I think I’ve finally figured out the longtime mystery about why tea both wakes me up and calms me down (anxiety-wise). I consistently feel a physical effect after drinking a cup of tea, as if a knot inside my stomach dissolves, and problems don’t seem quite as pressing, and it’s easier to be friendly and sociable. This sounds like the opposite of caffeine, which is known to increase irritability.
But just recently, I stumbled on a possible explanation. It’s not the caffeine at all! It’s something called L-theanine:
“Theanine is able to cross the blood-brain barrier and appears to have psychoactive properties. [...] it appears to increase levels of the inhibitory neurotransmitter GABA, and to a lesser degree, dopamine.”
L-theanine is often mentioned in conjunction with green tea, but it is also found in black tea. This article says green tea has about 8 mg per cup, while therapeutic doses of the stuff (for anxiety disorders) are more like 200-600 mg. Another source indicates 15-30 mg per cup, and that “L-theanine increases the production of dopamine and serotonin, two brain chemicals associated with alertness, pleasure, and a good mood.”
Further, there’s evidence of a lack of side effects (at least in rats):
“In 2006, a study conducted on rats administered super-high doses of L-theanine daily for a 13 weeks found no consistent or significant negative effects on behavior, food intake, body weight, clinical chemistry, urine, blood, morbidity or mortality.”
Therefore, I should be free to experiment away. And if theanine is the active agent, then I should get the same mood benefits (though not the wake-me-up effect) from decaf green tea. If only it were easier to do controlled experiments on oneself!