One of our quirks as a species is that we think our food is bland if it doesn't have enough poison in it.
(thelemmy.club)
actually, mountain streams are mostly safe because the water is in constant movement, and also as it's on a mountain, that typically means that the source is not that far away and so the water didn't have a lot of time to stand around and get infected with all kinds of stuff.
slowly-flowing or standing water in the plains is what gives you the diarrhea of your life.