Spicy food has been eaten from time immemorial in hot countries, because hot pepper kills pathogenic bacteria, in this regard, the peoples of India, Korea and many other countries in which they prefer wit have practically no problems with the gastrointestinal tract!
Because the connection between spicy food and gastrointestinal diseases is greatly exaggerated. Moreover, spicy food reduces the likelihood of peptic ulcers and bacterial intestinal infections.
This was observed in Mexico, where children are given hot chili (in the form of sweets and yogurt) almost from the cradle. As adults, they already get so used to spicy foods (their body adapts) that they can no longer live without chili (and add it to a variety of products: from sweets and drinks to sour milk products with chili). It was funny to watch the dinner, how adults are sitting all red with tears in their eyes, crying, but still endure and continue to eat this chili)) while it is extremely rare for Mexicans to have problems with the digestive system. I think the Koreans are the same. Over time and over the years, their bodies gradually adapted to spicy food and therefore does not cause any stomach ailments, etc. Unlike peoples, in whose national cuisine there is no spicy, the body is not prepared and therefore reacts painfully.