Tea can cause indigestion, especially when consumed on an empty stomach, in large amounts, or very hot. The main culprits are caffeine, tannins, and the temperature of the drink itself. Whether tea bothers your stomach depends on the type of tea, how you prepare it, and your individual sensitivity.
How Caffeine in Tea Triggers Acid Production
Caffeine is one of the strongest drivers of stomach acid secretion. It activates bitter taste receptors on the acid-producing cells in your stomach lining, triggering a signaling chain that pumps more protons (the building blocks of stomach acid) into your stomach. Research has shown that this process works through a specific cellular pathway involving a molecule called cAMP, and caffeine increases cAMP levels by about 12% in these cells within 10 minutes.
A standard cup of black tea contains roughly 40 to 70 mg of caffeine, compared to 80 to 100 mg in coffee. That’s enough to meaningfully boost acid output. In fact, tea without milk or sugar produced an acid response in one study that was higher than what a maximum dose of histamine (a medical-grade acid stimulant) could provoke. If you already run high on stomach acid or have a sensitive stomach, that extra surge can tip you into discomfort, bloating, or a burning feeling in your upper abdomen.
Tannins and the Empty Stomach Problem
Tannins are the compounds that give tea its pleasantly bitter, slightly dry taste. They also bind easily to proteins and other molecules, and when there’s no food in your stomach to absorb them, they can irritate your stomach lining directly. This is why drinking strong black tea first thing in the morning is a common trigger for nausea, gas, and that sour, unsettled feeling in your gut.
The fix is straightforward: eating something before or alongside your tea gives the tannins something to bind to other than your stomach lining. Proteins and carbohydrates from food are especially effective at neutralizing tannins before they cause irritation. If you notice that tea only bothers you in the morning but not after lunch, the empty stomach is almost certainly the reason.
Tea, Reflux, and the Esophageal Valve
Beyond stomach discomfort, tea can also cause or worsen acid reflux. A crossover study of 12 healthy volunteers measured what happened to the valve between the esophagus and stomach (the lower esophageal sphincter) after drinking tea, regular coffee, decaffeinated coffee, or water. Both tea and regular coffee, each containing 160 mg of caffeine, significantly lowered the pressure of that valve compared to water. Decaffeinated coffee did not.
Lower pressure in that valve means stomach acid can splash back up into your esophagus more easily. The study found that tea actually produced the greatest number of reflux episodes of any drink tested, and the difference from water was statistically significant. If you experience heartburn or a sour taste in the back of your throat after tea, this relaxed valve is the mechanism at work.
Peppermint tea deserves a special mention here. While it’s caffeine-free, peppermint itself relaxes the esophageal sphincter muscle. For people prone to reflux, peppermint tea can make symptoms worse even though it contains no caffeine at all.
How Tea Type Affects Acidity
Not all teas are equally acidic. Black tea has a pH between 4.9 and 5.5, making it mildly acidic. Green tea is much more neutral, with a pH of 7 to 10. Herbal teas like chamomile, mint, and fennel fall in the 6 to 7 range, which is close to neutral.
If black tea consistently bothers your stomach, switching to green tea or a gentle herbal like chamomile may solve the problem entirely. The lower acidity combined with lower caffeine content (green tea has about 20 to 45 mg per cup) means less acid stimulation and less direct irritation. Ginger tea is another option worth trying. Ginger speeds up gastric emptying, reducing the half-emptying time of the stomach from about 16 minutes to 12 minutes in people with functional dyspepsia. Faster emptying means food and acid spend less time sitting in your stomach, which can reduce that heavy, bloated feeling.
Temperature Matters More Than You Think
Drinking tea very hot adds another layer of irritation. The International Agency for Research on Cancer classifies beverages above 65°C (149°F) as probably carcinogenic, specifically because of thermal damage to the esophagus. You don’t need to worry about cancer from your daily cup, but that same heat irritates the lining of your esophagus and stomach in the short term, compounding any discomfort from caffeine or tannins.
Letting your tea cool for a few minutes after pouring, or adding a splash of cold milk, brings the temperature below that irritation threshold. This is a simple change that can make a noticeable difference if you tend to drink your tea as soon as it’s brewed.
Ways to Reduce Tea-Related Indigestion
- Don’t drink tea on an empty stomach. Even a small snack gives tannins something to bind to and buffers the acid response.
- Add milk or sugar. Both reduce tea’s ability to stimulate stomach acid. Milk proteins bind tannins, and the overall acid response drops measurably.
- Steep for less time. A shorter brew extracts fewer tannins and less caffeine. Three minutes instead of five makes a difference.
- Switch tea types. Green tea is far less acidic than black tea. Chamomile and fennel are gentler still.
- Let it cool. Waiting until your tea is below 60°C (140°F) reduces thermal irritation to your esophagus and stomach.
- Avoid peppermint tea if you have reflux. Its muscle-relaxing properties work against the valve that keeps acid out of your esophagus.
Population-level surveys in the US and Europe have not found a strong link between normal tea consumption and chronic dyspepsia, which suggests that for most people, tea is not inherently harmful to digestion. The problems tend to arise from specific circumstances: too much, too strong, too hot, or on an empty stomach. Adjusting how you drink tea is usually enough to eliminate the discomfort without giving it up.