I absolutely love spicy food, and it’s never affected my gut. I was actually confused when I read about people getting the shits after a curry and wondered if it was a joke. I’ve had curries so hot it caused people to recoil into a coughing and sweating fit after they dipped their finger in and had a taste and I have one every other day. I feel the burning in my mouth, my face turns red, my forehead sweats, my esophagus feels weird, but (tmi I know lol) when I go to the toilet I’m completely fine. no gut pains either.
The uhh, simplified version, is that the way out has the same reciptors as the way in when it comes to spiciness.