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Most lists of foods that stain teeth repeat the same names without saying how they know. This guide looks at what lab studies have actually measured, then at what that means for eating and drinking in Bangkok.
Which foods and drinks stain teeth the most?
In lab studies, black tea, red wine and soy sauce stain tooth enamel the most. Coffee comes next. White wine, curry and ketchup stain far less than their reputation suggests. These are tests on enamel samples, not on people, so treat them as a guide.
| Food or drink | Why it stains | What studies show | What to do |
|---|---|---|---|
| 1. Black tea | Tannins and pigment | Highest staining of 11 drinks, and the hardest stain to brush off (2022 lab study) | Add milk. Rinse with water |
| 2. Red wine | Pigment, tannins and acid | Among the most staining in several lab studies | Drink water alongside |
| 3. Soy sauce | Dark pigment | The most staining of 8 sauces: visible change within 3 hours of soaking (2025 lab study) | Use less. Rinse after the meal |
| 4. Coffee | Pigment and tannins | Significant staining, less than black tea in the 2022 study | Add milk. Don’t sip it all day |
| 5. Cola and sports drinks | Acid, more than colour | Staining from diet cola was linked to its acidity | Use a straw. Don’t brush straight after |
| 6. Fish sauce | Pigment | Visible change within 3 hours of soaking, well below soy sauce | Rinse after the meal |
| 7. Berries and dark juices | Strong pigment, some acid | No published measurement on enamel found | Rinse with water |
| 8. Beetroot, balsamic vinegar, coloured sweets | Strong pigment or acid | No published measurement on enamel found | Rinse with water |
| 9. Tomato sauce and ketchup | Acid and red pigment | Ketchup caused minimal staining in the 2025 study | Little to worry about |
| 10. Curry and turmeric | Bright yellow pigment | Minimal staining on enamel in the 2025 study, despite the colour | Little to worry about for natural teeth |
Tobacco isn’t a food, but it belongs on any list: the American Dental Association names it among the main causes of surface stains.
Why some foods stain: pigment, tannins and acid
- Pigment. Strongly coloured compounds cling to the enamel. Example: soy sauce.
- Tannins. Plant compounds that help pigment stick. Example: black tea.
- Acid. It softens and roughens the enamel surface, so stains set more easily. Example: cola.
Colour alone doesn’t predict a stain. The authors of the 2025 study concluded that the chemistry of the pigment matters more than how vivid it looks.
These are surface stains. The American Dental Association describes them as coloured compounds that build up on the enamel. They are different from the natural colour of the tooth.
Drinks that stain teeth
Tea or coffee: which stains more?
In the 2022 study, black tea stained more than coffee and its stain resisted brushing best. An older study from 1981 found the opposite. Both stain, and how often you drink them matters more than which one you choose.
Does milk in tea or coffee help?
Yes, partly. A 2014 lab study found that adding milk significantly reduces tea’s ability to stain teeth, thanks to a milk protein called casein. Tea and coffee with milk still stain more than water.
Red wine and white wine
Red wine is among the most staining drinks in several lab studies. White wine stained about as much as water in the 2022 study. It’s still acidic.
Cola, diet cola, sports and energy drinks
Here the problem is acid rather than colour. Sugar-free versions are just as acidic.
Foods that stain teeth
Soy sauce and other dark sauces
Soy sauces topped the 2025 study, ahead of fish sauce, curry, ketchup and sriracha. Keep in mind that the samples were soaked for hours. A meal is a much shorter contact.
Curry and turmeric: less than you’d think
Curry barely stained enamel in the 2025 study. Only one product was tested, so this isn’t the final word. Turmeric does stain some dental materials, such as clear aligners and the elastic bands on braces.
Berries, beetroot, tomato sauce and coloured sweets
- Berries and beetroot: strongly pigmented and named everywhere, but we found no study measuring them on enamel.
- Tomato sauce: acidic. Ketchup caused minimal staining in the 2025 study.
- Coloured sweets and ice lollies: a rule of thumb, not a measured fact: what colours your tongue can colour your teeth.
