The combination of acid and sugar can actually be bad for your teeth. "The acidity of lemonade can actually erode or even completely wear away tooth enamel," says Nancy Rosen, a New York City dentist who specializes in general and restorative dentistry. "When you don't have enough enamel or it's eroded, then you move on to the next layer of tooth, which is the dentin, which is naturally very yellow."
2. Sports drinks
Although these mainly energy drinks are not as brightly coloured as coffee or tea, swallowing them can affect your teeth.
"The level of sugars in these types of drinks provides a fertile ground for the growth of all kinds of bacteria."
"Not only do these drinks stain your teeth, but they also cause decay due to their high sugar content."
3. White wine
Although red wine is worse, white wine can also stain your teeth when combined with certain foods. For example, if you have a glass or two before dinner and then eat pasta with tomato sauce, "it's like opening up the pores of your teeth to let all the color seep into them."
4. Greens juice and smoothies
Green juices and smoothies may be great for your body, but considering what they contain, they're not so beneficial for your teeth.
There is even a general rule: "Anything that stains your clothes and doesn't clean easily will stain your teeth."
Smoothies are filled with light-colored berries and vegetables that cause stains on your teeth.
The good news: That doesn't mean you should skip your favorite slimming, healthy juice. You can just use a straw to enjoy it without the harmful effects on your smile.
5. Green tea
Black tea usually makes teeth yellow or grey, but lighter greens can have the same effect on your teeth.
The best way to avoid it? "Brush your teeth 30 minutes after you've eaten or drunk anything that could hurt them."
(If you brush them within 30 minutes, something acidic can cause more damage).
6. Syrup for coughing
Colourful cough syrups, apart from the unpleasant taste they leave in your mouth, can also cause tooth decay as they contain a lot of sugar.
"Still, they also leave stains on your teeth if you take them continuously for an excessively long period of time."
7. Swimming pools
To all the swimming enthusiasts out there, the pool may be the reason you notice that brown tint to your smile.
"When you swim, you often leave your mouth open or allow the water to enter it. Then, the chemicals that clean the pool can leave a brownish tint on your teeth."
Keep in mind that this can only affect your teeth if you spend more than 6 hours a week in chemically treated pool water, which is likely to happen when you want to swim more in winter.
8. Traumatic injuries
A broken tooth or other injury to a tooth can cause you significant pain during the healing process and afterwards. If you play a sport in which you frequently sustain dental injuries, your smile can take a big hit as well.
"Whenever the teeth suffer some kind of trauma, the nerve can die and your tooth can start to turn grey, losing its colour."
9. Specific drugs
Injuries are not the only culprit for your stained smile.
"Taking medications for prolonged periods of time or other serious procedures, such as chemotherapy or radiation treatments, can change the blood flow to the teeth and change their colour from the inside."