"Another possibility is that the colonic response to coffee could be mediated by exorphines. Both regular and decaffeinated coffee contain exorphines that can bind to opiate receptors. Opiate receptors, both in the brain
and within the gut wall, mediate important effects on colonic motility'0; Sun and his colleages" have shown that opiate receptors are necessary for the colonic response to food." (From Brown infra)
I completely agree that coffee is also an adaptogen through other mechanisms than caffeine effects.