Poop can turn green for many reasons, such as a diet rich in high chlorophyll plants. Other possible causes include antibiotic use and bacterial infections.
Poop is generally brown, but, at times, it can turn green, red, black, yellow, or any color in between. Many of these color changes do not signal a medical condition, but some can be signs of something more serious.
This article discusses poop color, what it can mean, and when to speak with a doctor.
Green stool is usually the result of eating a large quantity of leafy, green vegetables. This is because chlorophyll in the plants produces a green color. Alternatively, a person might have green stool after eating artificially colored foods, such as frosting from a cake.
Certain foods in a person’s diet are the most common causes of green poop. However, people who do not eat a lot of greens or food coloring should be aware that green poop can have a more serious cause.
Possible causes include:
- Bile pigment: Green stool
can result from the presence of bile pigment. If food moves too quickly through the intestine, bile pigment cannot break down sufficiently. One potential cause of this is diarrhea. - Antibiotics: Antibiotics can change the types of bacteria present in the gut. Because bacteria influence the color of poop, a change in bacteria may mean a change in stool color, often to green.
- Certain medical procedures: For instance, a person whose body rejects a bone marrow transplant may develop graft-versus-host disease. Diarrhea and green stool are symptoms of this condition.
- Parasites and bacteria: Certain pathogens can cause poop to turn green, such as the Salmonella bacterium, the water-based parasite Giardia, and norovirus. They can cause the guts to move food more quickly, affecting stool color.
People who think their green stool is not the result of a diet rich in vegetables or green food coloring should discuss it with a doctor.
Stool is usually light to dark brown. A substance from red blood cells called bilirubin ends up in the intestines. Bacteria break it down and it turns stool brown.
Changes in diet can produce varying stool colors. Eating beetroot, high chlorophyll green vegetables, or licorice can significantly change stool color. Drinking dark stouts or drinks that contain dyes, such as flavored drink mixes, can have a similar effect.
In infants, foods may cause color changes, including the following:
- Green: spinach, breast milk, formula
- Red: beetroot, tomato soup, cranberry juice, other red drinks
- Black: licorice, grape juice
However, some causes of non-brown stool are more serious, and it is important to talk with a doctor about these issues immediately.
Health conditions that may change the color of stool include:
- anal fissures, or tears in the lining of the anus
- gallbladder disease
- celiac disease
- ulcerative colitis, a condition causing colon inflammation
- Crohn’s disease, a condition in which all layers of the small and large intestines can become inflamed
- cancerous tumors in the gastrointestinal (GI) tract
- cancers of other digestive organs
- diverticular disease, a condition in which pouches form in the large intestine
- bacterial or parasitic infections, such as Salmonella or Giardia
- piles, also known as hemorrhoids
- bleeding in the gut
It is difficult to consistently relate a precise color to each condition. However, here are some possible connections between colors and conditions:
- Reddish or maroon: This can be a sign of bleeding somewhere in the GI tract.
- Yellowish, greasy, smelly: This can indicate an infection in the small intestine. It could also be a sign of excess fat in the stool due to a malabsorption disorder such as celiac disease.
- White, light, or clay-colored: This can indicate a lack of bile in the body, possibly from a blocked bile duct.
- Black or dark brown: This can be a sign of bleeding in the upper GI tract, such as the stomach. Alternatively, it could be the result of iron supplements or bismuth subsalicylate.
- Bright red: Bleeding in the lower digestive tract, such as the rectum or anus, may cause bright red stool. Hemorrhoids and anal fissures may also cause bright red stool. Alternatively, red stool may be due to consumption of red food coloring, cranberries, beetroot, tomato-based products, or red gelatin.
- Green: Large quantities of green dye or green vegetables, antibiotics, or a GI tract infection may cause green stool.
If any discoloration persists, it is important that a person contacts a doctor instead of trying to work it out on their own.
The more serious possible causes of stool discoloration include conditions such as diverticulitis, Crohn’s disease, ulcerative colitis, and cancer, which usually manifest with bleeding from the lower GI tract.
Important symptoms to look out for include:
- dark, tarry stools
- red or maroon stools
- large amounts of blood passed from the rectum
- blood in the toilet bowl
- an itchy anus
- swollen blood vessels in the rectum
- small tears in the skin of the anus
- an urge to keep passing stools even when the bowel is empty
- anal fistula, or a small channel that develops between the distal end of the large bowel and the skin near the anus
In addition to any traces of blood in the stool or bleeding from the anus, a person should pay attention to any other symptoms that occur with stool discoloration. These may include nausea, vomiting blood, or a feeling of fullness.
A person should seek the advice of a doctor immediately if any of these symptoms persist.
Common causes of rectal bleeding
- piles, also known as hemorrhoids
- inflammatory bowel disease
- anal fissures
- anal fistula
- gastroenteritis, which is inflammation of the gut
- diverticular disease
- bowel cancer, such as small intestine or colorectal cancer
It is worth having a quick look at the stool before flushing it away. Stool is a very good indicator of whether the digestive system is working correctly. It may provide a clue to illnesses such as those mentioned above.
According to the Bristol stool chart, there are seven shapes and consistencies of human stool. Each one suggests something about a person’s diet or body.
The Bristol stool chart
- Type 1: separate, hard lumps, similar to nuts, which are often hard to pass
- Type 2: sausage-shaped but lumpy
- Type 3: sausage-shaped but with cracks on the surface
- Type 4: sausage- or snake-like, smooth and soft
- Type 5: soft blobs with clear-cut edges that are easy to pass
- Type 6: fluffy, mushy pieces with ragged edges
- Type 7: watery with no solid pieces — entirely liquid
As a general rule, type 3 or 4 is the ideal stool, as it is easy to pass but not too watery. Type 1 or 2 means that a person is probably constipated. Type 5, 6, or 7 indicates that a person probably has diarrhea.
This chart helps doctors identify problems and correlate the time food takes to pass through the digestive system. The shape and form of stool may also help doctors make a diagnosis.
Learn more about the Bristol stool chart.
Here are some frequently asked questions regarding poop turning green.
Is it OK to have green poop?
There are many reasons why poop may turn green, including illness or changes in diet. If any discoloration persists, it is important that a person contacts a doctor instead of trying to work it out on their own.
What is green poop a symptom of?
Green poop can be a symptom of changes in diet, taking antibiotics, having certain illnesses or parasites, or bile pigment.
The most important thing to do to regulate stool color is to eat a nutritious, balanced diet. The ideal stool color is light to dark brown. Some people who eat large quantities of green foods may pass green poop.
Having green poop is not usually a cause for concern. However, it is important to keep an eye on both the color and the texture of stools. Anyone with concerns about the color of their stool should discuss them with a doctor.