Photographed by Mike Garten.
It’s the question that has been plaguing Google search engines basically ever since Google search engines became a thing: "Why is my poop green?"

It’s a valid concern, and if you’re feeling weird about inspecting your the contents of your toilet, don’t. "It’s good for people to look at their stool, and I encourage them to look at the color and the consistency, and so on,” says Robynne Chutkan, MD, an integrative gastroenterologist.

Thankfully, she says the potential explanations for green poop are mostly harmless.

The main reason for green poop is actually pretty simple — and it could even be a good thing. “If you eat a lot of deeply pigmented green leafy vegetables, like spinach and kale and so on, it’s normal for your stool to actually have a green tinge,” Dr. Chutkan says. So if you’ve ingested a lot of leaves, or even anything with a lot of green food coloring (like Jell-O), that’s likely the cause of lawn-colored number twos. And if that’s the case, it won’t stay that way forever, Dr. Chutkan tells us. Your stool will probably return back to its usual shades of brown pretty soon after that first trip to the bathroom.

Another reason for green stool could be that your food is traveling too quickly through your system. If your food doesn’t have time to digest, according to Dr. Chutkan, the bile doesn’t have time to break down as it goes through your intestine, which can sometimes cause it to remain green once it hits the toilet. This usually isn't dangerous if it's a one-off occurrence, as it typically happens when you get diarrhea from eating something — such as raw fish, expired food, or dairy (if you're lactose intolerant) — that didn't react well with your body. Diarrhea decreases the amount of time it takes for food to travel through your bowels, so that stool doesn't get a chance to turn from green to brown. If you're having a bout of food poisoning that's turning your poop green, it's probably a good idea to take an antidiarrheal like Pepto Bismol.
But when is green poop actually a cause for concern?
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If you’ve been feeling unwell, and it’s been going on for more than a few days, it could signal something slightly more serious, says Dr. Chutkan. If your green stool comes with symptoms like constant diarrhea, cramping, gas, abdominal pain, or bloating, you'll want to see a doctor — you could have a stomach bug. If your stool is loose instead of solid, and you’re losing weight or feeling feverish, definitely get it checked out. Dr. Chutkan says these symptoms may be due to a stomach infection or even a parasite.

So if you’re pooping green every day, that's when you'll have to see a doc. But if it’s a one-time thing, you probably don’t need to worry.
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