If green tea has caffeine in it, then why does it make me sleepy?!
Answers: I don't think it's from crashing because it doesn't happen when I drink coffee.
As mentioned, tea contains many different chemical compounds beyond caffeine. Theanine, which is present in tea, does indeed seem to increase GABA production (the neurotransmitter involved in the sedative effects of alcohol and drugs like valium).
However, the amount of both theanine and caffeine, in tea, are relatively low. The caffeine concentration is typically a fraction of that of coffee.
With that said, the temperature of the beverage may well play a bigger role. You'll ingest the drink at 100+ degrees F, easily above your body temperature. When you eat and drink, blood concentrates around your digestive organs (aka, your "gut" or "viscera") to absorb nutrients.
You therefore have less blood in your brain and central nervous system, which is why you often feel tired after a big meal. In addition, your blood is absorbing large quantities of heat. Water carries massive amounts of heat very effectively.
Because your body needs to stay at precisely 98.6 degrees, it responds by slowing your metabolism (heat production). This compounds the "relaxed" feel.
Compare that to drinking cold water. Drink enough of it, and you'll definitely feel the shivering (increased metabolism/heat generation).
It's trendy to talk about plant phytochemicals, and they are no doubt at work in tea. But the fact that chamomile, lavendar, and various other teas seem to relax is arguably explained largely by their temperatures at consumption.
Coffee, on the other hand, contains very significant amounts of caffeine, theobromine, and other stimulants. This is why it's relaxing to initially have your morning coffee, but the relaxation soon gives way to stimulation.
It peps me up but coffee makes me sleepy.
Seriously! Peoples bodies are different I guess.
It could be you're so conditioned to the amount of caffeine in coffee that the amount in green tea has no effect. Still drink it though; it's good for weight loss (I swear!!) and has some stuff in it that researchers are saying fights cancer.
because green tea (as well as white tea) contains Theanine. It boosts the alpha brainwaves in your brain and makes you more relaxed. Green tea also contains caffeine, but if you need to be awake, tea will keep you up. Tea is awesome like that.
http://en.wikipedia.org/wiki/Theanine
because you really need to rest, even you drink tea it won't help