I know what you're saying. I've been thinking about that subject a lot recently. I've been trying to figure out what it is about tea that has that effect, since it seems to be completely unrelated to the caffiene content.
Did you know that Tea has an incredibly high Vitamin C content? That only one fruit (Guava) has more Vitamin C?
Green tea is the best for it.. in fact here's a wuote from www.greentealovers.com
"Sencha contains significant Vitamin C (250mg per 100g). Fermented teas (black, oolong tea) contain far less because vitamin C dissolves in the fermentation process."
Did you also know that Vitamin C is one of the chemicals that is extremely important to proper brain functioning?
Check out this site for a pretty exhaustive and accesible description of Vitamin C:
Apparently there have been studies that correlate increased Vitamin C intake to increased IQ test scores (not that I really accept the IQ test as a standard of intelligence.. but you know.. science does it's thing...)..
Also, and this will cross over a little into the "smoking green tea" territory, but there's some street knowledge about Vitamin C. People who are seriously into doing hallucinagenic drugs, such as LSD, mushrooms, X, or pot, know that if you drink a ton of Orange Juice or ingest other Vitamin C laden foods/drinks/tablets, you will not only have more intense effects from the drugs, but also not suffer the negative physical and mental side-effects of those drugs the next day (or next week depending on how many hits you drop
). Apparently one of the dangers of doing too much LSD is that it drastically reduces the pooled Vitamin C levels in your brain, due to the increase brain activity during the effect of the drug.
So, it follows that by increasing your Vitamin C intake, through whatever form (tea, oranges, tablets, guava, strawberries, etc..) you'll notice an increase in mental clarity and alertness.
I have always noticed this same effect when eating or drinking items with a lot of Vitamin C.
Well, anyway, those are just my personal observations, and I haven't seen or heard of any studies that have looked into tea's Vitamin C content directly increasing brain activity on a short term basis, based on the amount contained in a cup of tea.
Getting into more details... There are 250mg of Vitamin C in 100g of green tea. A single serving (multiple infusions) of tea is generally made from 5-10 grams of loose tea leaves, meaning that per change of leaves your intake of Vitamin C is about 10-12.5mg, which is about a 1 percent increase in the "normal" standing pool of Vitamin C in your brain (1500mg). This is assuming that you have managed to extract all of the Vitamin C through the brewing process. I have no numbers available about what percentage of the actual content of Vitamin C in the tea leaves is extracted through normal brewing. It might not be a full 100 percent.
I'm not sure if .5-1% of your brains standing pool of Vitamin C would be enough to have noticeable psychoactive effects or not. It certainly can't hurt!
I think more likely, that most people have too little Vitamin C in thier diets, and that by drinking tea, it may increase the suffering level to a more manageable level, and THAT may be quite noticeable. A body suffering from a Vitamin C deficiency has many problems, including sluggish brain activity, messed up brain chemistry levels (since Vitamin C is responsible for assisting the release of various chemicals (such as Seratonin) into the brain), and it is also necesary for the formation of collagen, the agent which binds cells, so a lack of C can just simply cause a ton of problems. Even a minor relief of those problems, in a suffering body can seem like a miracle, and the amount in tea might be enough to do that.
Hope that helps,