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An unusual color of the bowel movement could be caused by a food or dietary supplement but it could also be a symptom of a serious problem. The stool color varies from person to person but it also may vary from stool to stool in the same person.

4007890542_9de3870e22.jpgStool color is generally influenced by what you eat as well as by the amount of bile (a yellow-green fluid that helps digest fats) in the stool. As bile pigments travel through your gastrointestinal tract, they are chemically altered by enzymes changing the pigments from green to brown. The changes in the stool color don’t have to indicate some disorder. Consuming black licorice, lead, iron pills, bismuth medicines, or blueberries can also cause black stools. Beets and tomatoes can sometimes make stools appear reddish.

Bloody or Tarry Stool

Bloody stools often indicate an injury or disorder in the digestive tract. There is a big difference between the stool filled with fresh blood and is the stool that is black due to blood in it. Melena is a term used to describe black, tarry, and foul-smelling stools while hematochezia refers to red or maroon-colored stools. Blood in the stool can originate from anywhere along the digestive tract from the mouth to the anus.

A black stool usually means that the blood is coming from the upper part of the gastrointestinal tract. This includes the esophagus, stomach, or the first part of the small intestine. The reason that blood appears like tar is that it has been exposed to the body's digestive juices.

Common causes of upper GI bleeding are:

  • Bleeding stomach or duodenal ulcer
  • Gastritis
  • Esophageal varices
  • A tear in the esophagus from violent vomiting
  • Trauma or foreign body
  • A lack of proper blood flow to the intestines-ischemia
  • Vascular malformation

Maroon-colored stools or fresh red blood in the stool usually suggests that the blood is coming from the lower part of the GI tract, which includes large bowel or rectum.

Hemorrhoids and diverticulitis are the most common causes of lower gastro-intestinal bleeding.

Other common causes of lower GI bleeding are:

  • Anal fissures
  • Intestinal infection
  • Vascular malformation
  • Inflammatory bowel disease
  • Tumor
  • Colon polyps or colon cancer
  • Trauma or foreign body
  • Ischemia

Rectal bleeding can also be caused by a variety of things:

  • Constipation
  • Hemorrhoids
  • Diverticular bleeding
  • Infection
  • Colon polyps
  • Peptic ulcers
  • Inflammatory bowel disease
  • Lack of blood supply to the bowel
  • Colorectal cancer


Fecal occult blood test

Sometimes the blood may be present in such small amounts that you cannot actually see it. However, it is detectable by a chemical test of the stool called fecal occult blood test.

Endoscopy and x-rays

If there is enough blood to change the appearance of your stools, the doctor will want to know the exact color in order to estimate the site of bleeding. Sometimes the endoscopy or special x-ray studies are needed. In these cases, your doctor can test the stool with a chemical to rule out the presence of blood.

Other tests:

  • Blood studies, including a CBC and blood differential
  • Colonoscopy
  • Gastroscopy  
  • Angiography
  • Barium studies
  • Stool culture
  • Tests for the presence of Helicobacter pylori infection

Prevention of GI-bleeding

  • You should eat vegetables and foods rich in natural fiber and low in saturated fat because these foods may prevent constipation, hemorrhoids, diverticulosis, and colon cancer.
  • A prolonged or excessive use of anti-inflammatory drugs like ibuprofen, naproxen, and aspirin should be avoided because they can irritate the stomach and cause ulcers.
  • Large amounts of alcohol can irritate the lining of the esophagus and stomach.
  • Smoking is linked to peptic ulcers and cancers of the GI tract.
  • Stress is also a possible factor in peptic ulcer disease. 

Diarrhea or watery stool

After a meal, the small intestine absorbs fluid and nutrients from the food that have been eaten. Anything that disrupts this process may cause diarrhea. For example:

Viral infection
Viruses are the most common cause of diarrhea. It is proven that an invading virus can damage the lining of the small intestine, disrupting fluid and nutrient absorption. Fortunately, the symptoms usually disappear in approximately three to four days.

Bacterial infection
Some bacteria which can contamine food or water can release a toxin that causes intestinal cells to secrete salt and water into the lumen of the bowel. This is more then the capacity of small intestine and colon can handle.
Other inflammatory agents
Diarrhea can sometimes be caused by a parasite or a reaction to medication, such as antibiotics. Once the parasite is eliminated or an offending antibiotic is discontinued, the diarrhea usually disappears. Caffeine and alcohol stimulate the passage of stool so consuming too much of those may cause the waste to move through small intestine and colon too quickly.

Intestinal disorder
Diarrhea may often be related to an intestinal disorder. Possible causes include irritable bowel syndrome, inflammatory bowel disease, lactose intolerance or celiac disease.

Tips for preventing diarrhea

  • Drink plenty of fluids
  • Gradually add solid foods to your diet
  • Avoid anything that may prolong diarrhea and avoid fatty foods, spicy foods and beverages containing caffeine or alcohol.
  • Don't take antacids containing magnesium

Pale or Clay Colored Stools

Jaundiced or yellow skin often accompanies clay colored stools. Since it is the bile salts excreted by the liver that give the stool a normal brown color, an obstruction to bile flow out of the liver or liver infections like viral hepatitis may produce clay colored stools. Certain medications, such as large doses of Kaopectate and other anti-diarrhea drugs may also cause such symptoms.

Mucus in stool

Mucus in stool is generally not an indication of a serious problem as stool normally contains a small amount of mucus. It is a jelly-like substance that intestines make to keep the lining of colon moist and lubricated. Increased amounts of mucus in stool may occur with diarrhea or constipation.
However, sometimes it can indicate an underlying medical condition such as ulcerative colitis or Crohn's disease.

Stringy stool

Although it could be a sign of normal eating patterns, it may also be a cause for concern. The patient could have a parasitic infection.

Smelly or Greasy stool

Changes in your diet may cause changes in the smell, texture and color of your stool. Some say a vegetarian diet causes less odor in the stool, while fat seems to cause smellier stools. If someone has particularly greasy, smelly, floating stools, he or she may have a problem absorbing fat from the gut. The problem may be the pancreas or small bowel.

Silvery white, gray or pale yellow stools

In such cases. a physician should be consulted immediately as disorders involving your liver, gall bladder or pancreas may be the cause to this, and may represent a serious disease.


Constipation is a condition characterized by repeated painful or difficult passage of hard stool or having a bowel movement only once or twice a week. Eventually, the waste becomes dry and difficult to pass. There are a few common culprits:

  • Age
  • Eating and drinking habits
  • Sedentary lifestyle
  • Medication
  • Inattention to bowel habits
  • Other medical problems such as hypothyroidism and Parkinson's disease.

Self-care for constipation

Lifestyle changes are often the safest way to manage constipation. To help ease symptoms:

  • Drink plenty of fluid
  • Eat more fiber
  • Regular meals could be beneficial in treating constipation
  • Exercise stimulates the intestinal muscles
  • Reduce stress because stress can slow digestion.

Review of conditions that can affect color of the stool:

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