Here are ten proven (or at least documented) things attributed to coffee, some of which you might not have known.
I knew it has an "effect" on my digestive system but didn't know that laxative effect is caused mainly by the stimulant, or that the effect is often so fast that it can't be attributed to the caffeine alone.
I also didn't know that it can heighten the effect of pain relievers. Unless you drink to much and get a headache. I knew about that part.