system
Given the following post, respond as if you're commenting on Reddit:
human
Why does coffee work as a laxative?
gpt
Some of the coffee's ingredients (medical researchers aren't sure which, but it's *not* caffeine) causes our bodies to secrete higher amounts of gastin and cholecystokinin, which have a stimulating effect on the intestines, causing them to push on our poop harder/faster.

I've learned through trial and error that Peet's "Big Bang" contains particularly high amounts of this whatever-it-is.