Digestive Side Effects of Black Tea

Black tea contains beneficial plant-based flavonoids.
Image Credit: HappyNati/iStock/GettyImages

Black tea is better known for its benefits than for any type of side effects. But, black tea can affect your stomach. While you might even drink herbal tea for upset stomach and diarrhea, black tea could make your symptoms worse.


It contains two natural substances — caffeine and tannins — that have the potential to cause digestive problems, such as an upset stomach or nausea. The key is to enjoy black tea but don't go overboard. Only large amounts of caffeine and tannins are likely to produce unwanted side effects.

Video of the Day

Video of the Day

Read more: 6 Teas to Stock Up On and Their Health Benefits

Understand Benefits of Black Tea

Green and black tea are both made from the leaves of the Camellia sinensis plant, so they start out with the same plant-based substances called flavonoids. The leaves are simply steamed and dried to produce green tea. To make black tea, they're allowed to ferment.

During the fermentation process, the flavonoids change. As a result, black tea ends up with different flavonoids than those in green tea. The black tea flavonoids, called thearubigins and theaflavins, may also offer health benefits, such as lowering your risk of having a heart attack, according to the Linus Pauling Institute.

Consider Caffeine Consequences

If you notice stomach pain after drinking tea, caffeine might be the culprit. Caffeine can cause several problems in the digestive tract. It boosts the amount of acid in your stomach, which can give you an upset stomach or cause heartburn.


It also has a diuretic effect, so you probably won't have an issue with black tea and bloating. As a result, more fluids are eliminated through your urine and may become dehydrated.

When you consume caffeine, it stimulates the muscles that push wastes through your digestive tract. While this can help if you're constipated, it may result in diarrhea.


Caffeine can also aggravate gastrointestinal conditions such as irritable bowel syndrome, reports the University of North Carolina Wilmington.

Tannins: Side Effects

Tea contains natural substances called tannins, which contribute color and a slightly bitter flavor. If you drink a moderate amount of black tea, tannins should not cause problems. In large quantities tannin's side effects can include upset stomach, or cause nausea and vomiting.



Tannins may interfere with the absorption of nonheme iron, which is the type of iron found in plant-based foods. However, according to a 2017 article published by Current Developments in Nutrition, more long-term studies are needed in this area.

Read more: What Are the Health Benefits of English Breakfast Tea?

Enjoy in Moderation

Drinking up to 400 milligrams of caffeine daily is safe for most healthy people, reports the U.S. National Library of Medicine. With 42 milligrams to 79 milligrams of caffeine in an 8-ounce cup of black tea, as reported by Linus Pauling Institute, that works out to a maximum of 4 cups to 10 cups daily, depending on the actual caffeine content of the tea.


You can reduce some of the caffeine by brewing the leaves for a shorter amount of time. A cup of tea brewed for one minute has half the caffeine as tea that was steeped for three minutes.




Report an Issue

screenshot of the current page

Screenshot loading...