It can be alarming to suddenly notice that your poop is looking a little… green. But there are a variety of reasons this could be the case, and not all of them are dangerous

After looking in the bowl, think back on what you’ve been putting in your mouth lately. You’ll most likely find the answer in what you’ve been eating. But there are also some other causes of colorful stools:

  • an underlying medical condition
  • antibiotics
  • a bacterial infection

The usual brown color of excrement is due to a leftover mix of dead red blood cells and waste from the bacteria in your bowels. The bile in your intestines is usually a yellowish-green color, but bacteria add the rest of the hue. Besides making your poop brown, bacteria perform vitally important functions, like helping you to absorb nutrients from your meals.

Feces can be a different color when food doesn’t spend enough time in your digestive tract. This can happen if you have diarrhea. In that case, the contents of your intestines rush through the process too quickly to allow healthy bacteria to give your poo its characteristic hue.

The most common reason for green stool is a dietary habit or change. Food that can cause green stools include:

Dark green vegetables and green powder supplements contain chlorophyll, the chemical that allows plants to make energy from the sun. Eating a lot of them can turn your poop green, but that doesn’t mean there’s something wrong. Keep eating those greens!

Some foods contain food coloring that doesn’t get processed properly. This can also leave a colorful residue in your stool. So if you wake up after a St. Patrick’s Day spent imbibing green beer and notice something off when you go to the bathroom, you probably just need some water.

The food coloring you consume doesn’t necessarily have to be green in order to make your poop green. Purple, blue, and black dyes may also lead to green poop. For example, in 2015, fast food chain Burger King went viral with posts from individuals who had purchased their Halloween Whopper which had a black bun. Many people who partook in the Halloween Whopper reported that it turned their poop green after eating it.

Bile is a fluid made in your liver and stored in your gallbladder. This fluid naturally has a green-yellow color. When bile combines with foods you eat, the bile helps your body break down more fat from the diet. This allows more fat to be absorbed into your body in the small intestine.

However, your body must break down bile so it can be excreted as waste. Normally, this is accomplished by traveling a pathway through your intestine. Sometimes when you have diarrhea or other digestive issues, bile can’t be broken down as quickly. The result can be poop that appears green in tint because of the natural green color of bile salts in your body.

If you’ve recently been prescribed antibiotics, especially a strong one, the medication can kill off large parts of your gut’s normal bacteria. This decreases the population of the brown-staining bacteria in your lower intestine. Probiotics, such as yogurt or kombucha, can help restore balance to your intestinal flora.

Several other medications and supplements can also cause a breakdown in pigments that turns your stool green. One example is iron supplements.

Parasitic, viral, and bacterial invaders can also be causing your green stool. Yes, your body already contains billions of bacteria that serve a vital purpose. Outsiders, however, can wreak all sorts of havoc on your intestinal output.

Bacteria like Salmonella (the common culprit behind most food poisoning), the water parasite giardia, and norovirus can cause your guts to flush quicker than normal, which can lead to green-tinged stools.

If you have Crohn’s disease or another GI condition, bile may move through your intestines too quickly, causing green poop. Crohn’s disease is a bowel disease that causes inflammation in the digestive tract.

Celiac disease, which is an intolerance to gluten, causes a variety of GI problems, such as gas, bloating, diarrhea, and stomach pain. If you have diarrhea or loose stools with celiac disease, you may also have green stools.

Other possible causes of green stools include irritable bowel syndrome, ulcerative colitis, and overuse of laxatives, since all of these issues can cause rapid bile movement through the intestines.

Anal fissures are small tears in the tissue lining your anus, and are often the result of passing a hard stool. But these tears can also develop if you have chronic diarrhea or inflammatory bowel disease. So if you have an anal fissure related to diarrhea, you may notice green stools.

Fissures can also cause bright red blood in your stool.

Don’t panic or imagine the worst if you have green stools. It’s true that different-colored stools can be a sign of a cancerous tumor. But with cancer, stools are often a black or tarry color. This typically indicates bleeding from somewhere in the upper GI tract. Additionally, sometimes bright red blood occurs in lower GI tract cancers.

Although green stools aren’t usually a cause for concern or a sign of cancer, you shouldn’t ignore green poop that’s accompanied by other symptoms.

If you have other symptoms, such as recurring diarrhea or vomiting that doesn’t improve, this can indicate another serious medical condition. Talk to your doctor ASAP.

If you’ve experienced diarrhea for more than 3 days, seek medical care. Long-term, untreated diarrhea can lead to dehydration and poor nutritional status.

If your chronic green stool is accompanied by more severe symptoms, such as stomach upset, blood present in the stool, or nausea, these symptoms also warrant a doctor’s visit.

While the nature of the visit may be awkward to discuss, a doctor can review your medication list, diet, and other medical conditions as a means to determine potential causes of chronically green stool.

If you experience green stool as a one-off symptom, it’s highly unlikely to be cause for concern.

However, seeing other colors in your stool may indicate an issue. Bright red signifies potential bleeding in the lower intestines. A black or dark tarry brown could indicate bleeding in your upper GI tract. But remember, it could also be the blueberries or black licorice you had at lunch.

If you’re diagnosed with a medical condition, preventing green poop starts with addressing the underlying problem. For example, avoid foods like gluten that trigger diarrhea if you have celiac disease.

In most cases, occasional green stools are nothing to worry about. Long-lasting bouts of discolored stool may signal something more serious, but a one-time occurrence usually just means you’re eating your vegetables.

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