Bowel Movement Odor (Bad Smell of Stool) Causes, Remedies

Stool naturally has an unpleasant odor and this odor can vary. Usually these variations are with changes in the diet, certain lifestyle factors that may change bowel habit or with the use of medication that may reduce or increase frequency of bowel movements. In most of these cases the change in odor is temporary and not usually a cause for concern.

What causes stool odor?

Most of us do not give the odor of stool much thought. We know it smells unpleasant but understanding why it normally has this unpleasant smell is important in understanding how the odor may change. Stool is a combination of undigested material, waste substances, water, digestive secretions like enzymes and mucus, as well as bacteria and other microbes like fungi.

The passage of some of these substances takes hours and even days to reach the end portions of the large intestine. It decomposes and ferments with the action of the digestive enzymes coupled with the action of the normal intestinal flora which feeds off the residual nutrients. These chemical processes and microbial action produces gas which also contributes to the odor of stool, as well as to the odor of flatus.

While it may seem unnecessary to be concerned about the offensive odor of stools, it can actually be a symptom of certain diseases. Some of these diseases may be serious in nature and even lead to complications. There may also be other symptoms that need to be noted along with the foul odor. Diarrhea, constipation, nausea, vomiting, bloating, excessive belching, excessive flatulence, abdominal cramps or pain and changes in appetite and weight may be some of the other symptoms that occur.

Causes of Bad Bowel Movement Odor

Bowel movement odor that is foul, beyond the usual unpleasant smell, is most likely due to a change in the diet. By consuming foods that are not typical for a person’s regular diet, the odor of the stool may seem uncharacteristic. Certain foods are known to contribute towards offensive odors, like substances such as hydrogen sulfide. Diets high in sulfur foods can therefore contribute to these types of odors.

Other two important factors that may contribute to bad-smelling bowel movement includes:

  • Changes in normal intestinal flora, including an overgrowth of even the “good” bowel bacteria or the presence of “bad” bacteria.
  • Inability to digest and absorb nutrients which provides a larger food source for the normal intestinal flora (the naturally occurring bacteria.

This change in normal intestinal flora and problems with digestion/absorption is associated with a number of different gastrointestinal conditions. Identifying the exact cause may require various diagnostic investigations like an upper GI endoscopy or colonoscopy, barium x-ray, esophageal manometry and a stool test, among other tests.

Overgrowth and Infections

A number of different gastrointestinal disturbances can change the normal intestinal flora or introduce pathogens into the gut. This is mainly seen with conditions like food poisoning, infectious gastroenteritis, infectious enterocolitis and small intestine bacterial overgrowth.

  • Food poisoning is where toxins produced by bacteria, viruses or protozoa irritates, inflames and damages the intestinal lining, It may be spread through contaminated food or water.
  • Gastroenteritis is inflammation of the stomach and intestines caused by bacterial, protozoal or viral infections. It is a common gastrointestinal infection, often caused by viruses and known as the stomach flu.
  • Enterocolitis is inflammation of the small and large intestines cased by bacteria, protozoa or viruses. These infections are acquired in the same way as gastroenteritis.
  • Small intestinal bacterial overgrowth (SIBO) is where the bacterial population within the small intestine increases substantially. It is caused by anatomical abnormalities, disturbances in the protective mechanisms that prevent bacterial growth in the small intestine and with disorders in gastrointestinal motility.

Maldigestion and Malabsorption

Disturbances in digestion and absorption can occur for a number of different reasons. When the digestive enzymes are deficient or malfunctioning, normal digestion is impaired. Rapid movement through the bowels and diseases of the gastrointestinal lining can affect absorption of nutrients. This may be seen in these conditions:

  • Exocrine pancreatic insufficiency is where the digestive enzymes secreted by the pancreas is insufficient for normal digestive action. This may be seen with conditions like pancreatitis.
  • Food intolerance is where the body lacks an enzyme necessary to digest specific nutrients. The most common is lactose intolerance where a deficiency of the enzyme lactase impedes the the breakdown of lactose, a milk sugar.
  • Irritable bowel syndrome (IBS) is where the normal gastrointestinal motility is either too rapid or too slow and spasms of the bowel wall muscle may occur.
  • Inflammatory bowel disease (IBD) is an autoimmune condition where parts of the gastrointestinal tract, particularly the bowels, is inflamed.
  • Short bowel syndrome is a condition where a portion of the small intestine has been surgically removed or is absent thereby reducing the absorptive surface of the gut.
  • Celiac disease is inflammation of the bowels caused by contact with gluten due to a sensitivity to this protein. This is not an intolerance but rather an immune sensitivity to gluten.

Other Conditions

  • Bowel obstruction
  • Cystic fibrosis
  • Gallbladder disease

Remedies for Bad Stool Odor

When bad stool odor is due to medical conditions such as infections and other gastrointestinal diseases then it requires medical treatment. Conservative measures like dietary and lifestyle changes may be helpful in managing these conditions but medication and/or surgery may be necessary.

  • Keep a food diary to track and monitors possible trigger foods that may be contributing to the foul-smelling stools. It is usually accompanied by foul-smelling flatus.
  • Avoid foods that are known to contribute to unusually foul-smelling flatus as these foods may also play a role in offensive-smelling stools.
  • Eat smaller meals more frequently to ensure effective digestion and maximum absorption thereby reducing residual nutrients for the bowel bacteria and fungi.
  • Ensure sufficient fiber in the diet to regulate bowel habit as food and waste that remain in the bowels for too long (like during constipation) may decompose and ferment further.
  • Drink sufficient quantities of water. For many of the same reasons as a high-fiber diet, it will improve bowel habit and prevent hard stools.

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