At this point, it's common knowledge that too much sugar bad for us. In fact, some doctors even think we should regulate them like we do alcohol. But given all the marketing hype behind different "natural" alternatives, it's hard to know which sweeteners really are the best. Complicating matters, studies--including one published in 2010 in the journal Cancer Research--are finding that fructose, a sugar found in high-fructose corn syrup, agave, honey, and, in much tinier amounts, even in fruit, actually feeds some cancers. That's no reason to give up on fruit or even honey, but when you're in need of a sweetener, make sure you know the difference between the good guys and the bad. And use them in moderation: "Sweeteners should, first and foremost, always be thought of as treats," says Joy Manning, nutrition editor at Prevention magazine.