Poop is normally a brown color so when the color of your poop is green, it can be a bit of a surprise.
And if this has ever happened to you, you may be wondering “why is my poop green?”
Feces is usually brown or dark brown because of two compounds: bile and bilirubin.
Bile is made in the liver and stored in the gallbladder and its job is to help with digestion (1).
Bilirubin is a compound found in the blood that is made after red blood cells break down and will travel to the digestive tract.
There it is broken down by bacteria in the large intestine and then excreted from the body through poop (2).
Your feces can change color and be green, red, black, or even have a purplish tint.
While most of the time, stool with a green pigment is a result of your diet and eating leafy green vegetables, your poop’s pigment may be indicative of something more serious.
Read this article to find out more about common causes of green poop and when you should consult a physician.
Reasons Poop Can Turn Green
1. You Ate Green Food
Green poop or dark green poop are usually the results of eating a meal high in chlorophyll-containing foods like green vegetables such as spinach and kale.
So, if you ate a green smoothie or a large green salad the day before you have green stool, chances are, this changed the color of your poop and you have nothing to worry about!
A small amount of food coloring and food dyes can also change the poop color.
For example, children and toddlers will frequently have green poop after going to a birthday party and eating green frosting on the birthday cake.
Drinking green-colored beer on St. Patrick’s Day can also cause green stool and isn’t anything to worry about.
If you drink green beer don’t be surprised if you have bright green poop the next day!
Drink mixes can also change stool color so if you indulge in fun-colored beverages, don’t be alarmed.
Certain foods contain a lot of chlorophyll and can cause a color change in poop. Some common stool colors and the food that causes it are:
- Green: spinach, kale, broccoli, green food coloring, bok choy, green peppers, as well as breastmilk and formula in infants and toddlers
- Red: beets, cranberry juice, tomato juice, Kool-Aid, red food coloring
- Pink: Pepto-Bismol, food dyes
- Black: licorice, grape juice, dark beer
- Purple: blueberries, blue food coloring, purple foods
Many new vegetarians and vegans report having green feces frequently.
This might have come as a shock to them during the first days on this diet!
Eating more fruits and vegetables and less animal products is the likely culprit.
Vegetarians and vegans are more likely to consume more leafy greens so it’s no surprise that this type of diet would cause the color of their stool to have a more permanent greenish hue.
In short, if you have the occasional green stool, it is likely due to what you ate the day before and you have nothing to worry about.
2. High-Fat Diets
High-fat diets like the ketogenic diet are very popular right now and it seems that many people are using this diet as a weight-loss strategy.
These diets involve drastically decreasing the amount of carbohydrates that are consumed while increasing the amount of dietary fatty acids up to 70% (3).
This type of diet might cause the body to create more than enough bile acids, which your body may have trouble breaking down. (4,5)
A side effect of this may be green stool and isn’t something to be worried about.
Some people report having yellow poop on this type of diet and unless it is neon yellow, you don’t have anything to worry about.
3. Coffee, Alcohol, and Spicy Foods
Coffee, alcohol, and spicy foods can have a laxative effect in your digestive system.
This means that they speed up the transit time at which food moves through the digestive tract (6,7).
When individuals consume too much coffee or alcohol, this can hinder the body’s ability to break down bile in the digestive tract.
When this isn’t broken down properly, it will travel through the digestive tract and ends up in the stool, and can change poop color to green or sometimes yellowish-green color.
Consuming too much spicy food is known to irritate the stomach and can increase transit time.
This can increase how quickly food passes through the digestive tract and cause loose stool.
This isn’t something to be super concerned with, but it is a sign that you drank either too much coffee or alcohol and you should cut back.
Having diarrhea (loose stool) can change poop color from brown to green.
This is because the body cannot break down bile as quickly in the digestive tract.
Bile is a greenish-yellow fluid involved with digestion that is made in the liver, stored in the gallbladder, and will travel through bile ducts to assist with digestion.
The purpose of bile is to help break down dietary fatty acids so that they can be absorbed by the small intestine (1).
Having loose stools can stop the body’s ability to break down bile, which can cause green, watery bowels.
Some of the more common causes of loose stool are:
- Bacterial infection/illnesses
- Inflammatory bowel disease
- Certain medical procedures (like a bone marrow transplant)
- Graft vs host disease
- Ulcerative colitis
- Celiac disease (immune reaction to eating gluten)
- Pancreatic insufficiency
- Biliary disease
- Crohn’s disease
- Some medicine
- Inflammation in the digestive tract
- Irritable bowel syndrome (IBS)
The most common cause of diarrhea is food poisoning (8).
This happens when you eat undercooked meats or food that has spoiled.
It is very common to have loose green stools or even dark green diarrhea as a result of food poisoning.
Most loose stool is temporary and will resolve without treatment in a day or two.
However, if you are experiencing long-lasting diarrhea, long-lasting green diarrhea, or bloody diarrhea, you should seek help from a medical professional because this could be a sign of a serious underlying problem.
Being prescribed a course of antibiotics is another potential cause of a green bowel movement.
Antibiotics are a type of prescription medication that are used to treat bacterial infections.
