the way microwaves are manufactured, the second the door is open the device shuts down and no radiation leaks out after you’ve opened the door.
Myth 3: Microwave Alter the Molecular Structure of Food
The molecular changes caused by cooking a food in a microwave are no different and no more harmful than the heating of a food any other way.
A Dutch study in 1995 that was published in the journal Food Chemistry conducted a toxicity experiment on rats using human food that found the opposite. The researchers intentionally subjected the food to misuse treatment by reheating in a microwave repeatedly to make sure to concentrate any potentially harmful substances. The tests were exhaustive and no harmful effects were found:
“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. The results indicate no adverse effects of the diets cooked by microwave compared with those cooked conventionally.”
Myth 4: Microwaves Remove Nutrients out of Food
All forms of cooking can destroy nutrients, but contrary to what most people know, microwave cooking can actually preserve nutrients better than some other cooking methods like boiling. Minerals hold up particularly very well.
At least two studies did raise concern over major flavonoid losses in broccoli and one over vitamin C. One of the studies showed a 97% loss of flavonoids in the broccoli, which has been the basis of the “microwaves zap nutrients” myth ever since. The major nutrient losses were created by cooking the veggies in a lot of water.
Nutrient losses while microwaving depend mostly on cooking power, cooking duration and volume of cooking water. The studies did not conclude that you shouldn’t cook in a microwave oven, they concluded that steaming is the preferred method for retaining the most nutrients in vegetables and that if you cook broccoli or other veggies in a microwave, don’t overcook them and don’t cook them in water.
Vitamin losses from cooking meat in the microwave have also been studied. A 1998 study from Japan showed a 30% loss of vitamin B-12 from cooking meats in a microwave. However, it’s not a massive nutrient loss compared to boiled vegetables and since B-12 is heat sensitive, similar losses occur from conventional cooking as well, so once again it’s not a microwave-exclusive problem.
Many people don’t care for microwaved meat anyway (texture is rubbery), but all things considered, studies say that microwaving your veggies is not a bad way to cook them. In fact, some research says microwaving retains more nutrients due to the fast cooking times. A 1982 study by Cross and Fung published in Critical Reviews in Food Science and Nutrition concluded:
“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.”
Myth 5: Microwaves Denatures Protein
Here’s an issue that concerns some of us bodybuilders and fitness minded folks: Does microwave cooking damage or denature protein?
In the Journal of Scientific Food Agriculture, Jonker and colleagues wrote:
“In general, the nutritive value of proteins in foods is comparable, whether cooking is done by microwaves or conventional means…”
Cooking at high temperatures has potential to denature protein, but that’s an excess heat issue, not a microwave oven issue. The amount of denaturation depends on how long and at what temperature the food is cooked. Some of the more delicate biological subfractions could be damaged or destroyed in proteins like whey, but that doesn’t mean the protein quality or amino acids themselves are destroyed.
Related Note on Cooking Meat in a Microwave - Bacteria Concerns
Health alarmists often publish claims that deadly and dangerous bacteria can survive in foods cooked in a microwave oven. There have indeed been case studies published in medical journals about listeria, ecoli and salmonella. It can happen with any cooking method if the meat isn’t cooked completely.
Microwave ovens are used most often for reheating food, but some people use microwaves to cook raw meats. Because microwave ovens may heat food non-uniformly, if you try to you cook a whole, stuffed chicken in the microwave, some areas may not get cooked completely, so e.coli or listeria, if present, may not be destroyed.
If you don’t want to take any chances, don’t cook whole raw chickens in the microwave!
Also, lightly cooked eggs could harbor salmonella. Whether you’re using a microwave or a conventional stove top to cook eggs, make sure they’re fully cooked. Salmonella risk from eating raw eggs is very low, but eat them raw at your own risk. Also be careful of microwaved eggs as there is a potential for them to explode inside the microwave or outside, after you've removed them.
A Related Note on Non-uniform Cooking - Caution! Watch out for hot spots!
Have you ever noticed how some parts of your microwaved food are cooked thoroughly and others are still lukewarm or even cold? It can definitely be annoying, but experts have expressed a serious concern over the potential for burns in adults, children and infants because one portion of the food can be cool or warm and another scalding hot.
