Caffeine and Tea
Originally called “theine”, caffeine was first discovered in tea in 1827 (it was later shown that theine was in fact the same substance as the “caffeine” which had already been identified and isolated in coffee and the term “theine” was subsequently dropped). While the caffeine in tea and coffee (and, indeed, chocolate) are in all respects identical, a drinker’s experience and perception may differ between the two beverages for various reasons.
First off, let’s not ignore the power of the placebo effect: someone enjoying a cup of tea at the end of the day may be doing so in the expectation of feeling calm and relaxed, whereas the same person drinking coffee may be doing so in more stressful circumstances (e.g. at work) and expecting to feel “energised” as a result. Both these expectations may to some extent be self-fulfilling.
The effects of tea-based caffeine may also be counteracted by other constituent chemicals such as L-theanine (an amino acid which has a relaxing effect that has been noted to smooth out the “jitters” of caffeine), or antioxidants (found in large quantities in some teas, and which may slow the body’s absorption of caffeine).
In any case, although tea contains more caffeine per dry weight than coffee, even allowing for variations between types of tea, processing methods, brewing techniques etc, tea is usually brewed and served to a much weaker concentration than coffee. A typical “cuppa” tea may be made with 2 grams of dry tea, compared with 10 grams of dry coffee in a comparable cup, so the tea will contain significantly less caffeine than the equivalent volume of coffee. Indeed, a British study in 2004 looked at 200 cups prepared by consumers going about their normal brewing routines. It found that the average caffeine level in the cups of tea (black English style teas) was 40mg as against 105mg in the coffee.
The amount of caffeine in any particular tea depends on many factors, including the variety grown, whether the tea is high grown or low grown, the amount of direct sunlight received, the processing it undergoes (especially the eventual size of leaf), and how it is finally brewed. Younger leaves, higher on the plant, contain greater concentrations of both caffeine AND antioxidants than their older neighbours. Oxidation does not act to concentrate caffeine in tea, so colour (whether of leaves or their liquor) is not a great indicator of caffeine content – not only does darker not necessarily mean stronger, it doesn’t necessarily mean weaker either!
While it’s difficult (and usually incorrect) to make broad generalisations about the caffeine content of any particular tea, the following teas are notable for their caffeine “strength”:
|Relatively low caffeine
||Relatively high caffeine
||Pai White (White)
In fact, the greatest impact on the caffeine content of tea is the water temperature and length of brewing time. Black, Green and White teas have very similar caffeine contents, but a tea steeped for five minutes in boiling water will infuse a LOT more caffeine into the liquor than one brewed for only two minutes in merely hot water.
Tea can be decaffeinated by a number of methods. In the “direct method”, the tea is steamed for 30 minutes and then repeatedly rinsed with a solvent which flushes the caffeine away. The “carbon dioxide process”: involves dissolving the caffeine in carbon dioxide which is passed over the tea at supercritical pressure. In both processes, the caffeine is captured in carbon filters and recovered for later use (e.g. in soft drinks).
However, since all “real” teas come from the same plant (camellia sinensis) which contains caffeine, even decaffeinated tea is not completely caffeine-free – it may still contain 5-10 mg per cup, enough to be noticeable to a more caffeine-sensitive individual. To eliminate caffeine intake completely, one must switch to uncaffeinated infusions e.g. herbal teas and tisanes such as Camomile, Rooibos or Peppermint which are naturally caffeine free.