Fruit smoothies can cause dental erosion – which can lead to tooth sensitivity and wear away the enamel. In fact, when researchers exposed teeth to an hour’s worth of sipping a smoothie, the enamel weakened by nearly 40%! That’s because smoothies can be highly acidic. So switch to a smoothie with milk or yogurt in it, too. Because the calcium will help minimize the enamel-softening effects of the acid.