Microwave Ovens: What Do We Really Know?

By Jodi Friedlander, NC Curriculum Consultant, Bauman College

The subject of the safety of microwave oven use can cause heated debate. It seems that most people I speak with in the holistic nutrition field decry the use of these ovens, citing studies and articles that support their contentions that microwave cooking destroys nutrients and is dangerous to our health. The “studies” that virtually every book and Internet site use to condemn cooking in microwave ovens emanate from two sources that for all intents and purposes don’t exist.

One is early microwave oven research by a Swiss scientist named Hans Hertel, who found negative changes in the blood of people who ate microwave-cooked food. This study has never actually been seen by anybody, as far as can be ascertained through searches on the Internet, and according to some, it was neither peer reviewed nor published. Though it is not available anywhere for scrutiny, its “information” is widely reproduced, all based solely on hearsay. The second study has to do with alleged Russian research originating right after World War II and culminating, in 1976, with the banning of microwave ovens because of their supposed dangers. Not only is this particular study also unavailable for viewing, the author has purportedly changed his name and disappeared. Not only are microwave ovens currently in use everywhere in Russia, it appears that they were never banned.

There is considerable research available now (2013) on foods cooked in microwaves. The studies with findings that indicate large losses of nutrients tend to be older ones, where in review, researchers were found to have used large amounts of water and to have cooked study foods to death (think science nerds in white coats with little to no cooking expertise). Nutrients are lost in water, no matter the cooking method, the more water and the longer the cooking time, the greater the nutrient loss. Other studies, more rigorously controlled (no overcooking), are often finding FEWER nutrient losses all the way around from microwave cooking versus steaming (we’re talking mainly vegetables here, most often cruciferous). Another benefit is that there are no heterocyclic amines (carcinogens) in microwaved meats versus those cooked directly on heat sources, such as through barbequing, broiling, or pan-frying. An exception to lower nutrient loss has been shown to occur with beneficial bacteria, which may undergo more extensive destruction due to the inside-out nature of this cooking method, which often results in regionally very high temperatures. On the other hand, pathogenic bacteria have been found to be inadequately heated in some instances, causing outbreaks of illness. These both, however, are functions of temperature and cooking time, not of microwave cooking specifically. Clearly, we now know that unhealthful effects can be created when foods are microwave cooked or heated in materials that can leach toxins, such as plastics, but this can also occur from cooking in non-stick cookware on a stovetop.

Microwave ovens are also not dangerous to use. Their “radiation” is not high frequency; it is somewhere in the range of AM radio frequencies, and cordless and cellular phones, and these waves are easier to avoid than those from telephones and cell towers. As such, there are also no radiolytic or radioactive compounds released into food, as the ovens produce neither of these substances. And the doors of microwave ovens let almost none of their waves escape, anyway. Standing just 20 inches from a newer microwave oven prevents any effects. This has been well studied, is federally regulated, and a search on Google Scholar will turn up some high quality studies documenting this.

So, are microwave ovens just fine to use? I’d say they may serve us well for quick reheats of previously cooked foods, but as a tool for cooking, something crucial is missing, especially if that “cooking” is the heating of a packaged, processed food product. As humans, we have traditionally cooked with fire, whether over an open wood or stove fire, or with gas. Even electric cooktops and ovens deliver a similar cooking experience. I see this kind of cooking as a primary spiritual connection with our food. Stirring food over an open flame, or opening a hot oven to look at something baking or roasting, evokes satisfaction and deep emotion in many of us. It draws people together, creating an easy avenue of social connection, that all-important aspect of healthy living. My sense is that microwaving separates us even further from our food supply, disconnects us from what is not only the physical act of nourishing ourselves, but from a deep, spiritual connection to our food, from which we’re already too distanced. Most people don’t grow anything they eat; they have no idea where their plant foods come from or how their dairy and meat animals are raised (or tortured, depending on their source). Many people think food comes from the supermarket – in boxes or bags – and that cooking occurs not in pots and pans but from pushing buttons on a small box. That is a bleak prospect and represents to me the true downside of microwave cooking. Nonetheless, it is vitally important to have facts to counter urban myths, and current research has demonstrated that consuming microwave-cooked food appears to be quite safe when proper temperatures, cooking times, and procedures are utilized.  So, whether we like it or not, as our forefather James Adams said, “Facts are stubborn things; and whatever may be our wishes, our inclinations, or the dictates of our passion, they cannot alter the state of facts and evidence.” At least not until the next round of research.

SOURCES

Galgano, F., Favati, F., Caruso, M., Pietrafesa, A., & Natella, S. (2007, Mar). The influence of processing and preservation on the retention of health-promoting compounds in broccoli [Abstract]. J Food Sci, 72(2):S130-5. PMID:17995854

Hearn, T., Sgoutas, S. and Sgoutas, D. (1987). Stability of polyunsaturated fatty acids after microwave cooking of fish [Abstract]. Journal of Food Science, 52(5):1430-1431. doi: 10.1111/j.1365-2621.1987.tb14100.x

International Microwave Power Institute’s Forum for Microwave Technology Discussion (IMPIORG). (2012, Jun 13). Did Russia ban microwave ovens at some point in the past? Retrieved from http://impiorg.wordpress.com/2012/06/13/did-russia-ban-microwave-ovens-at-some-point-in-the-past/

Jiménez-Monreal, A.M., García-Diz, L., Martínez-Tomé, M., Mariscal, M., & Murcia, M. A. (2009). Influence of cooking methods on antioxidant activity of vegetables [PDF]. Journal of Food Science, 74(3):H97-H103. doi: 10.1111/j.1750-3841.2009.01091.x

López-Berenguer, C., Carvajal, M., Moreno, D.A., & García-Viguera, C. (2007, Nov 28).  Effects of microwave cooking conditions on bioactive compounds present in broccoli inflorescences [Abstract]. J Agric Food Chem, 55(24):10001-7. Epub 2007 Nov 3. PMID:17979232

Love, J.A. & Prusa, K.J. (1992, Nov). Nutrient composition and sensory attributes of cooked ground beef: Effects of fat content, cooking method, and water rinsing [Abstract]. J Am Diet Assoc, 92(11):1367-71. PMID:1430722

Pellegrini, N., Chiavaro, E., Gardana, C., Mazzeo, T., Contino, D., Gallo, M.,…Porrini, M., (2008). Effect of different cooking methods on color, phytochemical concentration, and antioxidant capacity of raw and frozen Brassica vegetables [Abstract]. J. Agric. Food Chem, 58(7):4310–4321. doi: 10.1021/jf904306r

Tajchakavit, S., Ramaswamy, H. S., & Fustier, P. (1998, Dec). Enhanced destruction of spoilage microorganisms in apple juice during continuous flow microwave heating [Abstract]. Food Research International, 31(10):713-722. http://dx.doi.org/10.1016/S0963-9969(99)00050-2

Xu, J., Wei, J., Guo, C., & Yang, J. (2007, Mar). [Effect of various cooking methods on the contents of major flavonoids in vegetables]. [Article in Chinese]. Wei Sheng Yan Jiu, 36(2):223-5. PMID:17555108

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