Dr. John Weisburger, senior member of the American Health Foundation and professor of pathology at New York Medical Colege, replies:

It’s hard to say when you’re overcooking. Because it’s not really overcooking—it’s just cooking the usual way. Creatinine, a component of muscle meat derived from pork or beef or fish, reacts during heating with sugars and amino acids to form hetrerocyclic amines. So standard cooking makes heterocyclic amines. The more cooked the burger is, the more of these amines are formed. Epidemiology has shown that these amines can cause cancer.

My laboratory and some in Japan, where the original discoveries were made, showed when you feed these chemicals in their pure form to rats, they get cancer of the breast, colon, pancreas and prostate. And when you put the animals on a typical high-fat Western diet, you get even more of these lesions, and you get them faster. So the principle is there. This is not something we can ignore.

I sent a young doctor I had working for me in 1977 out to three different fast food operations. One fried their meat on a hot plate; others broiled it over a charcoal fire; and the third broiled it in an oven with a gas fire on top. We bought ten hamburgers from each place, and we analyzed the thirty hamburgers for mutagenicity—we scraped the surface, extracted it, and gave it to our laboratory for testing. And about half these hamburgers, commercially bought mind you, were mutagenic. In other words, they contained appreciable amounts of these carcinogenic chemicals.

So the more brown a burger gets, the more of these fairly hazardous heterocyclic amines form. But again, if you do—if you by chance roll it over and grill it too much—that’s okay. Better that than have E. coli poisoning, you see! You have to take these matters under consideration.

I’ve developed methods to prevent the formation of these chemicals, and I’m trying to get the food industry to adopt some of my findings. If you deal with ground meat for hamburger, you can add just 10 percent soy protein and make a soy hamburger out of that, and when you cook these you don’t form these chemicals—the little soy protein contains antioxidants that prevent [the creation of amines]. I’ve also found that if you make a tea powder and sprinkle it on both sides of the hamburger, you lessen the chance of forming these chemicals, because tea contains antioxidants. That’s also why I recommend people drink tea.

There are other ways to cook meat and keep the amines away. If you precook your burger—or any kind of beef—for a few minutes in a microwave, creatinine is removed, and without creatine heterocyclic amines cannot be formed.

Or when you eat burgers, vegetables and fruits are important. Adding ketchup on the burger is important because tomato induces the enzymes that detoxify those amines in the liver, hence reducing cancer risk due to amines. So my public health recommendatoin is to eat more rice and veggies and drink tea, and have a hamburger on the side. You know, President Jefferson said that a long time ago—he said, The way I eat my meal, I put my vegetables and starches in the center, and I put the meat on the side as a condiment—rather than have it in the middle of the dish as a main part of his food!