The most common infections treated with antibiotics are respiratory tract infections and urinary tract infections (9).
Antibiotics are only prescribed to treat bacterial infections (not viral infections) and work by killing the bacteria or by preventing their ability to reproduce.
Unfortunately, antibiotic medication cannot isolate and affect the “bad” bacteria in the body.
This means that when taking an antibiotic, it is also going to affect some of the “good” bacteria in the intestine.
This will decrease the number of bacteria that normally break down bilirubin, causing stool discoloration, meaning your stool may not be its normal brown color.
If given antibiotic medical treatment, you can help to restore your gut microbiome by making small dietary changes.
Make sure you consume prebiotics, which are high-fiber foods like legumes, whole grains, fruits, and vegetables.
Supplementing your diet with probiotics like yogurt, kefir, and sauerkraut also helps.
Certain supplements can also cause green stool. Some of the possible causes are:
- Iron supplements (can also cause black stool)
- Green tea
If you recently started consuming one or more of these, don’t be surprised if your stool looks green.
Take a look at your daily multivitamin because some of them also act as an iron supplements.
If you are unsure if a supplement is the cause of a change of color of your stool, stop taking it for a few days and see if your stool color returns to its normal, brown color.
If it doesn’t, you may want to seek medical care.
When to Be Concerned
A change in the color of your stool can also be a side effect of a more serious condition.
Some of the most common conditions include celiac disease, diverticulitis, Crohn’s disease, and ulcerative colitis.
Important signs to look out for include:
- Presence of blood or bright red blood in stool
- Red stool (not caused by red food)
- Yellow and oily stool
- Pale or white stools
- Consistent constipation
- Consistent diarrhea
- Anal tears
- Chronic hemorrhoids
How often you have a bowel movement and the size of it are also important.
Colon or rectal disease are both a serious cause of small and frequent bowel movements.
Excessively large bowel movements can be a sign of right colon disease (8).
If you have any of these symptoms and also and have a fever, itchy anus, and/or nausea, please see a doctor right away.
Serious Conditions that Cause Green Stool
Even though most of the time green feces isn’t something to be worried about, there are some cases when it can be a sign of a more serious condition.
Health conditions that are known to change the color of your stool include:
- A bacterial or parasitic infection (salmonella, norovirus, giardia are common)
- Celiac disease
- Ulcerative colitis
- Inflammatory bowel disease (IBS)
- Gut dysbiosis (more “bad” bacteria than “good” bacteria in the gut)
- Gallbladder disease
- Fissures (anal tearing)
- Gastroenteritis (inflammation in the gut)
- Bleeding in the gut
- Host disease
If you have been diagnosed with any of the above medical conditions, your bowels may be a different color as a result.
If you haven’t been diagnosed with any of the above medical conditions and you haven’t made any changes to your diet that you think would cause green stool, you should discuss this with your doctor.
Is Green Poop a Sign of Cancer
Cancer is a tricky disease because symptoms can be so different between patients.
While it is true that cancer can change the color of your stool, it usually will not change the color of stool.
With cancer, black stool or tarry stool is more common, and red stool can represent bleeding in part of your intestine. It can also be a sign of a tumor (10).
This doesn’t mean you should ignore the color of poop.
If you have green stool accompanied by other symptoms like nausea or vomiting, fatigue, major digestive discomfort or irritation, constipation, a persistent stomach ache or stomach pain, and reoccurring diarrhea, then speak to your doctor.
When to Call the Doctor
A green bowel movement alone isn’t a reason to be worried and isn’t a sign of a more serious condition.
As mentioned above, there are reasonable explanations like changes to your diet, iron supplements, food poisoning, and dyes that can all cause your stool to turn a green color.
You should be concerned if you experience green diarrhea for more than three days.
Long-term diarrhea is usually a sign of an issue with your digestive system and can cause dehydration and a loss of nutrients, which can cause other health issues like a temporary malabsorption disorder.
If you believe you might have a parasite infection because of raw meats, you will want to contact your doctor.
In addition, if you have green stool along with nausea, extreme fatigue, black poop, abdominal pain (different from menstrual cramps), constipation, or fever, make an appointment with your primary care physician.
These could all be a sign of infection, an issue with the gastrointestinal tract, or another medical condition.
Lastly, if the color of your poop is red or white, you should seek medical help.
When people think of a bowel movement, they think of something brown or dark brown, but sometimes, it can be green.
Green poop in adults is normally the result of a change in the diet and shouldn’t alarm you. Many people who eat lots of green, leafy vegetables have green poop the next day and this is completely normal.
However, if you are experiencing green diarrhea or constipation for more than three days, or if you notice a drastic change in the texture of your stool, contact your doctor.
- Hundt M, Basit H, John S. Physiology, Bile Secretion. StatPearls [Internet]. StatPearls Publishing; 2020 [cited 2021 Aug 21]; Available from: https://www.ncbi.nlm.nih.gov/books/NBK470209/
- Kalakonda A, Jenkins BA, John S. Physiology, Bilirubin. StatPearls [Internet]. StatPearls Publishing; 2020 [cited 2021 Aug 21]; Available from: https://www.ncbi.nlm.nih.gov/books/NBK470290/
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