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This question arose from my personal experience - after quitting coffee, I switched to drinking tea ( a lot of tea ). One day there was no tea, and I had a terrible headache, similar to the first days without coffee. A friend of mine suggested there is more caffeine in black tea than in coffee, and suggested green tea.

This made me wonder: how much caffeine is there in the average tea bag, as opposed to two teaspoons of grain coffee ? How about caffeine contents of other tea varieties ( green, white ) ?

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Black tea contains caffeine but less than coffee (~50-60% of it). Of course if you drink a lot more tea than previously coffee you can consume the same amount or more of caffeine. – Martin Scharrer Jun 2 '11 at 15:14
up vote 18 down vote accepted

Comparing the caffeine in a cup of tea with a cup of coffee (both brewed, prepared with tap water) on average:

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Bear in mind that these values values vary wildly according to where you look. The above data is averaged from a large number of sources, available here.

So, surprisingly, no. Brewed coffee generally has more caffeine than brewed tea. However, dry tea contains more caffeine than dry coffee (source) but since we don't usually eat dry coffee or dry tea leaves, it is safe to say your friend is wrong about caffeine content but right to suggest green tea as an alternative. Green tea contains around 25mg per cup.

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The values depend hugely on how you brew the tea (bound or unbound form caffeine?) and to a lesser extent on how you brew the coffee. I’m not really happy with such blanket values that don’t respect this variation. – Konrad Rudolph Jun 2 '11 at 11:58
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@Konrad: they also depend heavily on what coffee and tea you compare. Just for example, Robusta coffee beans have ~2-3 times the caffeine content of Arabica beans. ico.org/botanical.asp – user2046 Jun 2 '11 at 16:28
    
A tea cup is often much larger than a coffee cup. I don't know how Wolfram Alpha handles this. – dancek Jun 3 '11 at 10:39
    
@dancek, if I'm not mistaken, US cups ( 0.2366L ) are used for both tea and coffee [ link ] – Mihai Rotaru Jun 3 '11 at 12:12
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There is another effect that matters a lot and that is how fast the caffeine is absorbed by the body. With coffee it is pretty fast but tea contains a complex mixture of things like polyphenols that slow up the rate of caffeine uptake, so you get a gentler high. Even if you brew strong tea like a british builder. – matt_black Oct 30 '11 at 20:56

It totally depends on the type of tea, the amount of leaves you use. The average tea bag contains about 2 grams (about a tablespoon) of tea. If you're making loose leaf tea, it's possible you're adding more than that, resulting in a higher caffeine content.

Tea generally has less caffeine than coffee. Black teas are generally the strongest, ranging from 20-70 mg of caffeine per 8 oz (although I have one on my shelf that contains a whopping 110 mg per serving), whereas brewed coffee generally contains 90-150 mgs of caffeine per 8 oz, though can be more if you brew it strong. Green and white teas usually have less caffeine content than blacks, almost always under 45 mg per 8 oz. Herbal and red teas are naturally caffeine free. (Mayo Clinic Caffeine Chart)

I would expect that, when switching from coffee to tea, you've been drinking more tea than you drank coffee. Tea, in my experience at least, goes down easier than coffee, and doesn't give you the same, uh, stomach issues coffee can. Drinking more would mean more caffeine, which could be the reason you're still suffering from caffeine withdrawal headaches. Switching to green or white teas could be a good compromise, just be careful to track your intake.

If you like the routine of drinking hot beverages all day and still want a bit of caffeine, you can blend black or green teas with herbals or reds to "dilute" the caffeine content. You can either do this with loose leaf tea, or making a large thermos of tea at once with two teabags (generally, use one teabag per 8-12 oz of hot water). I recommend mixing Earl Grey and lavender.

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