How does the food I eat cause decay?
The food that you chew and eat leaves a residue in your mouth, and nothing could make the bacteria that live in your mouth happier. Bacteria love the sugars and starch found in many foods. If you don't clean your teeth thoroughly after eating, bacteria will use the sugars and starch to produce acids that can eat through the enamel on your teeth. After a while, tooth decay begins. The more often you eat and the longer food residue stays in your mouth, the greater the potential for damage.
You may be surprised to learn that some foods that are otherwise very good for you are also high in sugars and starch. Just some examples are fruit, milk, bread, cereal and even vegetables. You don't have to stay away from these foods. In fact, they're part of a balanced diet. But keep in mind that foods eaten as part of a meal – as opposed to a snack – cause less harm because you produce more saliva during a meal. That helps wash food residue from the mouth and lessens the impact of acids.
Finally, limit your snacks. Each time you eat food with sugar or starch, acids attack your teeth for 20 minutes or more.