Poop color probably isn’t something you think about very much—until you look down in the toilet and something seems off. We’re used to seeing various shades of brown in different consistencies, but what if the color is something unexpected? The color of your poop can give clues about different aspects of health, or it might simply be a temporary change based on something you recently ate. What if it’s green, though? What does green poop mean?

What Does Healthy Stool Look Like?

While the color of your stool is an important consideration, the size and consistency are also aspects worth evaluating. One way to get clarity is by referencing the Bristol Stool Chart, a classification system developed by doctors that indicates what healthy human feces should like when a person’s digestive system is functioning normally. The Bristol Stool Chart is arranged on a scale from more hard and dry to more soft and loose:

  • Type 1: Separate hard lumps, like nuts (hard to pass)
  • Type 2: Sausage-shaped, but lumpy
  • Type 3: Like a sausage but with cracks on its surface
  • Type 4: Like a sausage or snake, smooth and soft
  • Type 5: Soft blobs with clear-cut edges (passed easily)
  • Type 6: Fluffy pieces with ragged edges, a mushy stool
  • Type 7: Watery, no solid pieces, entirely liquid

    Based on the chart, “normal” stool should be type 3 or 4: smooth, sausage-shaped, and relatively easy to pass. Types 1 and 2 are harder and dryer, and they tend to suggest constipation. On the other end of the spectrum, watery, loose stool tends to suggest diarrhea. In terms of color, normal, healthy stool should be a shade of brown. This brown color comes from the pigments in bile and bilirubin, two compounds secreted into the digestive tract that help break down the foods we eat.

    What Do Other Colors of Poop Mean?

    Looking at the size and consistency of stool can help highlight any problems with motility and whether or not bowel movements are regular. Color changes, on the other hand, may be a function of what we’ve eaten recently or an indication of a problem with our digestive system. Below are some other stool colors and what they might mean:

    • Black: Black stool can sometimes be caused by something you ate that has a dark food dye added to it like black licorice. It may also be the result of taking iron supplements or using bismuth subsalicylate (Pepto-Bismol) as an antacid. Black and tarry stools may also indicate bleeding in the upper gastrointestinal tract.
    • White: Stool that is white or clay-colored typically indicates a lack of bile. Bile, which has a yellow-green hue, is produced in the liver and held in the gallbladder until it is released into the small intestine. If there is blockage (for instance by a gallstone) in the biliary duct, that would show up in the stool. A blockage like this is a serious medical condition that requires rapid medical attention.
    • Yellow: If the stool is yellow, it is also likely greasy and has a foul odor; this is most likely due to a high amount of fat in the stool that comes from dietary sources. It might also be yellow for someone with celiac disease who eats too much gluten.
    • Red: The two main reasons for red poop are something you ate or bleeding in the GI tract. Red food coloring or foods like beets or Jello could be the culprit. If you know you haven’t eaten anything and the stool is bright red, it could indicate bleeding in the large intestine; by contrast, dark red stool could indicate bleeding the upper GI tract.

    Common Causes of Green Poop

    It’s important to note that seeing a different color in the toilet doesn’t necessarily mean there’s a big health problem. For most people, color and consistency vary every day. It’s when patterns emerge (apart from something you regularly eat) that you may want to take notice. As for when stool is green, there are a number of possible causes:

    • Green food: The most likely cause of green poop is green food, whether naturally green or because of green food coloring. All green vegetables contain chlorophyll, a compound found in plants that gives them a green pigment and allows them to absorb energy from sunlight. Surprisingly, some foods that aren’t even green (like blueberries) have pigments that still can appear green by the time they’re processed and make it through the large intestine.
    • Gastrointestinal problems: Irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD), which includes Crohn’s disease and ulcerative colitis, are two gastrointestinal health conditions that sometimes cause increased bowel motility. This means that bile moves through the colon too quickly; since bile is normally reabsorbed by the body, increased motility can cause excess bile to be present in the stool and cause a greenish tint.
    • Medication: Some medications, especially antibiotics, can interfere with the normal function of the beneficial bacteria in the colon. The resulting imbalance can then change the color of the stool. Also, the same way that iron supplements can turn stool black can also make it appear dark green.
    • Infection: Becoming infected with a virus like norovirus (a common cause of gastroenteritis), a bacteria like Salmonella, or a parasite like Giardia can have a similar effect on motility as IBS and IBD. The increased motility leaves excess bile in the stool that can appear green.

      When to See a Gastroenterologist

      You certainly don’t need to worry at the first sight of green poop. Most causes of green poop are either totally benign or not serious. If, however, you have been experiencing symptoms or changes to your bowel habits in addition to seeing a different color in the toilet, it might be time to speak with a gastroenterologist. At Cary Gastro, we are dedicated to providing excellent digestive healthcare so that you can have peace of mind and maximum quality of life. If you’d like to speak with someone about your symptoms, please contact us to request an appointment.