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?

Is there caffeine in tea? Many believe there to not be much caffeine in tea, or don’t consider it as potent as coffee, and in some instances this is the case. However, the question of “does tea contain caffeine?” is not straightforward. Each cup of tea’s caffeine 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

Leaf properties

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.

Water temperature

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.

Infusion time

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.