What Causes Green Diarrhea and What to Do About It

Occasional green stool (green poop) is nothing to panic about. Most of the time, there is a simple explanation for it. Eating certain foods or supplements can turn poop green.

However, there could also be a medical reason for passing green stool. A viral infection or another stomach bug can cause loose stools that have a greenish hue. Green diarrhea can also be due to a problem with digestion.

This article discusses the different causes of green stool and when you should talk to your doctor if you have it.

causes of green diarrhea
Verywell / Joshua Seong

Food or Supplements

There are several non-medical reasons for stool to appear green. Passing one solid, green stool is nothing to be concerned about. Green diarrhea may also be within the range of normal stool.

If you experience green stool, try to recall what foods you have eaten or what supplements you have taken over the past several days. Even if the food was not actually green, it could explain it. The following foods and supplements can cause green stool:

  • Eating green foods: The first and most obvious reason for a stool to be green is from eating green foods. Green leafy vegetables contain chlorophyll, a green pigment which could be coloring the stool. Green food coloring is also a common reason for stools to be green.
  • Eating purple foods: Foods with dark purple coloring, such as Kool-Aid, popsicles, and gelatin (Jell-O), can also result in greenish or green stools.
  • Iron-rich food or supplements: Iron supplements or iron-rich foods can give stool a green tinge. If an iron supplement is causing too much digestive distress (such as bloating or constipation), talk to a doctor about switching supplements.

Green Stool Around the Holidays

One of the biggest times to see green stools is during holidays when green food dye is commonly used:

  • Christmas
  • Easter
  • St. Patrick's Day

Green food coloring can take a day or two to pass through your system, so you might not connect the dots at first.

Eating unfamiliar foods at holiday meals also can cause looser stools, especially if the food is high in fat.

A green stool might not appear for a day or two after eating green foods, and by then it is easy to forget what was eaten.

Medical Causes

A viral infection can cause green diarrhea, sometimes along with vomiting. Viral gastritis (inflammation of the stomach) usually passes in a few days, and while uncomfortable, it's not usually something to be concerned about.

Consult your doctor when green diarrhea can't be explained by a food source or a virus that causes vomiting and diarrhea. It's not common, but green stool can be a sign of a medical condition.

Healthy stool tends to be brown with some variation in shade. Bile (a substance that helps digest fat) is secreted in the first part of the small intestine and is actually green. As stool continues through the digestive tract and passes through the large intestine, the bile becomes darker brown.

If the stool is still green by the time it comes out, it could mean that it went through the large intestine too fast to be turned brown. This is known as "rapid transit" or "decreased colonic transit time."

This is especially true with green diarrhea rather than a full-formed stool. Food that is moving so quickly through the digestive system will not spend a long enough time in the large intestine for water to be absorbed, resulting in a loose stool.

Green Stools in Infants and Children

Green stool is a normal occurrence in breastfed infants, especially in the first days after delivery, and is no cause for alarm.

In infants, stools will gradually change to yellow and brown as the baby approaches their first birthday and more varied foods are added to the diet.

For formula-fed babies, green stool may continue for several months. This is likely due to the iron content of some formulas.

In addition, giving an infant or a child an iron supplement (as is commonly recommended by pediatricians) may also cause green stools.

Some parents say their children have green stools while teething. There is no scientific evidence to support this common observation, however.

In older children, green stool could be food-related or due to eating non-food items, such as crayons.

If your child has swallowed or eaten a non-food object, call Poison Control at 1-800-222-1222.

When to Call a Doctor

There are some situations in which green diarrhea can be a sign of a more serious problem. You should call your doctor if:

  • Diarrhea continues for more than three days.
  • Diarrhea is accompanied by severe pain and stomach cramps.
  • Diarrhea is accompanied by vomiting for more than 24 hours.
  • There are signs of dehydration, such as dry skin, mouth, and lips, and decreased urine output.
  • There have been other changes to your bowel habits in addition to green diarrhea.

Summary

Green stool is unusual but not typically something to worry about. 

The most common cause of green stool is diet. Eating green, blue, or purple foods is often the culprit—especially items prepared using food dyes. 

A viral infection usually causes green diarrhea. This is likely the case if other symptoms are present, such as vomiting, stomach cramps, fatigue, or fever. 

Green diarrhea on its own that lasts for more than a few days or comes and goes could be a sign of a digestive issue. 

Call your doctor if diarrhea lasts longer than three days or is accompanied by vomiting for more than 24 hours. 

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Article Sources
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