Does coffee make you poop?
Yes, for about 3 in 10 people. For the people it hits, coffee gets things moving within minutes of the first sip. Caffeine isn't the whole story: decaf does it for some people too, just not as hard.
Did coffee make you go?
The meter says what should happen. Your bowels get a vote too.
Why it works
It gets the colon squeezing
In gut-pressure tests, a cup of coffee got the colon moving about as hard as a 1,000-calorie meal, 60% harder than plain water.
It's not just the caffeine
In a 1990 survey, decaf set people off too. In the pressure tests decaf was weaker than regular, so caffeine adds to it but isn't the only trigger.
Mornings are the famous one
In that same survey, about half the people coffee affected said it only happened in the morning, and over half said only if they hadn't already been that day.
Sources: Brown, Cann & Read, Gut 1990; Rao et al., Eur J Gastroenterol Hepatol 1998.