Your hand slides into a bag of potato chips, but a twinge of guilt makes you hesitate.

Potato chips are junk food, right?Not necessarily, says a professor at the University of Rochester Medical School. "If you ask people what are junk foods, potato chips are probably one of the first things they will name," says Dr. Gilbert Forbes, who specializes in nutrition and body composition.

"But if you break down the composition of potato chips, you find that they have the same amount of protein as rice and wheat, more iron than milk, less sodium than cow's milk, and as much niacin as milk. They're low in thiamine and riboflavin, but they have a bit of Vitamin C. All in all, there's more nutritional value than in apples."

So, we can lick the grease off our fingers, dig into the chips and cast aside that old apple-a-day adage?

Well, not quite, says Forbes. "The real point is that some of the foods that get labeled as `junk' are perfectly wholesome - in moderation."