It’s no wonder tea is one of the most popular beverages in the world.

Tea is not only delicious, soothing, and refreshing but also revered for its many potential health benefits (1).

Tannins are a group of compounds found in tea. They are known for their distinct flavor and interesting chemical properties and may also provide health benefits (2).

This article explores everything you need to know about tea tannins, including their health benefits and possible side effects.

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Tannins are a type of chemical compound that belongs to a larger group of compounds called polyphenols (2).

Their molecules are typically much larger than those found in other types of polyphenols, and they possess a unique ability to easily combine with other molecules, such as proteins and minerals (2).

Tannins are naturally found in a variety of edible and inedible plants, including tree bark, leaves, spices, nuts, seeds, fruits, and legumes. Plants produce them as a natural defense against pests. Tannins also contribute color and flavor to plant foods (3, 4).

Some of the richest and most common dietary sources of tannins include tea, coffee, wine, and chocolate.

The astringent and bitter flavors that are characteristic of these foods and beverages are usually attributable to their abundant supply of tannins (2, 5).

summary

Tannins are a type of plant compound naturally found in foods and beverages, including tea, coffee, chocolate, and wine. They’re well known for their astringent, bitter flavors and ability to easily bind with proteins and minerals.

Although tea is generally considered a rich source of tannins, multiple variables can affect the amount that ends up in your teacup.

The four main types of tea are white, black, green, and oolong, all of which are made from the leaves of a plant called Camellia sinensis (6).

Each type of tea contains tannins, but the concentration is strongly affected by the way it’s produced and how long it’s steeped when you prepare it.

Some sources say black tea has the highest tannin concentration, while green tea is often credited with having the lowest.

White and oolong teas usually fall somewhere in between, but the amount in each type can vary considerably depending on how they’re produced (7).

Generally, lower-quality teas tend to have higher tannin levels, and the longer you steep your tea, the higher the concentration of tannins in your cup.

summary

All types of tea contain tannins, but the exact amount can vary considerably depending on how the tea is produced and for how long it’s steeped.

There are many different types of tannins found in tea, and how they affect the human body is still not well understood.

However, early research suggests that certain tea tannins possess characteristics similar to those of other polyphenols, helping prevent disease by providing antioxidant and antimicrobial benefits (3).

Epigallocatechin gallate

One of the main tannins found in green tea is known as epigallocatechin gallate (EGCG).

EGCG belongs to a group of compounds known as catechins. It’s thought to be one of the reasons behind the many health benefits associated with green tea.

Animal and test-tube studies suggest that EGCG may play a role in reducing inflammation and protecting against cellular damage and certain chronic illnesses, such as heart disease and cancer (8, 9).

Ultimately, more research is needed to better understand how EGCG may be used to support human health.

Theaflavins and thearubigins

Tea also offers a plentiful supply of two groups of tannins called theaflavins and thearubigins. Black teas contain particularly high levels of these tannins, and they’re also credited with giving black teas their distinctive dark color.

At this stage, very little is known about theaflavins and thearubigins. However, early research indicates that they function as potent antioxidants and may offer protection against cellular damage caused by free radicals (10).

Most of the evidence on theaflavins and thearubigins is limited to test-tube and animal studies. More research in humans is needed.

Ellagitannin

Tea also contains high levels of a tannin called ellagitannin (11).

Early-stage research suggests ellagitannin may promote the growth and activity of beneficial gut bacteria, but more studies in this area are needed (11).

Ellagitannin is also in the spotlight for its potential effect on cancer treatment and prevention.

Like other types of dietary polyphenols, ellagitannin exhibits strong antioxidant and anti-inflammatory effects. Test-tube studies have revealed that it may also play a role in reducing the growth and spread of cancerous cells (12).

Current research is promising. However, more is needed to fully understand whether ellagitannin has cancer-fighting effects and where it might belong in a plan for cancer treatment or prevention.

summary

Certain tannins present in tea may help prevent disease and provide antioxidant and anti-inflammatory benefits. However, more research is needed to better understand their role in supporting human health.

Although tea tannins provide several health benefits, overconsumption could lead to negative side effects.

Tannins are unique in their ability to easily bind with other compounds. This feature gives tea a pleasantly bitter, dry flavor, but it can also impair certain digestive processes.

Reduced iron absorption

One of the biggest concerns with tannins is their potential ability to hinder iron absorption.

In the digestive tract, tannins can easily bind with iron present in plant-based foods, rendering it unavailable for absorption (13).

Research indicates that this effect is not likely to cause significant harm in people with healthy iron levels, but it could be problematic for those with iron deficiency (13).

If you have low iron but want to drink tea, you can limit your risk by avoiding consumption of tea with iron-rich foods.

Instead, consider having your tea between meals.

May cause nausea

The high levels of tannins in tea may lead to nausea if you drink tea on an empty stomach. This may particularly affect people with more sensitive digestive systems (6, 14).

You can avoid this effect by having your morning cup of tea with some food or adding a splash of milk. Proteins and carbohydrates from food can bind with some of the tannins, minimizing their ability to irritate your digestive tract (14).

Also, consider limiting how many cups of tea you drink in one sitting.

summary

Tannins may cause nausea and hinder your ability to absorb iron from plant-based foods.

Tannins are chemical compounds found in a variety of plant-based foods and beverages, including tea.

They’re responsible for giving tea its dry, somewhat bitter flavor and providing color in certain types of tea.

Early research suggests that tea tannins may provide health benefits due to their antioxidant and anti-inflammatory effects. However, more research is needed.

Tea tannins may cause nausea, especially if consumed on an empty stomach. They may also hinder your body’s ability to absorb iron from certain foods.

To get the most benefit from tannin-rich tea, consume it separately from foods containing iron, and make sure you drink it in moderation.