How appropriate of the timing to talk about caffeine at this hour?! I am wide awake at the moment from 5 teas I had earlier today. I am tired but can't fall asleep.
So how much caffeine is there in tea? I have seen lots articles comparing coffee and tea. Many of my customers told me they can't drink black tea because it keeps them up, so they want to switch to green tea. The usual question starts: how much caffeine is in tea? Tea has less caffeine than coffee right? Does black tea have more caffeine than green? Does white tea have the most caffeine?
Any of the comparing pairs are like apple to orange, kiwi to bok choi, bamboo to aloe vera, just pick any 2 strange things you can think of.
The caffeine level in any tea has little to do with the type of tea. As a tea leaf from a tea tree, the caffeine level is determined by the varietal and the soil it is in. For example, a TGY bush grows in Anxi might have different caffeine content from a same TGY varietal grows in Wuyi. A Huang Zhi Xiang varietal has more caffeine than Yu Lan Xiang varietal on the same hill. An old bush has more caffeine than its young clone. Lao Ban Zhang has more caffeine than a Yiwu. The difference is by varietals, not by type. Not all green teas have more caffeine than black, not all oolongs have less caffeine than white.
Caffeine level can vary from 2.5% to 6.5% before processing. This holds true across the board from white to black. From a leaf on a tree to consumption ready, caffeine level will change by processing and storage. Unless scientists take lab samples of every single varietal on earth for research, and farmer/sellers post that information on a label, we can not say how much caffeine does one tea contain. Even if that's done, chemicals of the trees will change as they grow. It's irresponsible to say green tea has so and so much caffeine as a whole category as seen in a million article online and in magazines. There is no definite formula for tea, it's not science like pharmaceutical drugs.
Impact of caffeine can vary from person to person also. While one person will stay up till dawn, the same tea will put an other person to deep sleep. I have heard caffeine will make people with ADD tired and sleepy. Drinking tons of low caffeine level teas will keep you up more than drinking a little bit of the high caffeine level tea. 20 tea bags to make one pot of tea will send me through the roof for sure.
I advice my clients to take small amount at the beginning and recommend teas according to their previous tea experience.