Green stools in adults, infants and children

Green stools that appear accidentally are usually not a cause for concern. However, if green feces are persistent, accompanied by other symptoms such as abdominal pain, diarrhea, fever, a health problem should be ruled out.

Most often, stools become green due to excessive consumption of green leafy vegetables, taking iron supplements, certain medications, or due to diarrhea.

What color are stools and what is it determined by?

Normal stool color is usually light to dark brown. It is due to the bile pigments urobilin and stercobilin.

Bile is a yellow-green liquid produced by the liver and stored in the gallbladder. When eating, it enters the small intestine, where it helps digest fats. When passing through the intestines, bile pigments change color due to chemical reactions, turning from green to brown pigments. Under the action of bacteria in the small and large intestine, bilirubin glucuronide, which has a yellow-green color, turns into urobilinogen and stercobilinogen. In the large intestine, they are oxidized to urobilin and stercobilin, which are excreted in the feces, giving them their specific brown color.

Causes of green stools

Here are some of the most common causes of greenish stools:

Dietary reasons

• green leafy vegetables and fruits

Dark green leafy vegetables and green fruits are rich in chlorophyll, a pigment that gives plants their green color. Consuming large amounts of these vegetables and fruits can change the color of the stool to green.

Here are examples of foods that can cause green stools: spinach, kale, broccoli, arugula, celery, asparagus, avocado, green olives, kiwi.

Nuts such as pistachios, seeds such as hemp seed and herbs such as parsley, basil and coriander are also rich in chlorophyll. Matcha, a type of green tea powder, can also make stools bright green.

• food colorings

Foods and drinks with artificial green dyes, such as some candies, ice creams, cake frostings and drinks, can also stain the stool green.

• foods rich in iron

Eating foods high in iron or taking iron supplements can change the color of the stool from dark green to black.

Rapid passage of food through the intestinal tract

When food moves too quickly through the intestinal tract, the bile pigments do not have enough time to break down completely. The presence of yellow-green bile pigments in the feces can lead to green stools.

Here are some reasons for rapid intestinal transit:

Consumption of coffee, spicy foods

Coffee and spicy foods have a laxative effect that makes food move faster through the intestinal tract.

Diarrhea

With diarrhea, the motility (movements) of the intestines is increased and the risk of the appearance of green feces increases. There are many causes of diarrhoea, for example:

• infectious diarrhea caused by salmonella, shigella, escherichia coli, giardia, norovirus
• antibiotic-associated diarrhea – also known as pseudomembranous colitis
• inflammatory bowel diseases – Crohn’s disease, ulcerative colitis, diverticulitis
• irritable bowel syndrome
• lactose intolerance
• celiac disease
• mushroom poisoning, chemical substances
• excessive use of laxatives.

Gallbladder problems

• gallbladder obstruction

The presence of gallstones or a gallbladder tumor can obstruct the bile ducts and affect the flow of bile and its release into the intestines, potentially leading to green stools.

• gallbladder removal

After the gallbladder is removed, bile goes directly from the liver into the intestines. As a result, diarrhea may occur. This problem can occur recently after a cholecystectomy, but the diarrhea usually goes away within eight weeks as the body adjusts.

Medications that cause green stools

Taking some medications can cause greenish stools. Such drugs are, for example:

• antibiotics – some antibiotics, such as ciprofloxacin, can disrupt the balance of gut bacteria, causing stools to change colour.
• Laxatives – cause food to pass through the intestines quickly, preventing the complete breakdown of bile.
• anti-inflammatory drugs, for example indomethacin
• supplements containing chlorophyll.

Causes of green stools during pregnancy

Green stools are common during pregnancy and are usually nothing to worry about. They are most often due to:

• taking iron supplements or prenatal vitamins and minerals that contain more iron
• increased intestinal motility due to stress and anxiety.

Causes of green stool in babies and children

A newborn’s first stool is called meconium. They have a dark green to black color. Meconium contains intestinal epithelial cells, bile, mucus, swallowed amniotic fluid. The newborn passes meconium in the first 24 to 48 hours.

Green colored stools in babies and children can be due to:

• mother’s diet

Increased consumption of chlorophyll-rich foods by the mother can cause the infant’s stool to turn green.

• some adapted foods

Some formula milks fortified with iron can give the baby’s stools a green tint.

Sensitivity to milk proteins, digestive enzyme deficiencies, or carbohydrate malabsorption can also cause green stools in formula-fed babies.