Ask Natural Life...
How Safe and Healthy is
Microwave Cooking?
by Wendy Priesnitz
 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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