Weird, but true. A recent study found that the more physically active participants were, the more dental erosion they had. Panting and sweating can lead to dry mouth, and athletes, the study found, produce less mouth-rinsing saliva during workouts. Combine that with the sugar and carbs in sports drinks and bars and you’ve got a recipe for cavities. Keep drinking water when you exercise—good advice for anyone—and pop a sugar-free mint or gum after your workout to get the saliva flowing again.