Since he ditched Marlboro Lights five years ago, Daniel's fix is fruit-flavored nicotine gum that comes in neat, pop-out strips. He gets through 12 to 15 pieces a day and says he has "packets of the stuff" stashed all over. But he doesn't see himself as a nicotine addict.

Like many people, Daniel believes nicotine gum is far less harmful for him than smoking. Doctors worldwide agree. By giving up cigarettes, they say, Daniel has removed at least 90 percent of the health risks of his habit.

Even so, the possibility that people can be addicted to nicotine, but not die from it, is at the heart of a growing debate in the scientific community. Scientists don't doubt nicotine is addictive, but some wonder if a daily dose could be as benign as the caffeine many of us get from a morning coffee.