The subtle role of caffeine in tea leaves

Caffeine is a naturally occurring stimulant found in coffee plants, tea leaves, and cacao beans, among others. Chemically, caffeine is classified as an alkaloid, belonging to the methylxanthines. It is part of the natural defence mechanism of the tea plant.

It has a number of effects on the body, with the stimulating effect being the most well known: it stimulates the nervous system, the heart, and the lungs.

The origins of caffeine

The discovery of caffeine takes us back to the early 19th century, when a German physician studied coffee and all its associated components. Eight years later, he discovered a similar substance in tea, which he initially named "theine". Research eventually demonstrated that both substances were identical.

Caffeine in tea vs. coffee

Both tea and coffee therefore contain caffeine, but how much exactly? Tea contains on average 2.5 to 3.5 per cent caffeine per mg, while coffee contains 1 to 1.7 per cent per mg. But we use less loose tea per cup, on average around 3 to 4 grams of tea leaves. As a result, a cup of tea contains on average 26 mg of caffeine, roughly 3.5 times less than the average 94 mg of caffeine in a cup of coffee (made with 8.3 grams of ground coffee).

What makes caffeine in tea different?

When comparing caffeine in tea and coffee, there are some important differences. Tea contains L-theanine, an essential amino acid that influences neurotransmitters and thereby improves mental focus, cognitive performance, and general mood. Caffeine in tea works in combination with the natural relaxants and antioxidants, such as EGCG and L-theanine. This produces a gradual energy boost and a feeling of calm.

Unlike coffee, where caffeine molecules are freely available, the bound caffeine in tea must first be separated from other molecules. This results in a much slower and milder effect.

A further distinction arises from the different production methods of tea: the robust processing of black tea accelerates the uptake of caffeine and therefore provides a faster energy boost. This contrasts with the gentler processing of green tea, which produces a delayed, more sustained effect.

The brewing method, specifically the water temperature and steeping time, adds an additional layer of complexity. All of these factors contribute to a milder energy experience compared to the immediate kick of coffee.

Caffeine content in different tea types

Black tea, fully processed during production, generally provides the most pronounced caffeine effect. The caffeine content in oolong, green, and white tea is somewhat lower, but much depends on the harvesting method, production methods, water temperature used, steeping time, and other factors.

Herbal infusions, made from herbs and therefore not derived from the Camellia sinensis plant, are entirely caffeine-free. Looking for an immediate energy boost? Matcha is the recommendation. Matcha is made from ground green tea leaves and provides an extra dose of caffeine because you are drinking the leaves themselves, as opposed to other teas where you use the leaves only to prepare the infusion.

The amount of caffeine in tea does not therefore necessarily depend on the degree to which the leaves have been processed. It is more a combination of several complex factors. Below is an overview of the average caffeine content per cup of tea. You will find that you can easily drink several cups before reaching the maximum daily caffeine intake of 400 mg.

• Black tea: average 30–40 mg/cup, up to 65 mg/cup
• Green tea: average 10–40 mg/cup, up to 50 mg/cup
• Oolong tea: average 18–20 mg/cup, up to 40 mg/cup
• White tea: highly variable, 5–65 mg/cup
• Coffee: average 85–100 mg/cup
• Matcha: average 70–120 mg/cup

Other influences on caffeine content in tea

It is now clear that the type of tea (green, black, white, oolong, etc.) is not the determining factor for caffeine content. Several other factors influence the caffeine content in tea leaves:

• Environment: Soil quality, sunlight, humidity, altitude, and shade all influence the composition of the tea leaf, and therefore the caffeine content.
• Fertilisation: Artificial fertilisers promote the growth of the tea plant and thereby lead to higher caffeine levels compared with more naturally grown tea.
• Parts of the plant used: Although buds or blossoms are assumed to contain less caffeine, their caffeine content is in fact higher than that of mature leaves.
• Harvest season: Tea harvested in spring is said to contain more caffeine than leaves picked during summer or autumn.
• Steeping time: Caffeine dissolves readily in water, so a longer steeping time increases the caffeine content. Other techniques, such as cold brew, extract less caffeine and tend to produce a sweeter drink.

Conclusion

Caffeine is a natural substance found in plants such as coffee beans and tea leaves. Tea contains caffeine, but the amount per cup is generally considerably lower compared with an average cup of coffee. The interaction with other components in the tea plant also produces milder effects compared with the effects of caffeine in coffee.

Each type of tea has a different caffeine content, and this is not necessarily the result of different production methods. Factors such as soil quality, the parts of the plant used, and steeping time also play an important role.