A complete guide on caffeine in tea
Caffeine is one of the most talked-about topics in tea. Some people want as much caffeine as possible for a morning wake up, while others want as little as possible for an evening wind down.
In this article, you will learn:
how much caffeine is actually in different teas
why black tea does not always have more caffeine than green tea
what factors you can control, and what you cannot
how to brew for more caffeine or less caffeine
the truth about decaf tea
What is caffeine?
Caffeine is a natural stimulant. In Camellia sinensis, caffeine serves a few purposes:
natural pesticide that paralyses or kills small insects that try to eat the leaves
inhibits growth of competing plants nearby via a process called allelopathy (hence acting like some sort of herbicide),
concentrated in young leaves and buds to protect them as they are the most vulnerable
Caffeine blocks adenosine receptors in your brain, and adenosine is the chemical that makes you feel tired. When caffeine blocks the receptors, your brain no longer takes in adenosine. In the absence of adenosine, you magically feel more alert and less tired.
Tea contains caffeine but it also contains L-theanine, an amino acid that promotes relaxation, calmness, and a state of focus. This is why tea drinkers usually describe being calm and alert, that is different from coffee’s sharper, sometimes jittery energy spike.
How much caffeine is actually in tea?
The exact caffeine content of any tea depends on many variables. Two cups of black tea can have very different amounts of caffeine.
Here are some numbers based on averages (and not exact amounts) for a cup of tea brewed with one tea spoon of tea leaves or one tea bag. For purposes of standardisation, the tea is steeped for three to five minutes.
White tea typically contains 15 to 30mg of caffeine. However, some white teas made from young buds can contain 50 to 60mg of caffeine as buds are naturally higher in caffeine.
Green tea typically contains 25 to 45mg of caffeine. Matcha can have 50 to 80mg of caffeine (sometimes more!) as you are consuming the whole ground leaf.
Oolong tea typically contains 30 to 50mg of caffeine. Heavier, more oxidised oolongs may have more, but the difference is small.
Black tea typically contains 40 to 60mg of caffeine. Some Assam black teas can have even 70 to 90mg.
Puerh tea typically contains 30 to 50mg of caffeine, and this amount dips over time as the puerh ages. The caffeine degrades very slowly over decades.
Herbal tisanes have no caffeine.
For comparison, a cup of coffee typically contains 80 to 100mg caffeine, sometimes more. Tea generally has about half to one-third the caffeine of coffee.
Debunking the myth of “black tea having more caffeine than green tea”
This is the most common misconception about tea, and it is not accurate.
To be fair, the idea seems logical. Black tea tastes stronger and darker, so it must have more caffeine. But taste and caffeine are not correlated. For instance, decaf coffee still tastes like coffee. Dark roast coffee actually has slightly less caffeine than light roast as the caffeine is burnt off during roasting.
The same principle applies to tea. Therefore, a black tea does not automatically have more caffeine.
Oxidation processes that turns green tea into black tea does not change caffeine levels. A green tea made from young buds and Assamica bushes can easily have more caffeine than a black tea made from older leaves and Sinensis bushes. A cup of gyokuro (green tea) can have 50 to 70mg caffeine. A cup of Darjeeling black tea might have only 30 to 40mg. The green tea has almost twice the caffeine of the black tea.
So do not assume black tea is your best choice in the morning, it depends entirely on the specific tea.
What actually determines caffeine levels
Six main factors determine how much caffeine ends up in your cup. Some are decided by nature, while some are decided by the tea maker. Some are in fact decided by you!
Factor 1: The tea variety
Camellia sinensis var. assamica is native to the Assam region of India. It has larger leaves and grows in tropical climates, and naturally contains significantly more caffeine.
Camellia sinensis var. sinensis is native to China. It has smaller leaves and can tolerate colder climates, and naturally contains less caffeine. It naturally contains less caffeine.
Factor 2: Leaf age and position on the bush
Caffeine is usually concentrated in the youngest parts of the tea plant, i.e. the buds and the first two leaves. These are the parts that need the most protection from insects.
This is why white teas made exclusively from buds, like Silver Needle), can have surprisingly high caffeine for a “light” tea.
Factor 3: Growing conditions
Tea plants grown under shade contain higher caffeine.
When a tea plant is shaded before harvest (like in the case of gyokuro and matcha), the plant produces more chlorophyll and more L-theanine. It also produces more caffeine as a stress response.
Factor 4: Harvest season
Spring teas usually have higher caffeine than later harvests.
