medicine physician who operIt all started with Hans Hertel.
ates what he says is the “#1
The Swiss food chemist andNatural Health Site” on theseven fellow vegetarians conInternet (www.mercola.com).
fined themselves to a hotel for
Foods cooked in microwave
two months in the late 1980s.
ovens are “a recipe for cancer,”
There, they consumed milk andadds medical journalist Simon
vegetables prepared in the microBest on his Electromagnetic
wave oven and in other ways.
Hazard and Therapy Web site
Hertel emerged with an aston(www.em-hazard-therapy.com).
ishing pronouncement. Eating
Hertel and Kopp aside, here’s
microwaved milk and vegetables
what we know about microcaused changes in the men’s
wave ovens.
blood that “appear to indicate
the initial stage of a pathological
Inside the Microwave
process such as occurs at the start
F
A
C
T
V
S.
F
I
C
T
I
O
N
of a cancerous condition.”“A microwave oven heats food
Hertel didn’t actually find thatusing radio waves that are
By David Schardt
microwaved food caused cancer.
almost identical to radar,” says
And his “study,” which no reJim Felton of the Lawrence
e are increasingly concerned about the damage
searchers have tried to reproduce,
Livermore Radiation Laborawas never peer-reviewed or pubtory in Livermore, California.
done to food in the home microwave oven,” thelished in a scientific journal.
The frequency used in micro“Without knowing more
wave ovens, about 2,500 megaeditor of an upstate New York newspaper e-mailed Nutrition
about how he conducted his
hertz (MHz), is more powerful
Action Healthletter last November.
study, what he measured, how hethan the frequency that’s usedmeasured it, and what he found,to transmit radio, television,“According to the sources we find online and elsewhere,
it’s impossible to even begin toand cell phone signals. But it’sevaluate his findings,” says Barry
thousands of times weakermicrowaving food creates carcinogens, and in parts ofSwanson, a food scientist atthan ultraviolet light, visible
Europe, health authorities have banned microwaves as danWashington State University inlight, and X-rays and millions
Pullman.
of times weaker than the
gerous to human health.”
Hertel has dropped out of pubgamma radiation that’s used tolic view. So has William Kopp,
It’s not clear why so many people are uneasy about microirradiate some foods.
described only as a “U.S. re“While X-rays, gamma radiawave ovens. “Maybe it’s because there’s no obvious reason
searcher,” who wrote an article intion [though not irradiated1996 claiming that Cold Warfood], and even sunlight can
why the food cooks,” offers physicist Louis Bloomfield of theresearch in the Soviet Union had
cause cancer, microwave radiaUniversity of Virginia in Charlottesville, who answers quesproven the dangers of microwave
tion cannot because it simply
ovens.
doesn’t pack enough power totions about microwaves at howthingswork.virginia.edu.
“People who ingested microdamage your DNA,” says Gary
waved foods showed a statistiZeman of the Health Physics
And those questions are becoming more urgent, ascally higher incidence of stomSociety in McLean, Virginia.
charges and rumors speed across the Internet. Here’s how
ach and intestinal cancers, plus a
The Society is a nonprofit scigeneral degeneration of periphentific organization that proto separate microwave fact from fiction.
eral cellular tissues and a gradualmotes radiation safety.
breakdown of the function of theWhat 2,500 MHz microdigestive and excretory systems,” Kopp
waves can do is get absorbed by the water,ished, believing that the appliance induswrote.
fats, and sugars in food. That generates
try was out to persecute him.
The Soviet research was never pubheat, which cooks the food. Once theWhile Hertel and Kopp are no longer
lished and the institute where it was conoven is turned off, it produces no morearound, their unsubstantiated charges areducted, in what is now the Republic of
microwaves. And those that it did proall over the Internet.
Belarus, no longer exists. (The former
duce are long gone.
“The prolonged eating of microwaved
Soviet Union may have banned micro“The lifetime of microwaves in the
foods causes cancerous cells to increase inwave ovens for a short period, but nooven is something like millionths of ahuman blood,” says “10 Reasons to Throw
countries ban them today.) Kopp himself
second,” says physicist Louis Bloomfield.
Out your Microwave Oven,” an article byreportedly changed his name and vanJoseph Mercola, an Illinois alternative-

W

Illustrations: Loel Barr.

