"Ritheann an bia tríot."
Translation:The food runs through you.
I work with a skinny lad who has a big appetite and the way he puts it is that the food goes straight through him (meaning he eats a lot without putting on weight).
So the phrase has a non-diarrhoea meaning too.
I happen to know a person whom the diarrhea most certainly applies to.. and most disturbingly they don't exactly keep it a secret!
Technically we have food decomposed in our blood - aminoacids, vitamins, fat, carbonhydrates so on. So the food is flawing through us.