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How Safe and Healthy is Microwave Cooking?
by Wendy Priesnitz

question: how safe is microwave cooking.Q: I’d appreciate having your view on microwave cooking. Is it safe, and just a different form of cooking? Some time back, I read an article that caused me to get rid of my microwave as it stated it affected nutrients in food.

A: Microwave ovens, their safety, and their effect on the nutritional value of food is yet another subject that yields wildly conflicting and sometimes alarmist information.

The microwave oven generates electromagnetic waves (called microwaves because they’re short) at a frequency of 2450 megahertz (FM radio waves are generated at around 100 MHz and cell phones transmit 800 MHz). The microwaves bombard the molecules of water in the food. These molecules each have a positive and negative end, or “polarity.” The polarized molecules try to line themselves up with the electrical field, like compass needles trying to point North. But because the electrical field is reversing polarity at a rate of 2,450 million cycles a second, the water molecules end up rotating at the same speed. That activity generates heat, which cooks the food, literally from inside out, as opposed to other types of cooking, which transfer heat convectionally from the outside in. This process is a form of non-ionizing radiation, which is different from the more harmful radiation associated with x-rays, UV light, and atomic bombs.

While microwaves don't make food radioactive or change the structure of atoms, the level of movement of molecules required to create sufficient heat to cook food is thought by some researchers to cause damage to food. 

However, conventional government and medical wisdom (often funded and/or encouraged by corporate interests) is reassuring and tends to portray concerns about the health effects of microwaves on food as alarmist and pseudoscientific, in spite of little scientific research disproving them. So it is difficult to figure out exactly where the truth lies. And in such cases, I suggest precaution.

For instance, Food Science Australia, a government and industry-funded company whose mission is to “help make Australian food companies among the most competitive in the world,” has dismissed consumer concerns about microwave cooking as having been fueled by media coverage of isolated and irrelevant reports. The Food and Drug Administration in the U.S. simplistically states that “foods cooked in a microwave oven may keep more of their vitamins and minerals, because microwave ovens can cook more quickly and without adding water.”

That latter statement is disproved by a Spanish study published in the Journal of the Science of Food and Agriculture in 2003. Researchers from the Spanish scientific research council CEBAS-CSIC found that cooking by microwave is the worst way to preserve at least one key nutrient in vegetables. According to Dr. Cristina Garcia-Viguera, co-author of the study, microwaved broccoli loses 97 percent, 74 percent, and 87 percent of the three major cancer-protecting antioxidant compounds (flavonoids, sinapics, and caffeoyl-quinic derivatives). By comparison, steamed broccoli loses 11 percent, 0 percent, and 8 percent of the very same antioxidants.

In a 1992 article in the journal Pediatrics, a team of researchers from Stanford University reported that re-heating human breast milk in a microwave oven – even at a low setting – can destroy some of its important disease-fighting capabilities. Specifically, it lost lysozyme, which protects against bacterial infection. The fact that adverse changes were found at very low temperatures suggested to the researchers that “microwaving itself may in fact cause some injury to the milk above and beyond the heating.”

Vitamin B-12 is another nutrient that can be destroyed by microwaving. Japanese research reported in Science News in 1998 found that as little as six minutes of microwave cooking destroyed half of the vitamin B-12 in dairy foods and meat, a much higher rate of destruction than other cooking techniques.

Microwaving baby formula is also a problem, according to Dr. Lita Lee of Hawaii in the Lancet medical journal in 1989. She wrote that microwaving baby formula converts certain trans-amino acids into synthetic substances like trans-fatty acids. Further, one of the amino acids, L-proline, converts to a substance known to be poisonous to the nervous system and to the kidneys.

Without a doubt, any type of cooking or reheating of food will destroy nutrients in food; exposing enzymes and protein, for instance, to high heat will alter them.

Early Research

Some of the earliest research into the effects of microwaved food was conducted in the 1950s in Russia. That research indicated bigger dangers than destruction of nutrients. Russian researchers found that people who ate microwaved foods had a statistically higher incidence of stomach and intestinal cancers, a general degeneration of peripheral cellular tissues, and a gradual breakdown of the digestive and excretory systems. Due to chemical alterations within the food, they had lymphatic malfunctions, causing a degeneration of the body’s immune system. For instance, microwaving milk and cereal grains converted some of their amino acids into carcinogens, thawing frozen fruits converted their glucoside and galactoside containing fractions into carcinogenic substances, and carcinogenic free radicals were formed in microwaved plants, especially root vegetables. They also reported structural degradation leading to decreased availability of Vitamins B, C, E and essential minerals at a rate of 60 to 90 percent in all foods tested.

As a result of that research, the Soviets banned the use of microwave ovens in 1976 and issued an international warning on the health hazards, both biological and environmental, of microwave ovens and similar frequency electronic devices. The ban has since been over-turned and the rest of the world appears not to have headed the warning.

In 1989, the Swiss food scientist Dr. Dans Ulrich Hertel fed eight volunteers a range of raw, conventionally cooked and microwaved food. Blood samples, taken from each person after eating, showed serious irregularities in the structure of the food microwaved, and in the blood of those eating the microwaved samples. These changes included a decrease in all hemoglobin and cholesterol values, especially the ratio of HDL (good cholesterol) and LDL (bad cholesterol) values. Lymphocytes (white blood cells) showed a more distinct short-term decrease following the intake of microwaved food than after the intake of all the other variants.

In 1991, he and Dr. Bernard H. Blanc of the Swiss Federal Institute of Technology and the University Institute for Biochemistry published a research paper indicating that food cooked in microwave ovens could pose a greater risk to health than food cooked by conventional means. An article also appeared a Swiss environmental magazine entitled Journal Franz Weber, which stated that the consumption of food cooked in microwave ovens had cancerous effects on the blood as indicated by an increase of leukocytes, which could indicate cell damage, after eating microwaved substances. As soon as Doctors Hertel and Blanc published their results, the authorities reacted. In 1992, a powerful trade organization, the Swiss Association of Dealers for Electro-apparatuses for Households and Industry, known as FEA forced the Swiss courts to issue a “gag order” against them. The following year, Dr. Hertel was convicted for “interfering with commerce” and prohibited from further publishing his results. However, he fought the decision and both it and the gag order were reversed in 1998 when the European Court of Human Rights in Austria ruled that there had been a violation of his rights in the 1993 decision. In addition, Switzerland was ordered to pay him compensation.

Other Potential Problems

Other potential problems with microwave cooking include radiation leaks from damaged door seals (although, remember that we are talking about non-ionizing radiation) and the leaching of chemicals from plastic containers or food wrap. The Center for Science in the Public Interest has expressed concerns about the leaching of hormone-disrupting plasticizers (chemicals used to make plastic more flexible), polyvinyl chloride, and polycarbonate in microwave ovens.

Health writer Dr. Andrew Weil has suggested that reheating foods in a microwave oven may not be harmful. However, according to the American Journal of Epidemiology, an outbreak of Salmonella typhimurium in Alaska was traced to food taken home from restaurants. While 30 people had taken home “doggie bags” only ten became sick; they had reheated their food in a microwave oven, while those who used a conventional oven or frying pan did not get sick. One of the issues involved with that problem could be the risk of uneven cooking or reheating when using microwaves, which results in both hot spots and areas of the food that haven't been heated enough.

There is clearly a need for more research, but North American universities and governments seem more interested in what happens if a microwave oven door malfunctions than on the effects of eating microwaved foods. Is it because the companies that fund much of the research don’t want us to know? 

Wendy Priesnitz is the Editor of Natural Life Magazine and a journalist with over 40 years of experience. She has also authored 13 books.


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