After my morning constitution I wondered, for the millionith time, why is poop brown? What exactly is my body doing that leaches all the color out of what I eat…except for brown?
I eat a red apple, brown poo. I eat a bright yellow cake…still brown poo. So whats going on in there?
http://www.straightdope.com/classics/a2_381.html
Cecil speaks.
ahh…I did a search for poo…or poop. Should have known Cecil wouldn’t be so vulgar 
Thanks Uncle!
Oddly enough, if you eat ground glass your poo will be black!
Once I ate a Cookie Monster cupcake with blue icing, and my poop was as green as a healthy lawn.
If you eat fresh beets (not canned or pickled) you can have bright red poop. Scared my daughter to death. She was sure she was bleeding internally.
If you eat enough you’ll pee reddish too.
May I suggest you never have the Shrek Slurpee.
The new colored goldfish crackers also give poo a nice bright red color.
Makes for a disturbing diaper changing experience, I’ll have you know.
Black licorice will give you a nice black turd & turn the toilet water green
WAY TOO MUCH TMI BELOW!
A barium enema (used to provide contrast on an x-ray of the large intestine) will turn any poop that arrives in that area afterwards an odd white color)
My fellow (male friend) campers on a 3rd grade trip though it was rather interesting. I for one was a bit confused untill I figured out why it was so.
-Butler
Hyena poo is a chalky white due to the high bone content of their diet.
I don’t get to work that into conversations nearly enough.
Wait, huh?
Do I want to know how you know this?
Also if you eat enough tropical punch Now and Laters.
Happily, I remembered this SD column when my 4-yo daughter asked about this last week!
Ground glass or anything else that would cause bleeding high in the gastrointestinal tract would lead to black, tarry stools.
Ah. So the specific use of ground glass in your example is a red herring.
Hm… What color would eating red herring result in?
Shrek cereal (which was green) turned the 5 year old’s output purple. He was terrified and insisted I inspect.
He went back to Cheerios with relief.
Actually, this discussion reminds me of a few years ago, when a good friend of mine decided that there were not enough blue foods in the world.
So, he started dyeing his food with blue food coloring. Blue in the batter yielded blue pancakes. Blue soaked into asparagus very well. Everything he ate had blue in it, and he probably went through a cup of food coloring in the day.
The side-effect was science. He’d heard someone state that the, ahem, “cycle” took about a day, which seemed too long for his experience. Sure enough, eight hours after breakfast… blue. Not mildly, either. It looked like a giant smurf had been there.
Well, Winny the Pooh is brown because he’s made of pooh.
Bluuuuue Moooonnn Of Kentucky, won’t you Keep On Shinin"…