Charts of caffeine levels float about the internet, showing black tea as the most caffeinated and with green tea much lower, and white tea still lower. However, many of these are misleading, at best, and completely inaccurate at worst.
While I’ve written about what affects caffeine levels, including variability in the growing, picking, production, and steeping of tea leaves, let’s look more closely at what impacts the caffeine levels of black tea.
First, why did black tea get the reputation for being the most caffeinated tea? There are a number of reasons for this, and the simplest could just be that it’s the most well-known. Another idea is that people associated the darker color of black tea with more caffeine because it reminded them more of coffee.
Looking at it more scientifically may help us determine truths and half-truths. Black tea, particularly bagged black tea, has typically gone through the CTC (cut-tear-curl) process, meaning the leaves have been shredded. With CTC there are more edges and more surface area (compared to whole leaf), which means more caffeine can be extracted in water. Bags of black tea also tend to contain more tea by weight than bags of other tea which would mean a higher caffeine level. Finally, black tea is steeped at the hottest temperature and longest time of any Camellia sinensis tea, both of which tend to extract more caffeine.
Now that we know how the myth of black tea containing the most caffeine may have developed, let’s uncover the truth.
In fact, caffeine originates in the tea plant–it acts as a natural pesticide and is concentrated in new growth, because that part is more appealing to bugs. Since black tea is typically picked from older, hardier leaves, it should have less caffeine than white tea and green tea that is picked young. (The exception to this would be a first flush darjeeling–black tea made of new growth.)
Because caffeine is a substance naturally produced by plants, everything from the cultivar to the growing location and picking season can affect the inherent caffeine amount. Therefore, even before processing, packaging, and steeping, tea leaves can have a wide range of caffeine levels.
This variance in caffeine levels has been recorded time and time again in laboratory tests. Studies published in 2005 and 2008 found a huge range of caffeine levels, even among black teas tested. Caffeine Informer, too, gives a chart showing ranges from 14 mg up to 61 mg of caffeine in black tea, depending on brand and steep time.
In the book, Tea: History, Terroirs, Varieties, the caffeine content of Matcha (powdered green tea) was recorded at 126 mg(!) making it the standout in caffeine levels by a wide margin. Regular green tea is up there, too, having upwards of 48-50 mg of caffeine depending on the tea being tested.
Suffice it to say, that you won’t be able to predict the amount of caffeine in your black tea. Likewise, it is impossible to say definitively that a given black tea has more caffeine than a green or a white tea.
The research does back up the notion that if a representative sample of black and green teas were taken, and the caffeine levels averaged out, the caffeine of black tea would likely be slightly higher than that of green tea (not including matcha).
My take is, choose the tea that you like. Sip, savor, enjoy! But if you’re sensitive and it’s close to bedtime, wait for the next morning before you down a cup of tea or two. Or three.