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CancerForget the charges floating around theInternet. The “evidence” that microwaved foods cause cancer boils down toHans Hertel’s and William Kopp’s claims.
“There is nothing solid,” says Lawrence
Livermore’s Jim Felton, who is also associate director for cancer control at theCancer Center at the University of California, Davis.
That may explain why scientists
haven’t spent time and money looking
for a link. “I can honestly tell you that I
have never seen a valid scientific study—
and I pay attention to most of the cooking research out there—that has given us
reason to test

F E A T U R E

whether microwaving food could cause
cancer,” says Felton.
“In fact, my research suggests just the
opposite.”
Grilling or frying meat and poultry cancreate heterocyclic amines, which may
cause cancer. When Felton and his colleagues briefly microwaved meats anddrained off the juices before grilling, mostof the precursors of those potential carcinogens were lost along with the juices.1“I generally recommend that patients
microwave their meats for one to fiveminutes and discard the juices before
grilling,” says researcher Cyndi Thomsonof the Arizona Cancer Center at the University of Arizona in Tucson.

Nutrients
If you microwave your food, “you’re zapping away nutrients and risking yourhealth,” charges physician Joseph Mercola, who recommends that consumers
get rid of their microwave ovens and eat
at least a third of their food raw.
“Actually, microwaving retains more
nutrients than other forms of cooking, if
you don’t use a lot of water and don’t
overcook the food,” says food scientist
Barry Swanson.
“For some reason, people think heatbreaks down vitamins, but most vitamins
are really very stable to heat. Nutrientsare mostly lost into the water, and there’s››››

Safe Microwaving
Cooking & Reheating Arrange food evenly in the dishand add some liquid if needed.
Cover with a loose lid to let any steam
escape. (If you use plastic wrap, make sure it doesn’t come incontact with the food.)
 Don’t cook large cuts of meat on high power (100%). Use
medium power (50%) and a longer cooking time, so the heatcan reach the center without overcooking the outer areas.
 If your microwave doesn’t have a carousel, stir or rotate thefood midway through the microwaving time.
 If you’re partially cooking food in the microwave before you
finish it on the grill or in a conventional oven, transfer the microwaved food immediately. Warm, partially cooked food is abreeding ground for bacteria.
 Use a food thermometer or the oven’s temperature probe toverify that meat, poultry, and casseroles have reached a safe
temperature. Place the thermometer in the thickest area of themeat or poultry—not near fat or bone—and in the innermost partof the thigh of whole poultry. Check in several places to be sure
red meat reaches 160° F, poultry reaches 180° F, and egg
casseroles reach 160° F. Fish should flake with a fork. Leftovers
should reach 165° F.
 Food continues to cook after the microwave is turned off, asheat flows from hotter to cooler regions. So allow dense foods
like meat, poultry, quiche, and casseroles to stand for five minutes before you check the internal temperature. Foods thataren’t dense—cut vegetables, bread, soup, and beverages, forexample—don’t need to stand.
 Don’t cook whole, stuffed poultry in the microwave. The stuffing might not reach the temperature needed to destroy harmful
bacteria.

 Heat ready-to-eat foods like hot dogs, fully cooked ham, andleftovers until they’re steaming hot.

Defrosting Remove food from its packaging before you defrost it in the
microwave. Foam trays and plastic wraps can melt, which cancause potentially harmful chemicals to migrate into the food.
 If you’ve defrosted meat, poultry, egg casseroles, or fish in
the microwave, cook it immediately.

Cookware, Containers, & Wraps
 The containers you use for cooking and reheating should belabeled “microwave safe.” Thick, non-decorative glass is alsosafe.
 “No way should you cook or reheat food in a yogurt,
margarine, or dessert topping tub,” says the FDA’s Kristina
Paquette, “because they haven’t been tested or approved.”
They can warp or melt, which can cause chemicals—like theplasticizers that make the containers flexible—to migrate into
the food.
 It’s okay to use wax paper, cooking bags, parchment paper,
microwave-safe paper plates, and white microwave-safe paper
towels (the dyes used in non-white paper towels haven’t been
approved for use with food in the microwave).
 Never use thin plastic storage or grocery bags (they canmelt), brown paper bags or newspaper (both sometimes containbits of metal and the bags’ seams could contain glue), or
aluminum foil (it can cause dangerous arcing).
Source: Adapted from U.S. Department of Agriculture(www.fsis.usda.gov/factsheets/cooking_safely_in_the_microwave/index.asp).

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no reason to add water to vegetables oranything else that already contains a lotof water.”Too much water was apparently the
problem in a 2003 study in which European researchers reported that microwaving broccoli in a bowl of water destroyed
nearly all of several flavonoids, whilesteaming had only a mild effect onthem.2 (Flavonoids are plant compounds
that may help protect against heart disease and cancer, though the evidence isscanty.)That research isn’t relevant to household microwaving, says Swanson. “Basically, the researchers added far too muchwater and microwaved the living daylights out of the broccoli.”

