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Dark Green Stool

Dark green stool is normally the result of having infant formulas, iron supplements, or the intake colors and dyes through food. However, if accompanied with other health issues, it may be an indication of an infection or gastrointestinal problems.
Ningthoujam Sandhyarani
Last Updated: Apr 23, 2018
A stool analysis for color and texture variations as well as microbial content, is important for the detection and/or confirmation of several diseases. However, in most cases, such variations are simply due to dietary changes, and may not be a cause for concern.
The bowel movement of a healthy individual is usually yellowish-brown in color. It comprises undigested food particles, intestinal bacteria, waste material, and water. However, occasional instances of spotting dark brown, green, black, or reddish-colored feces is also normal.
Although green stool (light or dark) is generally the result of certain dietary factors, and is considered normal, it may also signify digestive or intestinal problems, particularly if the sighting frequency is high. Hence, it is advisable to identify the causes for the persistence of this condition.
Dark green poop is most often observed in babies and toddlers, especially newborns and formula-fed infants. In fact, the first stool matter of a neonate is dark green or blackish-green in color, and is known as meconium. It contains material ingested in utero, namely amniotic fluid, fetal hair (lanugo), bile, intestinal epithelial cells, and water. Such dark green stool is passed for the first few days of a baby's life, after which yellow-colored poop is observed owing to the digestion of breast milk.
In children and adults, the occasional instances of dark green stool are mainly due to the excessive consumption of dark green vegetables and food colors, iron supplements, certain medications, as well as infections and digestive system disorders. The different factors that may lead to dark green poop in infants, children, and adults have been described below:
Infant formulas containing iron often lead to dark green coloration of stool. High intake of iron-rich vegetables, and dietary supplements containing iron salts may lead to dark green stool in toddlers, children, and adults. The green color has been attributed to the presence of excess iron salts excreted by the body through fecal matter.
Food color
Chemicals that serve as edible food color may not be metabolized through the normal digestive and metabolic processes, and may be excreted out through the feces. Hence, the intake of food items like Jell-O, candy, packaged beverages, ice pops, popsicles, etc., may lead to green colored stools.
Bile pigments
The breakdown of bile takes place during the digestion process that occurs in the large intestine. During diarrhea, a quick passage of chyme through the large intestine results in the presence of green-colored bile pigments, leading to dark green, watery stool. It may be the result of:

» Bacterial infections like Vibrio cholerae, Enterotoxigenic Escherichia coli, Shigella spp., Salmonella spp., etc.

» Gastroenteritis due to protozoan parasites like Giardia lamblia or viruses like rotavirus, adenovirus, calicivirus, etc.

» Crohn's disease and ulcerative colitis that are characterized by an inflammation of the gastrointestinal tract.

» Pseudomembranous colitis which is the result of excessive use of antibiotics followed by overgrowth of colonic bacteria called Clostridium difficile.

» Celiac disease or gluten intolerance characterized by a damaged intestinal lining owing to an immune reaction against gluten.

» Food poisoning (botulism) due to the intake of food contaminated with C. botulinum.

Other Causes
  • » Consumption of ample amounts of green vegetables like spinach, peas, broccoli, lettuce, etc.
  • » Intestinal malabsorption
  • » Excessive use of laxatives
  • » Antibiotics and other medicines
Possible Health Risks

Dark green feces is not a medical concern as long as it is temporary; the stool structure is normal; and there are no problematic symptoms. If the stool color is related to ingested food items, iron supplements and/or therapeutic medications, one's normal condition will be restored when the intake is discontinued.
However, the presence of mucus or blood in the stool and/or symptoms like recurrent abdominal pain, nausea, vomiting, fever and chills, rectal pain, indigestion, fatigue, etc., demands professional consultation. Fever and chills may indicate a viral infection, whereas abdominal pain and other gastrointestinal symptoms may be due to digestive system disorders or food poisoning.
Diagnosis and Treatment
In case of recurrent episodes or the persistence of dark green stool, a stool analysis for other physical properties, and microbial investigations are advised. In addition, blood tests, a barium X-ray, colonoscopy and other diagnostic investigations may be required depending on the precise set of symptoms and their severity.
The treatment prescribed depends on the etiology, and mostly includes dietary modifications. In case of persistent green stool, individuals may experience dehydration due to fluid loss, and hence may be advised to drink water frequently. Infectious diarrhea may be treated using appropriate antibacterial and antiviral medication. Anti-inflammatory drugs and analgesics may be prescribed to alleviate inflammation (if any), and the pain associated.
This HealthHearty article is for informative purposes only, and should not be used as a replacement for professional medical advice.