Microwave technology has improved over the years to help mitigate this “hot spot” problem (including rotating carousels), but non-uniform heating is always somewhat of an issue to be aware of when consuming food cooked with microwave ovens.
This problem is easily solved with a little common sense and caution. Just mix or stir your food, and let it stand briefly before eating it. Eat hot food with caution.
Myth 6: Microwaved Milk and Infant Formula is Dangerous
Anti microwave websites often mention that microwave-heated baby formulas and breast milk should not be fed to infants, based on potential damage to the milk itself or potential burn injuries.
One study from the Stanford University School of Medicine was published in the journal Pediatrics. They tested 22 human milk samples for lysozyme activity, total IgA, and specific secretory IgA to E coli by heating them by microwave at various low and high power settings. They concluded that microwaving appears to be contraindicated at high temperatures due to nutrient damage, and questioned microwave use even at lower temperatures.
The Stanford study is selectively quoted all the time by anti-microwave groups. What about the rest of the research? A study published in the International Journal of Food Science and Nutrition said, “microwave heating of human milk can be performed without significant losses of examined immunoglobulins and nutrients, provided the final temperatures are below 60 degrees C.”
Jonker from The Journal of ScientificFood Agrigulture:
“When the microwave treatment is well controlled to avoid overheating, such biological properties as the clotting activity of plasma and antibacterial activities are reasonably maintained.”
As I mentioned earlier, it appears that overheating any food with any cooking method could destroy a small portion of the nutrients, but it doesn’t make the food harmful to eat. As noted above, heating in a microwave does not create or add any toxic compounds to foods or drinks.
Related note about Super-heated liquids
Burns are a possible safety concern due to the uneven heating of food. There’s also a potential danger for anyone to get scalded due to overheated liquids (or steam).
In microwave ovens, the water can become super-heated past its boiling point and yet bubbles don’t form. When the liquid is disturbed or something is dropped in it, like sugar, the heat is released, and it’s possible for boiling water to bubble over and out of the container.
While water may not explode literally, microwave water or hot beverages can bubble over due to the super-heating phenomenon (water in a liquid state that is over 100 degrees Celsius).
Burns from liquids could happen to adults, children or infants from overheating or spills.
Of course, grown adults have been known to burn themselves in kitchen mishaps. Just don’t blame the microwave, just be careful of hot liquids because they burn.
Reality: Microwaves are Safe
As you can see, there are some legitimate microwave oven safety issues to be aware of, but they’re no different than basic cooking safety with any kind of conventional oven, stove top, grill or fire.
If you pay attention, you’ll notice that nearly all of the alarmist detractors are uncritical, propagandist coming from the “alternative health,” “natural health” or “raw foods” movements. Remember, some nutrients become more bio-available when cooked.
Some of the people and organizations who spread this misinformation are honest and sincerely believe in what they’re saying. But as physicist Robert Park wrote in Voodoo Science,
“What may begin as honest error has a way of evolving through almost imperceptible steps from self-delusion to fraud.”
True to that point, some are using scare tactics as tools for marketing or furthering their agendas.
I'll leave you with one more statement from Ashim Datta, a professor of biological and environmental engineering at Cornell University. He’s the author of numerous research papers, book chapters and books, including the Handbook of Microwave Technology for Food Applications. These are his thoughts of the microwave controversy:
“Based on my knowledge of the last 30-35 years of research literature on microwave heating, microwaves have only thermal effect, i.e., increase in temperature. There is no other “microwave” effect. Because microwaves heat non-uniformly, some places can heat a lot more and get charred and produce undesirable compounds. This, however, is just as true with any heating process, including hot air or grill. For the same reason of non-uniform heating, some locations in the food can heat a lot less and thus not destroy enough of pathogenic microorganisms (when this is an issue), causing a food safety problem, in much the same way as in conventional heating. Absolutely no negative health effects of microwave heating have been shown conclusively in all these years since microwave heating was started in the 50s.”
Let's finally close the case now on all the microwave oven alarmism and move on to the next health and fitness topic.
Until next time - ENVISION, BELIEVE, EXECUTE and SUCCEED
To your health!
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