What causes green, watery stools?

Passing green, watery stools is commonly caused by conditions such as indigestion or acute gastroenteritis; in some cases, it results from dietary factors. When indigestion occurs, the gastrointestinal tract’s ability to digest and absorb food is impaired—sometimes leading to undigested food being excreted unchanged. So, what causes green, watery stools? Below, we address this question.

What Causes Green, Watery Stools?

1. Consumption of Green Foods

Some individuals regularly consume large amounts of green vegetables, animal liver, or animal blood—foods rich in chlorophyll or iron. These components can impart a greenish hue to stool. In most such cases, no specific treatment is required; simply adjusting one’s diet—such as reducing intake of green vegetables—can effectively alleviate the condition. Therefore, maintaining mindful dietary habits is advisable.

2. Indigestion

Many individuals with indigestion produce insufficient gastric acid, impairing normal digestion and resulting in incomplete breakdown of food. As these incompletely digested residues pass through the intestines, they interact with intestinal bacteria and may turn green. Additionally, patients with iron-deficiency anemia often take iron supplements; when these medications combine with food in the digestive tract, oxidation may occur, producing a green discoloration.

3. Intestinal Dysbiosis or Accelerated Transit

When food passes rapidly through the intestines, bilirubin does not have sufficient time to interact with alkaline substances in intestinal fluid. Instead, under acidic fecal conditions, bilirubin may oxidize into biliverdin—causing green-colored stools. Similarly, during acute gastroenteritis, intestinal contents are expelled rapidly, and harmful bacteria—including Pseudomonas aeruginosa—may proliferate, potentially leading to greenish stool discoloration.

The above outlines the main causes of green, watery stools. We hope this information proves helpful.