In fact, caffeine - is poison

The caffeine in a cup of coffee that you drink for courage, for many years "developed" by plants as a defense against insects. Effects of caffeine on the human by blocking certain receptors in the brain and other organs, which causes the processes by which produce adrenaline. Adrenaline released into the blood, increasing the number of heart rate and raises blood pressure.

As for insects, the effect of caffeine paralyzes and kills them. So we can say that your invigorating cup of coffee - something like a liquid fly swatter. By the way, although caffeine is not considered a poison to humans in large doses (10 grams), it is deadly.

via factroom.ru