Fact vs. fiction

Nutrition Action Healthletter, April, 2005 by David Schardt

"We are increasingly concerned about the damage done to food in the home microwave oven," the editor of an upstate New York newspaper e-mailed Nutrition Action Healthletter last November.

"According to the sources we find online and elsewhere, microwaving food creates carcinogens, and in parts of Europe, health authorities have banned microwaves as dangerous to human health."

It's not clear why so many people are uneasy about microwave ovens. "Maybe it's because there's no obvious reason why the food cooks," offers physicist Louis Bloomfield of the University of Virginia in Charlottesville, who answers questions about microwaves at howthingswork.virginia.edu.

And those questions are becoming more urgent, as charges and rumors speed across the Internet. Here's how to separate microwave fact from fiction.

It all started with Hans Hertel.

The Swiss food chemist and seven fellow vegetarians confined themselves to a hotel for two months in the late 1980s. There, they consumed milk and vegetables prepared in the microwave oven and in other ways.

Hertel emerged with an astonishing pronouncement. Eating microwaved milk and vegetables caused changes in the men's blood that "appear to indicate the initial stage of a pathological process such as occurs at the start of a cancerous condition."

Hertel didn't actually find that microwaved food caused cancer. And his "study," which no researchers have tried to reproduce, was never peer-reviewed of published in a scientific journal.

"Without knowing more about how he conducted his study, what he measured, how he measured it, and what he found, it's impossible to even begin to evaluate his findings," says Barry Swanson, a food scientist at Washington State University in Pullman.

Hertel has dropped out of public view. So has William Kopp, described only as a "U.S. researcher," who wrote an article in 1996 claiming that Cold War research in the Soviet Union had proven the dangers of microwave ovens.

"People who ingested microwaved foods showed a statistically higher incidence of stomach and intestinal cancers, plus a general degeneration of peripheral cellular tissues and a gradual breakdown of the function of the digestive and excretory systems," Kopp wrote.

The Soviet research was never published and the institute where it was conducted, in what is now the Republic of Belarus, no longer exists. (The former Soviet Union may have banned microwave ovens for a short period, but no countries ban them today.) Kopp himself reportedly changed his name and vanished, believing that the appliance industry was out to persecute him.

While Hertel and Kopp are no longer around, their unsubstantiated charges are all over the Internet.

"The prolonged eating of microwaved foods causes cancerous cells to increase in human blood," says "10 Reasons to Throw Out your Microwave Oven," an article by Joseph Mercola, an Illinois alternative-medicine physician who operates what he says is the "#1 Natural Health Site" on the Internet (www.mercola.com).

Foods cooked in microwave ovens are "a recipe for cancer," adds medical journalist Simon Best on his Electromagnetic Hazard and Therapy Web site (www.em-hazard-therapy.com).

Hertel and Kopp aside, here's what we know about microwave ovens.

Inside the Microwave

"A microwave oven heats food using radio waves that are almost identical to radar," says Jim Felton of the Lawrence Livermore Radiation Laboratory in Livermore, California.

The frequency used in microwave ovens, about 2,500 megahertz (MHz), is more powerful than the frequency that's used to transmit radio, television, and cell phone signals. But it's thousands of times weaker than ultraviolet light, visible light, and X-rays and millions of times weaker than the gamma radiation that's used to irradiate some foods.

"While X-rays, gamma radiation [though not irradiated food], and even sunlight can cause cancer, microwave radiation cannot because it simply doesn't pack enough power to damage your DNA," says Gary Zeman of the Health Physics Society in McLean, Virginia. The Society is a nonprofit scientific organization that promotes radiation safety.

What 2,500 MHz microwaves can do is get absorbed by the water, fats, and sugars in food. That generates heat, which cooks the food. Once the oven is turned off, it produces no more microwaves. And those that it did produce are long gone.

"The lifetime of microwaves in the oven is something like millionths of a second," says physicist Louis Bloomfield.

Cancer

Forget the charges floating around the Internet. The "evidence" that microwaved foods cause cancer boils down to Hans 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 the Cancer 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 whether microwaving food could cause cancer," says Felton.