Eating and drinking in Bangkok: what to watch
None of these dishes has been studied as such. This table reasons from their ingredients.
| In Bangkok | What’s in it | What we know | Tip |
|---|---|---|---|
| Thai iced tea (cha yen) | Black tea, often an orange colouring, condensed milk | Not studied. Black tea stains. Milk reduces it | Rinse with water afterwards |
| Iced black coffee (oliang, kopi) | Coffee | Coffee stains in lab studies | Finish it rather than sipping for hours |
| Soy-based dishes (pad see ew, dipping sauces) | Dark soy sauce | The most staining sauce tested | Drink water with the meal |
| Fish sauce | Fermented fish | Visible in the lab, less than soy | Nothing special |
| Curries (yellow, massaman, khao soi) | Turmeric and spices | Minimal staining on enamel in one study | Enjoy |
| Tamarind (pad thai, juices) | Acidic fruit | Acidic enough to be used as an erosive drink in a Thai lab study | Wait before you brush |
| Dark juices and smoothies (berries, beetroot, pomegranate) | Pigment and acid | Not studied on enamel | Use a straw |
Foods that don’t stain your teeth
“Non-staining” here means pale and low in acid. It isn’t a tested category.
- Drinks: water, milk, coconut water.
- Dairy: plain yoghurt, cheese.
- Staples: rice, rice noodles, eggs, tofu.
- Protein: chicken, white fish.
- Fruit and vegetables: banana, pear, apple, cauliflower, cucumber.
| Instead of | Try |
|---|---|
| Black tea | Tea with milk, or a pale herbal tea |
| Cola | Sparkling water |
| Dark soy sauce | Light soy sauce, in a smaller amount |
| Red wine | White wine, with water alongside |
As for foods that “whiten” teeth: in a lab comparison, a home-made mix of strawberry and baking soda was the least effective whitening method tested.
How to prevent stains: what’s proven and what isn’t
| Habit | What the evidence says | Verdict |
|---|---|---|
| Rinse with water | Advised by dental associations. No study measures its effect on colour | Sensible, free |
| Use a straw | Reduces contact with the teeth when placed towards the back of the mouth. Measured for acid erosion, not stains | Plausible |
| Add milk to tea or coffee | Reduced staining in lab studies | Helps |
| Wait before brushing after acidic food | The American Dental Association says an hour. The UK’s Oral Health Foundation says at least 30 minutes | Rinse with water while you wait |
| Brush twice a day with a whitening toothpaste | Brushing and whitening toothpaste reduce many surface stains (ADA) | Proven for surface stains |
| Don’t sip for hours | The longer the contact, the deeper the stain, in a lab study | Sensible |
| Eat crunchy vegetables | Common advice. No study found | Unproven |
Already stained? What removes food and drink stains
- Surface stains: brushing and a whitening toothpaste. See our guide to the best whitening toothpaste in Thailand.
- Stains stuck to tartar: a professional cleaning. More in teeth cleaning in Bangkok.
- A lighter shade overall: whitening. See how to whiten teeth fast.
Before and after an LED whitening session at The Smile Bar.
Just had your teeth whitened?
The rules are different for the first 72 hours. The full list is in what to eat after teeth whitening. With the Nano Protection add-on (750 THB), we lift the 72-hour rule.
Book a whitening session at The Smile Bar
The Smile Bar studio in Siam Square, Bangkok.
- Single Whitening: 1 × 20 minutes, 2,399 THB
- Double Whitening: 2 × 20 minutes, 4,399 THB
- Triple Whitening: 3 × 20 minutes, 5,799 THB
- Cleaning and Scaling: 950 THB, performed by our dentist, only together with a whitening session
Results range from 2 to 9 shades lighter, 5 on average. Book online or walk in when a chair is free. We’re on the ground floor at 392/27-28 Siam Square Soi 5, next to BTS Siam, open every day from 10 am to 8 pm. Prices are on our teeth whitening prices page.
Frequently asked questions
What stains teeth the most?
In lab studies, black tea, red wine and soy sauce. Tobacco is also a major cause of stains.
Does Thai tea stain teeth?
No study has tested Thai iced tea. It’s made with black tea, which stains, and condensed milk, which reduces staining in lab tests. Rinse with water afterwards.
Can Thai food stain my teeth?
Dishes with dark soy sauce are the most likely to. Curries stained very little in the one study that tested curry on enamel.
Does green tea stain teeth?
It’s paler than black tea, and we found no measurement for it. It still contains tannins, so rinsing with water is a good habit.
Does Diet Coke stain teeth?
It can. In a lab study its staining was linked to its acidity, and being sugar-free doesn’t change that.
Does chocolate stain teeth?
We found no study measuring it on enamel. Dental sites often list dark chocolate, without a source.
Can whitening toothpaste remove coffee and tea stains?
It reduces surface stains. It doesn’t change the natural shade of the tooth, and tea stains go deeper than most.
