Why Does Tea Have Caffeine? How Tea Fails To Protect Itself

Tea made from camellia sinensis contains varying amounts of caffeine. Oxidation, fermentation, steaming and roasting aren’t able to change this fact. But why does tea contain caffeine?

I have wondered about the exact reasons for caffeine being a major part of tea leaves for a while. For this reason I have done some research on this and I want to share my findings here with you.

SHORT ANSWER – Why Tea Contains Caffeine

Camellia Sinensis, commonly known as the tea plant, produces caffeine as a means of protection. Caffeine inhibits the growth of fungi, such as mold, and bacteria inside and on the surface of the tea leaves. Furthermore, caffeine acts as a natural repellant for insects and other herbivores.

So tea plants, just like many other plants do, use caffeine to protect themselves from various pests and predators. But how exactly does that work and why doesn’t this protect the tea plants from humans?

Caffeine In Tea Offers Two Types Of Protection

We humans are able to consume tea and other caffeine-containing beverages on a daily basis without any harm done to us. We even use the caffeine to our advantage.

The reason for tea leaves to contain caffeine is not to make us feel awake and stay motivated but rather as a means of protection from pests and herbivores. One part of the defensive system of tea plants is a caffeine content of up to 5% in dry tea leaves. (Source)

An interesting thing to note on the caffeine contained in tea leaves is that there are two types of caffeine in the plants cells. Well, rather than types of caffeine, they differ in the way the work.

Regular Caffeine

On type of caffeine is already active inside tea tea plants cells and works as an inhibitor. This caffeine will protect the tea plant from pests such as mold and other fungi, but may also inhibit the growth of bacteria.

As caffeine can potentially be harmful to the tea plant itself, only a part of the caffeine inside the cells is active and present as regular caffeine. Otherwise, the growth of the tea plant itself might be inhibited.

Complexed Caffeine

Additionally, there is caffeine inside the tea plant that is complexed by other chemical compounds. You do not need to understand chemistry to get this concept. Caffeine that is complexed can be considered inactive.

When the tea plant is eaten by insects or other herbivores, the complexed caffeine is released and will repel the predator. The complexed caffeine will not harm the tea plant itself, but is able to protect it after it’s released.


The German language has a specific word for the caffeine contained in tea: “Teein”. The best translation for this would be “tea-ine” as it is a combination of the words tea and caffeine.

Tea Protects Itself From Insects With Caffeine

Insects are the primary predators for Camellia Sinensis, and the tea plant needs to protect itself from them. As stated above, the complexed caffeine is responsible for protecting the tea plant from insects.

The caffeine in the tea leaves prevents the insects feeding on the plant and can potentially paralyze and get rid of the predators. This is necessary for the plant to survive long enough to bloom and reproduce.

Every plant has developed a means of protecting themselves from various pests and threats. Tea and many other plants have evolved to produce caffeine for this.

Caffeine In Tea Inhibits The Growth Of Fungi

Another reason for tea plants to produce caffeine lies in the inhibiting properties of the caffeine. The caffeine in tea plants is able to inhibit the growth of fungi and mold (which is a fungus).

The uncomplexed caffeine, which is the caffeine that is active in the live tea plants cells, prevents the fungi from entering the tea plants. Fungi are not able to grow and thrive where caffeine is present.

Furthermore, caffeine is able to inhibit the growth of many plants and bacteria. This characteristic of caffeine is what protects the tea plants from parasitic plants and bacterial infections.

Tea Plants Remove Competition With Caffeine

Caffeine is a chemical compound that inhibits the growth of various plants including tea plants themselves. Because of this, many plants are unable to grow close to a tea plant.

The growth of tea plants is also inhibited by caffeine. Tea plants that have higher caffeine content are able to inhibit the growth of competing tea plants and will grow faster because of this.

Tea does not only have caffeine in the leaves, but will also release caffeine as a seedling and in its roots. This is where the caffeine is most efficient to remove competition and allow for growth.

Caffeine In Plants Is More Common In Temperate Climates

Interestingly, all plants that have evolved to produce caffeine come from temperate climates. Many plants have independently developed this chemical as defensive mechanism.

Caffeines occurrence in temperate climates comes down to the increased numbers of insects in these regions. Further, mold is more likely to grow in warm and wet conditions, which are common in temperate climates.

Tea is an evergreen plant that is very vulnerable to freezing temperatures in the first few years. Most tea plants are grown in regions that almost never see any snow or frost.

This means that tea plants grow in regions where insects are active all year round and will need to protect itself from them all the time.

In other climates, plants will not survive the winter anyways and are less dependent to defend against insects. That’s why plants in colder climates haven’t evolved to produce caffeine like other plants have.

Which Plants Other Than Tea Have Caffeine?

Tea uses, among many other plants, caffeine to protect itself. Caffeine has never been a successful repellant to humans, though, and plants containing caffeine have been made into foods for hundreds if not thousands of years.

I was very surprised when I found out that some plants, which I would never have guessed to, contain caffeine. More than 60 plants in various countries around the world have independently evolved to produce caffeine for protection. (Source)


Some citrus plants contain caffeine. The caffeine is mainly contained in the leaves and flowers of these plants and is very rarely found in the citrus fruits themselves.

  • Cassina Tea – A caffeine source native to North America. This plant is not as common nowadays, but was in American history.
  • Citrus Plants – Caffeine can be found in the leaves and flowers of various citrus plants. The fruits rarely contain caffeine, though.
  • Tea Leaves – Tea leaves have been eaten and chewed for a very long time before people started steeping the leaves to get a beverage.
  • Coffee Beans – Ground and used to make coffee. There are various sub-types of these plants which vary in caffeine content.
  • Kola Nuts – This is a common ingredient in well-known soft drinks, supplements and energizers.
  • Cacao Seeds – Made into chocolate. The consequence to this is noticeable caffeine content in chocolate. Especially dark chocolate.
  • Yerba Mate – Just like tea, this plant is steeped to yield a beverage. This beverage is gaining popularity.
  • Guarana Seeds – This is a common ingredient in various energy drinks, supplements and super-foods.

While many plants contain caffeine, tea is one of the best sources for daily consumption. Depending on how you brew your tea, tea can become much stronger than other caffeinated beverages.

Brewing stronger tea does not necessarily mean better tea. If you want to learn how to brew a strong tea that still tastes good, this article covers everything you need to know.

How Much Caffeine Does Tea Have?

The caffeine content in the leaves of tea plants varies depending on where they have been grown and the exact variety of tea. The caffeine content of tea grown in Darjeeling, India is not the same as that of tea plants grown in Yunnan, China.

Tea plants contain anywhere between 1% and 4% caffeine with most of this caffeine being inside the older tea leaves. Younger leaves contain less caffeine than older tea leaves do. Older tea leaves will contain between 3% and 4% caffeine. (Source)

Least caffeine is to be found in the stems and roots of the tea plants, because insects are much more likely to eat the leaves of the plant. Also, the leaves are more vulnerable to fungi as the surface area is larger.

There’s a lot more to learn about tea! If you are looking for a good place to start, I highly recommend the book Tea: History, Terroirs, Varieties. You can check its current price on Amazon here.