Life's Little Mysteries

Why Is My Poop Green?

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poop-green
Green poop is usually not a sign of a health problem. (Image credit: Brenda Carson | Shutterstock.com)

It may be alarming to see green poop in your toilet bowl, but it isn't necessarily a cause for concern.

Your poop may be green if you eat a lot of green vegetables, such as spinach and broccoli, because these foods contain large amounts of the green pigment chlorophyll.

Other dietary causes for green stool are iron supplements and green food coloring, which can be found in flavored drink mixes, ice pops and birthday-cake icing.

[5 Ways Your Poop Can Advise You on Health]

Bile — a fat-digesting yellow-green fluid that's secreted by the liver and stored in the gallbladder — can also cause green poop.

"As bile pigments travel through your gastrointestinal tract, they are chemically altered by enzymes, changing the pigments from green to brown," gastroenterologist Dr. Michael F. Picco explained on Mayo Clinic's website.

However, if food is moving through your large intestine too quickly, the bile doesn't have time to break down completely and stains your stool green, rather than brown.

Sometimes, green poop is an indication of a health issue. For example, cancer patients who undergo a donor bone-marrow transplant may develop graft-versus-host disease, which is marked by a number of gastrointestinal symptoms, including watery, green diarrhea, according to the National Cancer Institute.

Certain infections, like those caused by the bacterium Salmonella or the parasite Giardia, can also cause green stool. But other symptoms — including severe diarrhea, abdominal cramps and fever — are common with these illnesses. 

[5 Ways Gut Bacteria Affect Your Health]

In short: Green stool is typically benign and not something you need to worry about, unless it's accompanied by symptoms of other health problems.

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Joseph Castro
Joseph Castro
Live Science Contributor
Joseph Bennington-Castro is a Hawaii-based contributing writer for Live Science and Space.com. He holds a master's degree in science journalism from New York University, and a bachelor's degree in physics from the University of Hawaii. His work covers all areas of science, from the quirky mating behaviors of different animals, to the drug and alcohol habits of ancient cultures, to new advances in solar cell technology. On a more personal note, Joseph has had a near-obsession with video games for as long as he can remember, and is probably playing a game at this very moment.