Here Is Why You Have a Green Poop Based on Science

Why Do I Have Green stool?

It’s not usually a subject that we like talking about, but the color and type of your stool can tell a lot about what is going on inside your body. One of the most common questions asked is why a person sometimes has green stool.

We all know that stools are usually brown in color, so when something changes, it’s only natural to be concerned. So, should you be overly concerned if sometimes you have dark green poop?

What Causes the Color of your Poop?

First of all, it’s important to know what causes the color of poop. Our stools or feces is the waste material that leaves the body after the body has used as much of the nutrients in the food as it can.

When we eat food, our digestive system starts working to break down the food to absorb the nutrients.  The liver secretes bile, which has a yellowish-green color, to digest fats.

Dr. Michael Picco on the Mayo Clinic’s website says that the bile pigments react with the enzymes in your gastrointestinal tract and change their color from green to brown.

So, the distinctive brown color of poop comes from a mixture of dead red blood cells, waste from bacteria and bile.

Sometimes, there can be changes to the color of your stool because of changes in your diet, an underlying health issue, or taking certain medications.

For example, yellow stool can sometimes be caused by the body not being able to absorb fats and this can affect people with celiac disease.

Sometimes, black tarry stools can be a sign of internal bleeding, but they can also appear if you are taking iron supplements or activated charcoal. For more information read my article on what your stool can tell you about your health.

So, what causes green stools? What are the reasons that sometimes we have them?

Causes for Green Poop

If you notice that occasionally you have dark green stools, you shouldn’t be necessarily overly concerned about it. Green poop is usually caused by a change in diet, a reaction to nutrients in your food, or a digestive problem.

Let’s have a look at the main reasons below.

Food and Diet

Dark green stools can be caused by consumption of large quantities of dark leafy vegetables like spinach, lettuce, kale, broccoli, peas and cabbage.

This is because of the large quantities of chlorophyll in these vegetables. Chlorophyll is the chemical in plants responsible for their green leaves and it has many health benefits. Because you are taking in more nutrients than the body can use, the rest comes out as waste.

Eating large amounts of black licorice can also cause dark green stools. This is because usually licorice is made using anise oil and sugar and some people have a sensitivity to anise oil which makes their poop green.

Of course, if you consume food or drinks containing green food coloring, then this can also affect the color of your stool.

Medications and Vitamin Supplements that can cause Green Stools

Iron SupplementsAnother reason you can sometimes have dark green poop is because of taking iron supplements. Although iron supplements usually turn stools black, they can sometimes cause dark green stool.

Chlorophyll Supplements – It is becoming quite popular for people to take chlorophyll supplements, and these, of course, will turn your poop green. Usually, when you stop taking these types of supplements your stools should return to their normal color.

Laxatives and Colon Cleansers – Because our stools change color while they are moving through the digestive tract, anything that speeds up this process will change the color of your poop. Therefore, laxatives and colon cleansers can cause your poop to change color because the bile which has a yellowish-green color, hasn’t had enough time to break down.

Antibiotics – Antibiotics can also cause green poop. This is because antibiotics destroy some of the bacteria in your gut and affect the digestive process. So, sometimes there just aren’t enough bacteria left in the gut to turn your poop to its ‘traditional’ brown color. To restore healthy intestinal flora, you need to do these 3 things after taking antibiotics.

Medical Conditions and Diseases

There are certain medical conditions and diseases that can cause stool to become green. For example:

Gas – Sometimes, excess gas can build up because of an imbalance of bacteria in the gut, and if that is the reason then you could have green poop. Once you have resolved this issue, your stools should return to their normal color again. For more information, please read my article on what your farts reveal about your health.

Salmonella – Salmonella infection can be caused by eating undercooked poultry meat or eggs, a lack of hygiene, or by handling reptiles or rodents. Salmonella can also be infectious and can easily be passed on between family members.

Apart from the abdominal pain and diarrhea associated with salmonella, you could also notice that your stools have become dark green.

Diarrhea – Any medical condition which causes diarrhea can result in dark green poop. This is due to the fact that solid matter is passing through the digestive systems faster than it should. Therefore, there is a higher concentration of green bile in poop because it hasn’t had the chance to break down.

Because diarrhea can interfere with the amount of nutrients the body can absorb and make you dehydrated, you should make sure to drink plenty of fluids.

You should remember that some anti-diarrheal drugs can also interfere with the color of your poop, sometimes making them yellow or black.

When diarrhea stops, your stools should return to their normal color.

Gastrointestinal Diseases that may cause Dark Green Stools

There are some chronic gastrointestinal diseases which have a side effect of having green poop. The reasons for this are similar to what has already been mentioned here: the fact that there is more bile in poop and certain supplements and medications that can make dark green poop.

Some of these diseases are:


Stress can affect your body in many ways. Stress can also cause the stool to become dark green and this is because it plays havoc with your gastrointestinal system and interferes with how your body breaks down food.

An article published by the Harvard Medical School showed that our nervous system helps to regulate digestion. If stress becomes severe, the digestive process can slow down or get disrupted causing gastrointestinal disorders.1

Once you have been able to manage your stress levels better, your stools should return to their normal color.

Green Stool – When to See a Doctor

Usually you don’t need to seek medical attention for your discolored stool. However, if you notice that you have green poop for more than a few days, you should see a doctor.

If you think that your dark green poop is because of taking iron supplements, you should talk to your doctor who can adjust your iron dose or recommend an alternative treatment.

If there appears to be another underlying medical condition, then your doctor may arrange to test a stool sample, do a blood test, and may even arrange for you to have a colonoscopy.

It is worthwhile to remember that when it comes to the color of your stools, they should be brown and not too hard or too watery. A change in color means that something in the digestive process isn’t working properly and may indicate a health issue.

You should also see a doctor anytime you notice that the green poop is accompanied by other symptoms, such as frequent abdominal pain, fever, loss of appetite, indigestion or flatulence.

Read my other related articles:
1. Here’s What Your Stool Can Tell You About Your Health
2. What Can Your Urine Tell You about Your Health
3. Here Is What Your Farts Reveal About Your Health
4. How to Make Yourself Fart on Command


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