Here is a good article that explains it. Interestingly coffee promotes the urge to poop in at least one-third of the population and tends to impact women more than men.
Only coffee does this to me though. It's got to be a combination of things. I know coffee is higher in caffeine than most other drinks, but I sometimes take a caffeine pill, which is even higher, and it has never caused the coffee shits.
Yip mine too. I don't know why, coffee makes me feel like my bowels are gonna explode. But I still drink it, only I water it down a lot (my tummy can't handle it). If I don't drink it, I get get severe headaches, and I need the caffeine to help wake me up. Some people say it's the hot water, hot water can be a stimulant for your guts. But by the time I add water, it's pretty tepid so I think it might be the acid in it that's upsetting to my GI tract.