Yes, questions arise!! Good thought provoking article - and I hope it is "research provoking too", but I won't hold me breath because mainstream medicine probably wants to ignore this news about the human body.
So maybe the enteric nervous system comes into play once again. We do not hear much about this "other nervous system" nearly enough, despite the fact that it controls so much of our mental and physical being.
Or is this something to do with the gut FLORA? [as in, do the gut flora produce the gut seritonin? or isn't it that simple?]