Smoking is one of the most common causes of stains and yellowing teeth. However, there are several types of food and beverages that are particularly effective at staining your teeth, too:
Hot Coffee and Tea — Coffee and tea both contain elements that will stain your teeth. However, the heat of these beverages make the situation even worse: As the drink warms your teeth it causes them to expand, making them more porous and allowing the stains to penetrate deeper.
Acidic Foods — Acidic foods can cause the pores in the enamel of your teeth to open, allowing stains to move deeper into the enamel.