Coffee. Yes coffee. Do you really "feel a difference"? Instead of pointlessly debating whether caffeine affects our body (which it does of course), I want to know whether you really "feel a difference" when you drink coffee. Does it prevent you from sleeping? Can you stay concentrated on your studies for a longer time/and or later at night? I really love coffee for its taste, I drink 1 strong and big coffee (about 350 ml) per day at least, yet I feel absolutely nothing. I don't feel it perturbs my sleep or make it touger to reach. It takes me generally over 2 hours of laying in my bed before I get to find sleep, no matter if I drink a coffee just before sleeping. I don't feel it helps me to keep concentrated for a longer time when I study, etc. I know my heart beat is very likely faster after drinking a coffee but apparently that's not something I can notice, unless of course if I'd measure it with a chronometer. On the other hand I can feel a difference if I drink a 200 ml glass of beer at 4% alcohol.