Causes of a Green Bowel Movement

Food

Green bowel movement may be normal for a person that ingests a lot of:

  • Green leafy vegetables like broccoli, lettuce, spinach, cabbage
  • Black licorice
  • Baby formula – vegetable mashes
  • Artificial colors, commonly added to ice creams, soda, fruit juices, or other drinks, morning cereals, milk products, sweets, etc.
  • Iron-rich foods like enriched breakfast cereals, red meat, spinach, beans, etc.

Dark green color may persist for up to five days after ingesting above mentioned foods. Supplements or artificial colors may give bright green color to the stool.

In infants, stool is green in first days after delivery, and later due to breastfeeding. Some baby formulas can also give green color to infant stool.

Children on clear-liquid “starvation diet” during illness may have green watery stools.

Medications and Supplements

Medications and supplements, giving stool green color, if taken by mouth:

  • Iron supplements
  • Laxatives – due to shortened bowel transit time
  • Algae
  • Chlorophyll
  • Children syrups often contain sweeteners fructose or sorbitol that both can speed up peristalsis what may result in green bowel movement
  • Vitamins /mineral supplements, or eventually any other medication or supplement taken by mouth, if it is artificially colored, or if it contains fructose or sorbitol, that may speed up peristalsis

Causes of Green Diarrhea

Decreased Bowel Transit Time

Green bile, after excretion from the liver into duodenum, slowly changes to yellow, and then to brown color due to chemical changes performed by normal intestinal bacteria and enzymes. When the bowel content flows through the intestine fast, original bile color does not change, resulting in green or yellow stool. Causes of decreased bowel transit time include:

  • Diarrhea – loose bowel movements; there are several causes of loose bowel movements, including food poisoning (giardia and salmonella infection often result in green diarrhea), rotavirus infection, food allergies, lactose intolerance, fructose malabsorption, celiac disease, Crohn’s disease, ulcerative colitis, and so on.
  • GERD (Gastro-Esophageal Reflux Disease
  • Thyrotoxicosis - elevated levels of hormone thyroxine in the blood, usually due to autoimmune thyroid disorder (Grave’s disease)
  • Impaired gut innervation, common in diabetes

Impaired Bile Re-absorption in the Small Intestine

Bile salts are absorbed into blood mainly from last part of small intestine (terminal ileum). Causes of impaired bile re-absorption are:

  • Inflammation of the small intestine, mainly due to Crohn’s disease
  • Surgical removal of the terminal ileum

What to Do, If You Have Green Bowel Movements?

Green bowel movements due to ingested food or medication/supplement are normal, and do not require any action. In all other cases, especially if symptoms like fever, diarrhea, constipation, weight loss, or general malaise are present, you should visit a doctor, because a serious underlying disorder may be present.

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Article reviewed by Dr. Greg. Last updated on March 3, 2010