Wraps, Containers,& Packaging
How safe are plastic wraps, frozen-foodtrays, and “microwave-safe” containers
and packaging?
 Plastic wrap. E-mails widely circulating around the Internet warn that plastic
wraps release the carcinogen dioxin
when microwaved.
“It’s a chemical impossibility because
the precursors for dioxin are not in theplastic wrap,” says George Sadler, a professor of food packaging at the National
Center for Food Safety and Technology in
Summit, Illinois. The center is a consortium of scientists from academia, theFood and Drug Administration, and thefood industry.
“We are not aware of any plastics thatyield dioxin as a breakdown product,absolutely none,” adds Kristina Paquetteof the FDA’s Office of Food Additive
Safety in College Park, Maryland.
“I’ve seen another e-mail recently warning against using plastic wrap because of
the phthalates it supposedly produces,”says Sadler. (Phthalates make plastic flexible.) “Manufacturers quit using thosemany, many years ago.”
While plastic food wrap hasn’t been
approved by the FDA for use in microwave ovens, says
Paquette, “aslong as thewrap doesn’ttouch thefood whileit’s cooking,there’s little
chance of12

F E A T U R E

any chemicals migrating from the wrap
into the food.”
Besides, she notes, “there are no components of plastic wrap that are considered carcinogenic in humans.”
 Containers & packaging. “If it’s
food you buy in a store for microwaving,
like a frozen dinner, I would be 100 percent confident in using the container itcame in,” says Paquette. “But remember,
those are usually approved for only one
use, because the polymer in the packaging can start to break down during a second use in the microwave.”“The FDA has a rigorous protocol that
manufacturers of food packaging must
execute every time they have new packaging components they want to use,” says
George Sadler. “Companies must measure how much, if any, of the packaging
materials migrate into the food whenthey’re heated in the microwave. Thenthe manufacturer has to undertake a rigorous toxicological evaluation to showthat those levels are safe.”(“Safe” means that any packaging
material that ends up in the food is at lessthan one-hundredth the lowest level thatcauses harm in animal studies.) The company has to test for cancer, genetic damage, and any impact on reproduction ordevelopment.
“The FDA’s testing guidelines for
microwave containers pretty much cover
the gamut of anything anyone would dowith something in a microwave,” adds
Paquette, “because everybody wants tomake sure they have a cushion of safety
there.”Do those safeguards extend to reuseable plastic containers you buy at thesupermarket? Yes, as long as they say“microwave safe,” which means they’vebeen tested for up to 240 hours in the
microwave. (While other containers
might be as safe, their components
haven’t been tested.)

NUTRITION ACTION HEALTHLETTER  A P R I L 2 0 0 5

 Heat susceptors. Ever
wonder why microwave
popcorn bags are clearlymarked “This Side Up”
or “This Side Down”?
The bottom of the
package contains a
metallicized surface
that absorbs microwaves and becomes

hot enough to pop the popcorn.
Can that “heat susceptor” generateenough heat to trigger the release ofchemicals like packaging adhesives into
the food? No, says the FDA’s Paquette.
“If you look in a popcorn bag, you
don’t actually see the silver-colored heatsusceptor,” she explains. “It’s sealed
inside a pouch in the bag itself.” That
helps to dramatically reduce the migration of chemicals into the popcorn oil,says Paquette.

Radiation Leaks
Do microwave ovens leak radiation?
“The FDA discontinued field testingthem in the early 1980s, in part becauseof budget cutbacks and in part because
few ovens didn’t meet federal safety standards,” says George Kraus of the agency’s
Center for Devices and Radiological
Health.
In 2000, Health Canada (the Canadianequivalent of the Department of Healthand Human Services) tested 60 new
microwave ovens and 103 used ovens.
None of the new ones, and only one of
the used ones, exceeded Canada’s stringent leakage limits, which are similar to
the U.S. limits. The one oven that failed
was 23 years old.
“Leakage of microwaves can only occur
if the cooking chamber—including themetal grid over the front window and theseals around the door—has holes in it,”says the University of Virginia’s Louis
Bloomfield.
And even in the unlikely event thatyour microwave does leak, you’re notgoing to be showered with radiation.
Microwaves lose intensity rapidly as they
spread out. By the time they’ve traveled afoot or so from a small leak, they’ve effectively disappeared.
1
2

Food Chem. Toxicol. 32: 897, 1994.
J. Science Food Agric. 83: 1511, 2003.