How much caffeine is there in a cup of tea?
By Isabelle Wilkinson
We are often asked about how much caffeine there is in tea, but the answer is not as straight forward as a specific measurement. Four factors interplay to determine the amount of caffeine absorbed by the body when drinking tea, and the additional presence of natural amino acids, such as L-theanine, means that the caffeine released in a cup of tea will affect the body differently to the equivalent amount in a cup of coffee. Here we share our knowledge on what caffeine is, the factors that determine how much is consumed and how we can use tea as a more sustainable way to power through the day.
What is caffeine?
Caffeine is a stimulant which activates the heart and nervous system, providing energy, heightened alertness and increased mental and physical endurance levels. Naturally occurring, caffeine is extracted from the leaves, seeds and fruits of many plants, but most commonly coffee beans, cocoa and tea. The reason caffeine is found in these plants is thanks to its ability to act as a natural pesticide, protecting them from insects that attempt to eat their leaves.
What does caffeine do to the body?
Once ingested, caffeine is absorbed into the blood and body tissues in roughly half an hour. This then disrupts the function of one of the body’s key sleep-inducing molecules, adenosine, which, when uninhibited, causes us to feel sluggish by slowing the release of important brain signalling molecules. Caffeine blocks adenosine from functioning, and as such, acts as a stimulant.
How much caffeine does tea contain?
The question of how much caffeine a cup of tea contains is not straightforward. Each cup of tea’s content is dependent on several factors:
The properties of the leaf
The amount of tea used
The temperature of the water used to brew
The length of the infusion
The location in which the plant has been grown, the soil quality, the weather and many other factors will play a role in its base caffeine content. For example, the young bud and first leaf of a plant generally have slightly more caffeine than leaves picked from the lower part of the tea bush.
Amount of tea
The more loose leaf tea that is used per cup, the more caffeine there will be in the resulting liquor. Black teas, for example, tend to require the most dry leaf per cup - roughly 3g for a 200ml pot - as opposed to 2.5g for some oolongs or even 2g for a white tea.
The brewing temperature will also determine the amount of caffeine that is released into the cup. A lower water temperature, 70 degrees for example, will result in less caffeine than in a cup of tea that has been brewed in water just off the boil. This is perhaps where the myth that black tea contains more caffeine than green or white teas comes from, when in fact it is not the tea type itself, but the brewing parameters that influence the amount of caffeine released.
Much like water temperature, the length of time that the leaf is brewed for is also an important factor. The longer a tea is steeped for, the more caffeine is released into the liquor, and conversely a tea that is only left to brew for 2 minutes will result in a less caffeinated cup. There is, therefore, some truth in us crying out for a really strong cuppa when we need that extra push to get us going in the morning.
How does caffeine in tea differ to that in coffee?
Caffeinated tea affects the body differently to coffee. The former is like having a bowl of porridge for breakfast, the latter a bar of chocolate. Both will give you energy, but while coffee will release it quickly, often swiftly followed by a crash, tea's 'energy' will be released slowly, over a much longer period of time. This is largely because, as well as caffeine, tea also contains L-theanine, a natural amino acid that not only has calming properties of its own, but also slows down the release of caffeine into the bloodstream. The presence of both substances therefore results in a more balanced energy experience. Another contributing factor is the amount of raw of ingredient that goes into making a cup of tea compared to that of coffee. When making comparisons about the caffeine content in coffee and tea, people rarely know that tea actually contains more caffeine than coffee on a dry weight basis. However, when it comes to preparing a cup of tea, far less dry leaf is needed than the amount of coffee beans required to make a coffee. When we’re brewing an Earl Grey for example, we might use 3.5g of loose leaf for a 200ml mug, while a coffee of the same size would require more like 16g of coffee.
You can now perhaps understand the challenge in answering the seemingly straightforward question of how much caffeine is in tea, but hopefully this sheds some light on the topic. To conclude, it depends on the variety of leaf, the brewing time and temperature and finally the amount of leaf used in each cup. For more information, we recommend reading here.