This article is the first of a three-part series.
In his excellent book, A History of the World in 6 Glasses, Tom Standage selected the six beverages that he felt had the greatest influence on the development of human civilization. Three of the six contain alcohol; three contain caffeine. Tea was one of the six.
Is it the caffeine that has made tea one of the most popular beverages in the world? The flavor? Its relaxing effects? I think that without caffeine, Camellia sinensis would be just another of the hundreds of plant species that taste good when you make an infusion or tisane out of it. Perhaps yerba maté would be the drink that challenged coffee for supremacy in the non-alcoholic beverage world.
“Caffeine is the world’s most popular drug”
The above quote opens a paper entitled Caffeine Content of Brewed Teas (PDF version here) by Jenna Chin and four others from the University of Florida College of Medicine. I’ll be citing that paper again in Part II of this series. Richard Lovett, in a 2005 New Scientist article, said that 90% of adults in North America consume caffeine on a daily basis.
But yes, caffeine is a drug. It is known as a stimulant, but its effects are more varied (and sometimes more subtle) than that. It can reduce fatigue, increase focus, speed up though processes, and increase coordination. It can also interact with other xanthines to produce different effects in different drinks, which is one reason coffee, tea, and chocolate all affect us differently.
Tea, for example, contains a compound called L-theanine, which can smooth out the “spike & crash” effect of caffeine in coffee and increase the caffeine’s effect on alertness. In other words, with L-theanine present, less caffeine can have a greater effect. See a great article from RateTea about L-theanine here.
Even though Part II of this series is the one that dispels myths, I really need to address a common misconception right now. First, I’m going to make sure to define my terms: for purposes of this series, “tea” refers to beverages made from the Camellia sinensis plant (the tea bush) only. I’ll refer to all other infused-leaf products as “tisanes.” Okay, now that we have that out of the way:
“All tea contains caffeine”
Yes, I said ALL tea. The study I mentioned a couple of paragraphs ago measured and compared the caffeine content of fifteen regular black, white, and green teas with three “decaffeinated” teas and two herbal teas (tisanes). With a five-minute steep time, the regular teas ranged from 25 to 61 mg of caffeine per six-ounce cups. The decaf teas ranged from 1.8 to 10 mg per six ounce cup.
That’s right. The lowest caffeine “regular” tea they tested (Twinings English Breakfast) had only 2-1/2 times the caffeine of the most potent “decaffeinated” tea (Stash Premium Green Decaf).
There are two popular ways to remove caffeine from tea. In one, the so-called “direct method,” the leaves are steamed and then rinsed in a solvent (either dichloromethane or ethyl acetate). Then they drain off the solvent and re-steam the leaves to make sure to rinse away any leftover solvent. The other process, known as the CO2 method, involves rinsing the leaves with liquid carbon dioxide at very high pressure. Both of these methods leave behind some residual caffeine.
(As a side note: I’m not a fan of either process. When I don’t want caffeine, I’d much rather drink rooibos than a decaf tea. I only have one decaf tea out of over 80 teas and 20 tisanes at my tea bar, and I’m discontinuing that one.)
This is why tea professionals need to make a strong distinction between the terms “decaffeinated” (tea that has had most of its caffeine removed) and “naturally caffeine-free” (tisanes that naturally contain no caffeine such as rooibos, honeybush, and chamomile).
“Coffee has more caffeine than tea”
Almost everyone will agree with the statement. For the most part, it is true, assuming you add some qualifiers: The average cup of fresh-brewed loose-leaf tea contains less than half the caffeine of the average cup of fresh-brewed coffee. In the seminar, Tea, Nutrition, and Health: Myths and Truths for the Layman, at World Tea Expo 2012, the studies Kyle Stewart and Neva Cochran quoted showed the plain cup of fresh-brewed coffee at 17 mg of caffeine per ounce versus the plain cup of fresh-brewed tea at 7 mg per ounce (that’s 42 mg per six-ounce cup, which agrees nicely with the numbers from the caffeine content study I quoted above).
Interestingly, though, a pound of tea leaves contains more caffeine than a pound of coffee beans. How can that be? Because you use more coffee (by weight) than tea to make a single cup, and caffeine is extracted more efficiently from ground-up beans than from chunks of tea leaf. Tea is usually not brewed as strong as coffee, either.
At another 2012 World Tea Expo seminar, A Step Toward Caffeine and Antioxidant Clarity, Kevin Gascoyne presented research he had done comparing caffeine levels in dozens of different teas (plus a tisane or two). The difference between Kevin’s work and every other study I’ve seen is that he prepared each tea as people would actually drink it. For example, the Bai Mu Dan white tea was steeped 6 minutes in 176-degree water, while the Tie Guan Yin (Iron Goddess of Mercy) oolong was steeped 1.5 minutes in 203-degree water. Matcha powder was not steeped per se, but stirred into the water and tested without filtering.
The results? Caffeine content ranged from 12mg to 58mg for the leaf teas, and 126mg for the matcha — which is higher than some coffees.
In our next installment, I’ll look at the myths regarding caffeine in tea, including what kinds of tea have the most caffeine and how you can remove the caffeine at home all by yourself — or can you?