Sugar gets most of the headlines, but many foods can cause tooth decay. The bacteria in our mouths enjoy carbohydrates from "healthy" foods as well. How often we eat also plays a role. Constant snacking keeps our teeth in contact with food more often and allows plaque to thrive.
It is important to brush after every meal to keep the bacteria colonies at bay. The faster food particles are removed, the better your chances of avoiding decay. Oh, and visiting the dentist regularly can't hurt either.
Go ahead, live in the spirit of the day. Just don't forget sound oral hygiene for the other 364 as well. Happy Halloween.