The Microwave: A Friend or Foe in the Kitchen by Jessica Wong
After coming home from a long day at work or school, many people turn to the microwave as a way to save time in the kitchen. The speed and ease of heating food with a microwave remains unrivaled by any other method. However, some websites and research do indicate that using the microwave may be the wrong choice. But before we make a choice, we need to know what distinguishes the microwave from other cooking devices and what happens to the condition of microwaved food?
How Microwaves Work Inside microwaves, there is a magnetron that produces microwavelength radiation at about 2.45 gigahertz. Micro-waves heat food via two concurrent mechanisms, dipolar polarization and ionic conduction. Molecular dipoles align with the external electric fields by rotation. With exposure to micro-waves, and, an oscillating electric field, the molecular dipoles in the food oscillate and create heat through molecular friction and collisions. In contrast, ionic conduction involves the electrical field from micro-waves; ions in the food move towards like charges, which also increases the rate of molecular collisions and heat generation .
Heat Spots in Microwaved Food In comparison to a conventional oven, which heats food by heating the surrounding air, the heating of food in a microwave is caused by the previously described alternating electromagnetic field. Because the electromagnetic field from the micro-waves is not distributed evenly in the microwave, the food is heated unevenly. The uneven heating is also due to the differences in the characteristics of the microwaved food including quantity and composition. For example, food with higher water or salt content would have greater heating at the surface because they absorb more microwaves while decreasing the depth of penetration of microwaves. This leads to the formation of hot and cold spots in microwaved foods, which brings up concerns regarding microbiological food safety issues. However, this can be resolved by mixing the food during the microwaving process and letting the food sit after microwaving to allow the heat to distribute evenly .
What does Microwaving do to what is Microwaved? In Oklahoma, there was a 1991 lawsuit for medical malpractice because a hospital administered microwaved blood for blood transfusion and consequently killed the patient. Typically, transfusion blood is heated using other methods and thus, the microwave may have altered the blood in some way different from traditional heating methods. This lawsuit has caused much concern regarding the use of microwaves. If the microwave altered the blood of this patient, it could potentially be altering the food we microwave. However, the convenience of the microwave has led to its increased usage to warm food throughout the years. . Dr. Hans Ulrich Hertel was one of the first scientists who studied the effects of consuming microwaved food on consumers, using milk and vegetables as test materials. These consumers were given the same milk raw, conventionally cooked, pasteurized and microwaved at separate intervals. They were also given the same fresh vegetables raw, conventionally cooked, defrosted in a microwave and cooked in a microwave at separate intervals. Before and after these foods were consumed, blood samples of the consumers were taken to monitor any changes. Monitoring levels of hemoglobin and cholesterol in the blood showed a decrease in both after the consumers ate the microwaved food. There was also an observed increase in the number of leukocytes, or white blood cells, which is often a sign of damage to the body. This occured only after the consumption of the microwaved food .
Micro-wave Leakage from Microwaves There has also been concern as to whether microwaves leak micro-waves and if the amount leaked is harmful to humans The Food and Drug Administration (FDA) limits the amount of micro-wave leakage from microwaves throughout its lifetime to five milliwatts (mW) of microwave radiation per square centimeter at two inches from the surface. As you move away from the microwave, the amount of micro-waves from leakage decreases dramatically. There is also a required lock system to stop the production of micro-waves when the door of the microwave is opened. However, there has been little research on long-term exposure to these levels of micro-wave radiation on humans. Research on micro-wave exposure in mice has been performed but it is not certain how this would relate to micro-wave exposure to humans . The limited research that has been performed has shock the public. The symptoms of micro-wave exposure include fatigue, headaches, palpitations, insomnia, skin symptoms, impotence and altered blood pressure. All of these symptoms and have been termed ‘microwave sickness’. In one such study, Sadcikova of the Academy of Medical Sciences studied two groups of people who worked with micro-waves of a frequency in the gigahertz range. One group of 1000 workers was exposed to a ‘few mW/cm2’ and another group of 180 workers experienced exposures of no more than several hundredths of a mW/cm2. A control group of 200 workers with no micro-wave exposure was included as well. The three main symptoms present were neurological (tiredness, irritability, sleepiness and partial loss of memory), autonomic vascular changes (sweating, dermographism, blood pressure changes), and cardiac changes. Tiredness affected forty-five percent of those exposed to a few mW/cm2, fifty-five percent of those exposed to several hundredths of a mW/cm2 and only ten percent of the control group. There was not a large difference between the two levels of exposure but those with over five years of exposure had more symptoms than those with less than five years of exposure . In a separate study performed in La Nora, Murcia, Spain, exposure to wavelengths between 400MHz – 3 GHz and a power level of 1uW/m2 was examined. After adjusting for sex, age and distance from the source of the radiation, researchers found a statistically significant positive dose – response association with fatigue, irritability, headaches, nausea, loss of appetite, sleeping disorder, depressive tendency, feeling of discomfort, difficulty in concentration, loss of memory, visual disorder, dizziness and cardiovascular problems . Another research study performed in Russia gave similar results but also observed an increased rate of cancer cell formation in the blood as well as an increased rate of stomach and intestinal cancers and increased rates of digestive disorders .
What can we do? There have been few studies on the effects of eating microwaved foods for humans and whether microwaves emitted at this level can be harmful in the long run. To do such research is difficult because it requires long-term isolation of the cause of microwave-sickness symptoms. Studies on the chronic effects of micro-wave emissions are rare because it is less ethical to test human subjects and so the only research is that which can be observed. Due to this limitation, there have been few public warnings and many people have been accustomed to the use of a convenient microwave in their daily lives. Until more studies are completed to solidify the existing research on microwaved foods and micro-wave leakage, using other methods to cook food may be resorted to for the time being.
Jessica Wong is an undergraduate at Carnegie Mellon University.
1. How Microwaves Work. Biotage. 2008. http://www.biotage.com/DynPage.
aspx?id=22053. Date Accessed: 12/21/09.
2. Fundamentals of Microwave Technology. Charm Bioengineering. 1999. http://
www.utherm.com/html/microwave.htm. Date Accessed: 12/21/09.
3. Interaction of Microwave Irradiation with Material. MicrowaveTec. 2009. http://
www.microwavetec.com/theor_basics.php. Date Accessed: 12/21/09.
4. Microwave Cooking and Food Safety. Food and Environmental Hygiene
Department. 2005. http://www.cfs.gov.hk/english/programme/programme_rafs/
files/microwave_ra_e.pdf. Date Accessed: 12/21/09.
5. Warner V. Hillcrest Medical Center. FindLaw. 1996. http://caselaw.lp.findlaw.
Date Accessed: 12/21/09.
6. Wayne, Anthony and Lawrence Newell. The Hidden Hazards of Microwave
Cooking. 2001. http://www.vsan.org/rok-az/misc/HazardsOfMicrowaveCooking.
pdf. Date Accessed: 12/21/09.
7. Microwave Oven Radiation. FDA. 2009. http://www.fda.gov/Radiation-
ucm142616.htm#4. Date Accessed: 12/21/09.
8. Hocking, B. Microwave Sickness: A Reappraisal. Oxford Journals. 2000. http://
occmed.oxfordjournals.org/cgi/reprint/51/1/66. Date Accessed: 12/21/09.
9. Gerd, Oberfeld. The Microwave Syndrome – Further Aspects of a Spanish Study.
http://avaate.org/IMG/pdf/Proceedings_Kos_2004.pdf. Date Accessed: 12/21/09.
10. Becker, Robert. The Body Electric. 1998. p314.