Why is it that we've let natural body function become 'gross?' I think I have a pretty open mind about most, probably because my maternal grandmother was so free with talking about bodily functions.
When you juice an orange, there's leftovers. That's all it is - leftovers. The body takes what it wants (suppose to take what it needs, but sometimes doesn't), and dumps the rest. It's that simple and natural.
I have more problems with pus than I do with poop... and I know it's just the byproduct of a body trying to take care of itself.
It's important to look for changes - i.e. one reason Lola pointed out.