Does tea have caffeine? Absolutely!
Every tea brewed with leaves from the tea plant (Camellia sinensis) always contains caffeine, but the amount of caffeine in tea depends on much more than just the type of tea you choose.
The real science behind tea and caffeine challenges the myth that caffeine content is determined by tea type, and that black tea always has more caffeine than green tea.
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Around the world, we drink tea for both its taste and for how it makes us feel. In tea, caffeine works together with L-theanine, EGCG and more for a nuanced and unique effect unlike any other beverage in the world.
That’s why understanding a tea’s caffeine level is just one of the first steps to understanding how tea affects us. To really get a full picture of how caffeine works in tea, we first need to know how a tea was farmed, when it was picked, and how you’ll brew it.
"Every tea brewed with leaves from the tea plant always contains caffeine."
Does all tea have caffeine?
Caffeine is nature’s most widely-consumed stimulant, increasing blood flow, heart rate, and general alertness. The tea plant (Camellia sinensis, L. Kuntze) naturally produces caffeine as a defense against insects, and tea’s stimulant effect was used even in ancient times as a meditation aid for monks' early morning rituals.
Until recently, we thought caffeine alone was responsible for the alertness and clarity you get drinking tea. Now, we know brewed tea contains a complex combination of caffeine, the related stimulants theobromine and theophylline, and the counterbalancing effect from L-theanine and antioxidants. Caffeine alone can cause a jittery feeling, but in tea, the jitters are usually missing thanks to this complex balance.
Take note! Measuring caffeine content in tea (or any brewed beverage) requires specialized lab equipment and serious expertise. Because the caffeine content of tea can vary so widely - from tea to tea and from season to season - it is difficult to estimate the specific mg per cup of any specific harvest.
Take any advertised caffeine content of loose leaf tea with a grain of salt. These are often just general estimates that have not been confirmed by food scientists.
What Factors Play a Role in Caffeine Content?
Caffeine content is not defined by tea type. Black tea, green tea and more can all be made from the very same plants. Caffeine content cannot be increased through tea processing, so tea leaves picked to the same standard at the same time and place will have the same caffeine content, regardless of how they have been processed.
Which teas have the most caffeine? Here are the determining factors:
• The tea leaves:
1st picking small buds and leaves grown in the shade produce tea leaves with the most caffeine
• The water temperature:
Hotter water extracts more caffeine. Cooler water extracts less. Brew with boiling water for the most caffeinated tea.
• Tea size and quality:
Small crushed particles common in tea bags infuse more caffeine faster than whole leaf tea because there is surface area for diffusion
Tea produces caffeine to fight off insects and natural challenges. A biodiverse environment stimulates more caffeine production than monoculture farming
Caffeinated Tea: The Breakdown
Once we understand what affects tea's caffeine content, we can make informed decisions to find the most and least caffeinated tea and brew style for each tea type. Let’s cut past the common myths and look at where each tea really stacks up for tea caffeine levels.
How Much Caffeine in Black Tea?
• Black tea’s caffeine range:
as low as 14 mg per cup for larger leaf, cooler brews
and as high as 61mg per cup for young pickings and hot brews
Black tea has a reputation for being the most caffeinated tea. The old thinking was, the darker the tea, the more the caffeine. It turns out that black tea’s reputation as a high caffeine tea is only observed when the tea is brewed at higher temperatures and with smaller leaf material (crushed tea bag dust).
If you are looking for higher caffeine tea, you can still reach for black tea. There are many small, early harvest buddy black teas out there (like Jin Jun Mei and more). Look for early harvest, small leaf teas growing with biodiverse competition. Many black teas also stand up well to full-boil brew temperatures for the maximum caffeine.
How Much Caffeine in Oolong Tea
• Oolong tea’s caffeine range:
between 14mg and 61mg per cup, depending on brew temperature and growing conditions
Oolong tea is one of the most diverse tea types, with countless growing regions and finishing techniques. The caffeine content in oolong can vary just as much.
On the one hand, oolong tea is generally made with larger, later season tea leaves. In general, larger leaves and more mature leaf material contain less caffeine than an younger, small buds harvest from the same plant.
On the other hand, high-quality oolong teas grow in tremendously biodiverse microclimates like Daping village in Anxi or the Wuyishan Ecological Preserve. Biodiversity can stimulate more caffeine production, as can shady (misty mountain) growing conditions.
Finally, oolong loves to be brewed at a full boil, which guarantees a higher caffeine extraction than the same tea brewed cold.