Still, gum experts say that many questions remain with using gum to deliver drugs or nutrients. Gum can contain as many as 70 ingredients, they note, and variations allow for thousands of possible gum base formulations. Interactions among ingredients can change their effectiveness -- and scientists haven't yet figured out how much of a drug or nutrient a stick of gum can hold or whether any given substance will be released or absorbed by the body when chewed.

Many studies show that chewing gum after meals fights cavities by stimulating the production of saliva, which neutralizes the acid produced by bacteria in our teeth. A 2004 study led by [Christine Wu] and funded by Wrigley found that chewing the company's Big Red gum cut bad- breath bacteria in the mouth by more than half immediately after it was chewed. (The same would probably be true for other cinnamon- flavored gums, Wu says.)

Even if chewing some gum is good, too much chewing can be harmful. The repetitive stress can worsen pain in people with jaw, or temporomandibular, joint problems, says Dr. Eric Shapira, a spokesman for the Academy of General Dentistry. And that's not the only potential problem. Tooth-whitening gum in large doses can irritate the gums, Shapira says. Vitamin C gums can create an acidic environment that wears away tooth enamel. And a kid who chews too much vitamin gum risks iron poisoning.