by Nicole Evans M.D.

Created on: August 03, 2010   Last Updated: December 22, 2011

In normal, healthy individuals the intestines are colonized by beneficial bacteria soon after birth.  The numbers of bacteria in the bowels are kept in check via several different mechanisms.  However, in some individuals these mechanisms are altered and the ensuing environment within the intestines can promote the excessive growth of intestinal bacteria.  This condition is known as small intestinal bacterial overgrowth (SIBO).

Symptoms of bacterial overgrowth syndrome:

Individuals with bacterial overgrowth of the small bowel may be free of symptoms or may have a variety of gastrointestinal complaints such as:
-bloating
-abdominal discomfort
-watery diarrhea
-dyspepsia (upset stomach)
-weight loss

Additionally, people with small bowel bacterial overgrowth may suffer from malnutrition.  Normally, intestinal bacteria assist in the breakdown of certain dietary sugars and the production of vitamins such as folate and vitamin K.  However, with bacterial overgrowth the abnormally high numbers and/or alteration in the types of bacteria in the intestines actually cause malabsorption of essential nutrients.  

Causes of intestinal bacterial overgrowth:

Excessive growth of bacteria in the intestines is normally prevented by several defense mechanisms including:
-Peristalsis (forward churning motion of the stomach and intestines)
-Strong acid conditions within the stomach
-Enzymes that break down proteins in the small intestine
-Mucus lining the inner layer of the intestine
-Normal immune system function

The most common medical conditions that predispose an individual toward bacterial overgrowth include chronic pancreatitis and syndromes that cause poor intestinal motility.  Individuals with short bowel syndrome, intestinal fistulas, liver disease, and immunodeficiency may also be more prone to small intestine bacterial overgrowth.  In addition, there appears to be an association between bacterial overgrowth and irritable bowel syndrome in some individuals.  People with IBS and bacterial overgrowth generally benefit from simultaneous treatment with antibiotics and probiotics.  

Treatment of small bowel bacterial overgrowth:

In general, the treatment of small bowel bacterial overgrowth requires treatment of the underlying disease, adjusting the diet, administering antibiotics to reduce the bacterial load within the gut, and calming the inflammation created within the intestinal wall.

The optimal diet for individuals with excessive intestinal bacteria is a low carbohydrate, low fiber, high fat diet.  This is because carbohydrates are the primary nutritional source for bacteria.  In contrast, fat is not metabolized well by bacteria and so provides a good source of calories for people with bacterial overgrowth.  The high fat diet should be composed of healthy fats such as those that come from fish, avocados, nuts, flax, etc.

Often, individuals with bacterial overgrowth will experience symptom improvement with the discontinuation of lactose.  Lactose is a sugar found in most dairy products.  The break down of lactose requires an enzyme called lactase that is often deficient in adults with small intestinal bacterial overgrowth.

If you suspect you are experiencing the signs and symptoms of small bowel bacterial overgrowth (SBBO) syndrome contact your doctor to confirm the diagnosis and begin appropriate treatment.

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