Why Is Poop Brown?

WHY? is our attempt to answer all the questions every little kid asks. Have a question? Send it to why@mentalfloss.com.

If you eat, you poop! Let’s talk about eating first. When you eat, the saliva (suh-LIE-vuh) in your mouth breaks down the food using enzymes. When you swallow, the food travels down a long, soft pipe in your chest called the esophagus (e-SOFF-uh-GUS). It leads to your stomach, which is shaped like the letter J. Your stomach uses gastric (GAS-trick) acids to digest or break down the food so your body can take the parts it uses. Then, it moves into long tubes called your small and large intestines, into your colon, and out through your anus—and hopefully, into the toilet! 

Now let's talk about poop! There’s a lot of stuff in your poop that your body can’t digest, absorb (like a sponge does), or doesn't need. There is water, fibrous (FY-brus) parts of food, bacteria, fatty acids, and old red blood cells from the liver that are in an orange-brown substance called bilirubin (BILL-ee-RU-bin). Bilirubin mixes with more yellowy stuff from the liver called bile. Just like when you mix a lot of paint colors together, when you mix all this together, the result is brown. Sometimes poop is a dark chocolate brown, sometimes it’s a light sandy brown. Every once in a while, it comes out a different color.

Food comes in all kinds of colors, but poop usually comes out brown. Yet some foods can turn your poop a different color! If you eat a beet, which is dark pink to red, your poop might turn a little purple. Healthy green leafy vegetables like spinach or kale can turn it green. If you have a tummy ache and your body produces extra mucus (myoo-kus), the pale, jelly-like stuff can make your poop look lighter in color. Most of the time, however, your poop won’t surprise you. No matter how many colors of the rainbow you eat, it will mostly come out brown.

For more about how food moves from the mouth to the rear, visit KidsHealth's Your Digestive System.