Observing changes in stool color can be surprising and prompt questions about underlying dietary factors or internal processes.
Understanding Poop Color
Stool is typically brown due to bile and bilirubin, a yellowish substance that forms when red blood cells break down. Bile, a fluid produced by the liver and stored in the gallbladder, starts out with a yellowish-green color. As bile travels through the digestive tract, enzymes and bacteria chemically alter its pigments from green to brown. The speed at which digested material moves through the intestines, known as transit time, significantly influences this color transformation.
Probiotics and Green Poop
Probiotics introduce beneficial microbes into the gut, which can sometimes lead to green stool. This occurs because probiotics influence the gut microbiome and how bile acids are metabolized. Certain probiotic bacteria, such as Lactobacillus, possess enzymes that alter bile acids’ chemical structure. This alteration in bile processing can contribute to a green appearance.
Probiotics can also impact gut motility, leading to faster transit times for digested food. When stool moves through the intestines more quickly, bile has less time to fully break down and change color. This accelerated passage means the green pigments from bile may remain visible. Green stool after starting probiotics is generally a temporary and harmless adjustment as the digestive system adapts. Temporary diarrhea, common when first introducing probiotics, can also contribute to green stool due to rapid transit.
Other Factors for Green Poop
Beyond probiotics, dietary intake is a common reason for green stool. Consuming large amounts of leafy green vegetables like spinach, kale, or broccoli, which contain chlorophyll, can lead to green stool. Foods with blue or purple pigments, as well as artificial food dyes found in certain drinks or candies, can also result in green stool. These pigments pass through the digestive system and can impart their color.
Certain medications and supplements are another potential cause of green stool. Iron supplements are known to sometimes turn stool dark green or even black. Some antibiotics can disrupt the natural balance of gut bacteria, which can alter stool color. Medications containing bismuth subsalicylate, like Pepto-Bismol, or certain laxatives can also contribute to a green appearance.
Medical conditions that cause rapid transit of food through the intestines are also common causes. Diarrhea, regardless of its cause, can lead to green stool because bile does not have sufficient time to break down and change color. This rapid movement can be triggered by infections from bacteria like Salmonella or E. coli, viruses such as norovirus, or parasites like Giardia. Conditions like Irritable Bowel Syndrome (IBS) or Inflammatory Bowel Diseases (IBD), such as Crohn’s disease and ulcerative colitis, which involve altered gut motility, can also result in green stool. Colon cleanses or diets with very high fat content, like the ketogenic diet, can also increase bile production.
When to Seek Medical Advice
While occasional green stool is often benign, certain circumstances warrant consultation with a healthcare professional. Contact a doctor if green stool persists for more than a few days and cannot be easily attributed to dietary changes. Persistent color changes should be evaluated.
Seek medical attention if green stool is accompanied by other concerning symptoms. These include:
Severe abdominal pain or cramping
Fever
Vomiting
Signs of dehydration
Blood in the stool, appearing as bright red or black and tarry
Severe and persistent diarrhea
Feeling generally unwell
Prompt medical evaluation is advised if these symptoms occur.