The tooth enamel is a porous structure and it is susceptible to stains. Usually, colored foods and beverages are absorbed by the teeth and they leave a stain behind. Not just the color, but also the level of acidity plays a major role in the discoloration of teeth. Even if an acidic food is not brightly colored, it might still place a few stains on the teeth.

The following lists of foods are generally known to discolor or stain teeth:

Tea is a healthy drink that offers great relaxation. Black tea can cause a lot of stains to the teeth. However, a study by researchers from University of Alberta found that consumption of tea with milk might prevent teeth staining. Casein is a main protein that is found in milk and it binds to the water soluble phenolytic compound in the tea that causes stains. Thus, tea with milk might be a better option to rescue oneself from tea stains on teeth. Like tea, coffee also causes teeth discoloration. Black coffee is capable of staining the teeth, and one can avoid it by combining it with milk that reduces the stains. 

Red wine is an acidic beverage that consists of chromogens and tannins, which are responsible for staining teeth. White wine is also a notorious drink when it comes to the problem of teeth stains. At a study conducted in the New York University School of Dentistry, teeth that were exposed to tea stained severely, if it had already been exposed to white wine.

The acid and chromogens in the soda lead to serious staining of the teeth. Even if the soda is light colored, it contains enough acid to stain the teeth. Sodas form layers of sugar to the teeth that creates plaque on which the bacteria in the mouth begin to feed. As time goes by, this layer can grow further to produce a yellow effect on the teeth, and for some people it goes to an extent of getting treated by a dentist.

Tomatoes and tomato-based sauces can weaken the enamel of the tooth and allow stains to occur. Orange juice and soy sauce also have similar properties that stain the teeth brown or yellow color. Sports and energy drinks are also notorious and have the tendency to stain teeth. Therefore, it is advisable to replace these with water whenever possible, or at least keep sipping water in between consuming such drinks.

Spicy foods that contain turmeric, chili powder, and curry powders can cause a deep discoloration to the teeth and they may turn yellow. Pickles contain vinegar and are acidic in nature, and hence can cause stains. Sticky foods like candies are bad for the teeth. They provide a source of food for the bacteria to grow in the teeth and produce acids that erode the teeth. Crackers contain carbohydrates in a refined form, which turn to sugar quickly. This provides food for the acid-causing bacteria as it becomes like a paste when chewed and stick between minute gaps in the teeth. This result in a buildup of plaque, which in turn makes the teeth pale yellow.

It can thus be understood that teeth get discolored with a lot of foods and since it is not possible to avoid all of them, one must take necessary precautions and protect their teeth and ensure proper dental hygiene.