What are the causes of green feces?

Written by rose kivi
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Various medical conditions and dietary foods can alter the colour of faeces. Although green faeces may look scary, it is most often harmless. Usually green faeces is not a cause for concern and is simply caused by dietary intake. When green faeces is accompanied with other medical symptoms or is persistent, a doctor should be seen.


Sometimes breast-fed and formula-fed infants eliminate green faeces. In the absence of other symptoms, it is quite normal and is a response to eating a liquid diet or a baby formula that contains iron. Green faeces that is accompanied with yellow skin, skin rashes or constipation may be caused by jaundice or food allergies and warrant a trip to the doctor's office.


Most cases of green faeces are caused by food items that we ingest. Eating a lot of green vegetables or a lot of foods that contain green food colourings causes green faeces. In food-related green faeces, once the perpetrating foods are eliminated from the bowels, faeces return to a normal colour.


Ingesting large amounts of supplements can turn the faeces green. The most common supplement culprit is iron. The body cannot process large amounts of iron, so the body excretes iron salts to eliminate the excess amounts. Iron salts colour the faeces green. Other supplements that can turn faeces green are chlorophyll and green algae. When supplements are discontinued or lower amounts are ingested, faeces return to a normal colour.

Rapid Transit

Faeces that travel through the digestive system faster than normal often come out green. The green colour is attributed to the green colour of bile. In normal digestion, the liver excretes bile to aid in the breakdown of fats. As the bile and faeces travel through the intestines, enzymes change the colour of the bile from green to brown. If faeces travel through the digestive too rapidly, the enzymes do not get the opportunity to react with the bile and green faeces is the result. Some of the causes of rapid bowel transit are allergies, Celiac disease, digestive upset, GERD, lactose intolerance and some bowel disorders. Occasional green faeces is generally not a cause for concern and is most likely caused by digestive upset. If green faeces is present often, a trip to a doctor is warranted.

Bowel Disorders

Bowel disorders that cause faeces to travel through the digestive system rapidly sometimes result in green faeces. Irritable bowel syndrome and ulcerative colitis are two examples of bowel disorders that cause rapid bowel transit.

The colour of bile is altered by enzymes in the small intestine. If the small intestine has been surgically removed or if there is a condition that causes inflammation in the small intestine, green faeces can result. Inflammation in the small intestine is often seen with Crohn's disease.

Infectious Gastroenteritis

Infectious bacteria and viruses cause rapid bowel transit, which leads to green faeces. Common infectious culprits are giardia, salmonella and rotovirus (stomach flu).

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