Assam HalmariThe mythology about caffeine in tea rivals the Greek pantheon. A lot of people have gone into chemistry labs with a supply of tea to attempt to figure out what’s going on in these leaves and they’ve come out with a lot of information, and everyone siezes their favorite piece and flings themselves into the argument with zeal. After careful research, I have determined that most of the information floating around out there is actually perfectly consistent, it just sounds like it isn’t when you’re having a good time arguing. So! I’m going to write down how it seems to line up to me, and see if it makes any more sense written down together like that.

How much caffeine is in tea?

The basic answer to “how much caffeine is in tea?” is that black tea has half the caffeine of coffee, and oolong has less than black, green less than that, and white less than that. This seems logical, and you drink a cup of black tea and you do feel less stimulated than after a cup of coffee and more than after a cup of green tea, so either it’s right or the placebo effect is in full force. Except there are a lot of people who insist that all types of tea have the same amount of caffeine, and some people will tell you that there’s less caffeine in coffee than in tea, and there’s more caffeine in tea buds than in full grown leaves so white tea ought to have the most caffeine, right? Right!?!Ti Kuan Yin

Leaves and Water

First, it’s important to be precise here. There is more caffeine in tea leaves than in coffee grounds, but there’s more caffeine in a cup of coffee than in a cup of tea. More coffee grounds are used for each cup of coffee than tea leaves for each cup of tea, and because coffee is more finely ground, more of the caffeine is extracted in the brewing process. Roughly the same problem plagues us when we ask how much caffeine is in each kind of tea. Not only are black teas more likely to be cut up into small pieces than other kinds, but they’re also brewed with hotter water. That means more caffeine in your drink! The hotter the water is, the more caffeine is in the final drink. So tea buds can have all the caffeine they like, but unless someone pours boiling water all over defenseless delicate white tea leaves, the final white tea drink is not going to have as much caffeine as black tea does. So if you want tea with less caffeine in it, brew it with cooler water.

What’s in a leaf?

Long Jing (Dragonwell)Another imporant thing to remember is that absolute amounts are not as relevant as percentages. I know, that’s not a very informative sentence, but bear with me, I’ll explain. When a tea leaf is picked, it has a certain amount of caffeine molecules in it, and those molecules are pretty much going to sit around playing poker and chatting until you plunge the leaves into hot water. I mean they aren’t going anywhere, not breaking down or anything. But during oxidation other parts of the tea leaf break down and condense until that caffeine makes up a much larger part of the resulting black tea leaf. So it’s not so much that green tea has less caffeine, it’s that it has more other compounds. I think. I’m going to admit that I’m not entirely sure of this stuff, because I can’t find a study that addresses this exact question, so this is just what I conjecture from what information I can find. Anyone else out there know more about this?

Other factors

Now, there are a lot of other things that have some effect on caffeine content, including, but not limited to: particle size (how finely the leaves are cut up), varietal (assamica has more than the basic variety), position on the plant (buds and new leaves have more than old leaves), the soil the plant grew in, the altitude, whether the plant was grown from a cutting or a seedling, how the plant was fertilized, and what time of year the leaf was picked. These have smaller effects, though, so unless you feel moved to hire private investigators and send them over to Asia with detailed spreadsheets to fill out, it isn’t worth your time to worry about them.Silver Needle

In the end, the black>oolong>green>white hierarchy does hold up. Water temperature is a major reason for this, and I’m pretty sure there’s something going on with the chemical composition of the leaf, but I need my own lab to make sure, and I’ve got a small teahouse and a laptop. Brew your teas at the recommended temperature, and you’re set.

Elizabeth, Teahouse Kuan Yin staff

A few links with more detailed information:

Oxidation and Fermentation in Tea Manufacture is an excellent explanation of oxidation.

Caffeine and Tea focuses primarily on debunking the myth that a brief initial steeping gets rid of most of the caffeine, but it’s full of data that’s both carefully collected and can tell you a lot of different things about caffeine and tea.

The Wikipedia article on caffeine and the Britannica one both help you understand caffeine enough that the explanations of what it does in tea make more sense.