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.
Most people have taste receptors in their gut as well as on their tongue. It helps regulate how quickly your muscles contract to move stuff along through your intestine.
Some people don’t have as many, and some people build up a tolerance to capsaicin (in both their mouth and gut).
Capsaicin trigger nociceptors, tricking the brain into believing you’ve hurt yourself. It’s not a flavour.