During winter dormancy, the tea plant goes through hibernation and stores everything it needs, including caffeine precursors. Come spring, these stored substances flood into the new shoots. Spring leaves are packed with everything, from L-theanine, to sugars, to… you got it, caffeine.
Teas from subsequent harvests have much less caffeine as the stored reserves has already been used up.
Factor 5: Processing method
Most processing methods do not affect caffeine levels, save for one method: roasting. When tea is roasted at high temperatures, some caffeine is lost.
Factor 6: Brewing method
This is the factor that you have the most power over.
Here’s how brewing affects caffeine extraction:
water temperature
hotter water extracts caffeine faster
boiling water will pull out more caffeine in three minutes than 80°C water will in five minutes
if you want less caffeine, use cooler water, and if you want more, just crank up the heat!
steeping time
caffeine extracts quickly in the first few minutes
a thirty second steep will have less caffeine
a five minute steep will have much more
beyond five minutes, the caffeine content significantly drops as most caffeine has been extracted
leaf to water ratio
more leaves = more caffeine
multiple infusions
the first steep will always have the most caffeine
subsequent steeps will have less caffeine
Caffeine levels by tea types
Here’s a quick summary with examples, compiled based on all the above factors we have discussed:
Very low caffeine
hojicha
kukicha
bancha
Low to medium caffeine
most white teas, especially if they are aged (except Silver Needle)
most Chinese green teas
most Darjeeling black teas
most light oolongs
Medium to high caffeine
most Chinese black teas
most raw puerhs
Japanese sencha
High caffeine
Assam black tea
Silver Needle
Gyokuro and Kabusecha
young raw puerh
Very high caffeine
matcha (you are consuming the whole ground leaf)
some specialty Assams and Kenyan black teas
Enough about caffeine… give me the decaf teas!
Sorry to burst your bubble, but decaffeinated tea is not entirely caffeine-free. The amount of caffeine is simply reduced.
The decaffeination process removes between 94 to 08% of the caffeine. This is a dramatic reduction though! But people who are extremely sensitive to caffeine or have been advised by medical professionals to avoid caffeine should still know that decaf tea still has some caffeine.
How tea is decaffeinated
using ethyl acetate
tea leaves are steamed or soaked in water
tea leaves rinsed with ethyl acetate
ethyl acetate bonds with caffeine molecules and removes them
leaves rinsed again and dried
ethyl acetate is found in ripe fruit
using methylene chloride
similar to ethyl acetate method but using methylene chloride
great for preserving flavour
is a synthetic chemical
using carbon dioxide
tea leaves are soaked in water
tea leaves placed in a pressurised chamber with liquid carbon dioxide
carbon dioxide bonds with caffeine molecules and removes them
carbon dioxide is evaporated
cleanest, preserves most flavours
expensive
Swiss water method
tea leaves soaked in hot water
caffeine and flavour compounds extracted
water passed through carbon filter that captures caffeine but allow flavour compounds to pass through
flavour-rich, caffeine-free water is then used to decaffeinate a new batch of leaves
great for preserving flavour
no chemical solvents
usually used in coffee and not tea
Hmm.. sounds like decaf tea may taste different!
Yes, but the difference depends on the method.
Teas decaffeinated by carbon dioxide tastes closest to the original.
The other methods can cause loss in flavour to quite some extent/
The decaffeination process may also remove some antioxidants.
Why tea feels different from coffee
As mentioned above, tea drinkers often describe a “calm alertness” without feeling the jitters from caffeine. Coffee drinkers on the other hand, sometimes describe the opposite, which is a sharp energy spike followed by a steep crash.
This difference is due to the presence of L-theanine in tea. L-theanine moderates the caffeine’s impact. This is why some people can drink several cups of tea throughout the day without feeling overstimulated.
Different people react to caffeine differently
Having said all these, the way your body responds to caffeine also depends on how your body processes caffeine.
People with faster metabolism can break down caffeine more quickly, while people with slower metabolism break down caffeine much slower. Some older folks have a slower metabolism, which is why you sometimes hear your grandma saying how she had to toss and turn in bed at night after having tea at 4pm in the day.
Some people also have genetic variations that make them especially sensitive to caffeine, while others have no issues at all.
If you are sensitive to caffeine, consider starting with low caffeine teas first. Brew them with colder water and shorter steeps. Have only high caffeine teas very early in the morning.
Pouring it all together
Caffeine in tea is not as simple as “black tea has more caffeine and green tea has less”. The type of tea you choose based on its variety, the age of leaves, the growing conditions, the harvest season, and how you brew matter more.
My advice? Get your teas from reputable shops with clear descriptions of its source and its harvest.
