Running does wonders for your body, from decreasing body fat, relieving stress, lowering cholesterol and strengthening your heart. It also lends you a fabulous dose of feel-good endorphins. But it might not be so great for your endorphin-induced smile. As it turns out,Halloween candy isn’t the only culprit for cavities.

The new study from the Department of Conservative Dentistry at the University Hospital in Heidelberg, Germanyfound that runners’ and triathletes’ high consumption of carbohydrates combined with low saliva output makes for a rotten recipe: tooth erosion. While the endorphin junkies enjoyed the benefits of low body mass indexes, those who trained more also happened to have more cavities. The researchers also measured their saliva before and during the athletes’ workouts and discovered that the longer they sweat, the more acidic their saliva become. Healthy saliva is essential for breaking down food for digestion.

Another study published in the journal General Dentistry found that sports drinks and energy drinks cause damage to tooth enamel. Interestingly, energy drinks caused twice as much damage to teeth as sports drinks.

So what’s a runner to do? Unless you’re exercising for more than an hour or in hot and humid conditions, water should be your primary beverage of choice. But if you must guzzle a sports drink or energy drink, be sure to rinse your mouth after your workout. Chewing sugar-free gum can also decrease the level of acidity in your mouth. Even better, brush your teeth — but wait an hour after your last sports drink or you could just make it worse. Reap the benefits of being a runner, cyclist or swimmer … but take care to keep your smile pearly white, too.