10 Foods That Pack A Wallop

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And Now the Bad News: Potatoes

Potatoes are supposed to be one of the world's greatest foods, filled with calcium, niacin, iron, vitamin C and plenty of carbohydrates. A diet of milk and potatoes, the textbooks say, will provide all the nutrients the human body needs. But there is trouble lurking beneath the skin. According to a controversial new theory, potatoes, eaten in large quantities by a population increasingly sedentary and overweight, may be a major contributor to America's alarming rates of heart disease and diabetes.

The problem, according to Meir Stampfer, a nutrition professor at the Harvard School of Public Health, is potato starch. When you eat a potato and that starch hits the saliva in your mouth, its tightly bundled molecules immediately get turned into sugars, which make a beeline for the blood. "You ate a potato," says Stampfer, "but your body is getting pure glucose." The flood of blood sugar sets off a chain reaction. Insulin pours out of the pancreas. Triglycerides shoot up. HDL (good) cholesterol takes a dive. "It's a perfect setup for heart disease and diabetes," says Stampfer.

This is not just a potato problem. It's also a problem with white bread, bagels and most white rice. But couch potatoes don't have to give up their spuds altogether, as long as they eat them in moderation. Or they could switch to sweet potatoes and yams, which metabolize less rapidly and wreak less havoc with blood sugar.