We all have bacteria in our intestines. However, we have much more bacteria in our colon, or large intestine, than we have in our small intestine. If the small intestine develops a similar amount and type of bacteria as the colon, this can lead to several potentially serious problems.
When this happens, it is called Small Intestinal Bacterial Overgrowth (SIBO). Some people refer to it as Small Bowel Bacterial Overgrowth Syndrome (SBBOS). These two terms refer to the same condition.
Many of the symptoms of SIBO manifest very similarly to the symptoms of celiac disease, so if your symptoms aren’t improving on a gluten-free diet, your doctor may want to assess you for SIBO.
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What Is SIBO?
The entire digestive tract is a long tube of muscles, which process food and push it along. A careful balance of enzymes, gastric acids and churning helps digest your food and keep it moving through your digestive tract.
If any of these systems become compromised, food or bacteria may linger, ferment, and propagate within the small intestine instead of being killed or swept into the large intestine where it is eventually eliminated from the body.
In addition, conditions or surgical procedures may result in pouches along the wall of the small intestine. When chyme or fecal matter gets stuck in these pouches, bacteria flourish around them.
Symptoms can result from the bacteria consuming nutrients before your small intestine can absorb them, or they may result from the by-product of the bacteria’s digestive process. In some cases the combination of the bacteria eating your nutrients and producing its own by-products can set off a chain of events. These are the most common symptoms associated with SIBO:
- Abdominal pain and cramping
- Fatty stool
- Weight loss
If symptoms persist and SIBO isn’t properly treated, more severe complications can develop, including liver disease and osteoporosis.
Celiac disease may trigger small intestinal bacterial overgrowth in a number of ways. The inflammation of the small intestine caused by celiac disease results in reduced nutrient absorption. This inflammation may also negatively affect intestinal motility, which means food isn’t properly pushed along your digestive tract to your colon. Last but not least, celiac disease may result in reduce pancreatic enzymes, which means nutrients aren’t properly broken down for absorption. Each of these consequences of celiac disease help feed bacteria and allow it to flourish in the small intestine.
One study published in the April 2003 issue of the American Journal of Gastroenterology suggested that SIBO is most common in non-responsive celiac disease patients. This is probably because in those patients, bacteria has had a longer time to survive and thrive within the patient’s damaged small intestine.
But celiac disease is not the most common cause of SIBO, and in fact, there are times when a patient or doctor may initially suspect celiac disease when in fact the underlying condition is bacterial overgrowth in the small intestine.
Sometimes it may be difficult to determine whether a condition led to the development of SIBO or the treatment of that condition led to it. For example, small bowel diverticulosis may cause SIBO directly. Diverticulosis occurs when you develop pouches in the wall of your intestine. If those pouches become inflamed or infected, it becomes diverticulitis. Sometimes diverticulitis is treated with antibiotics. Those antibiotics may throw the small intestine’s bacteria population out of balance, killing good bacteria and allowing bad bacteria to flourish.
In general, SIBO develops when some condition or medication creates one of two different situations. First, it may negatively affect motility, preventing your digestive tract from sweeping bacteria and fecal matter through your digestive tract to your colon and rectum.
Secondly, a condition or medication may reduce gastric acid or digestive enzymes. Gastric acids help kill bad bacteria and digestive enzymes help your body absorb nutrients so the bad bacteria can’t feast on it. When you’re low on these critical digestion chemicals, your small intestine may struggle to keep the bacteria population down.
These are the most common causes of Small Intestinal Bacterial Overgrowth:
- Anatomical abnormalities
- Antibiotics, especially chronic use of antibiotics.
- Gastrointestinal obstructions
- Immunosuppressant medications (sometimes prescribed for refractory celiac disease)
- Low stomach acid (even if caused by a medication, such as proton pump inhibitors)
- Narcotics and benzodiazepines (known to reduce motility)
- Pancreatic Insufficiency, or reduced digestive enzyme production
- Small bowel diverticulosis
- Surgical procedures involving the small intestine
- Type 1 Diabetes
Diagnosis can be tricky because SIBO is often mistaken for other conditions, or it may be the result of other conditions.
The gold standard for diagnosis is a biopsy of the jejunum, the middle third of your small intestine. With this biopsy, doctors measure the population density and profile of the bacteria in your small intestine.
Prior to a biopsy, doctors may begin isolating SIBO from other conditions using blood tests to assess for reduced vitamins and minerals in your blood, an X-ray of the small intestine to identify obstructions, and a fecal fat test to test for poor absorption of lipids and fat-soluble vitamins.
In many cases, the first act of treatment is to treat the underlying condition causing the bacterial overgrowth. In some cases, that may mean substituting or stopping certain medications. Sometimes additional treatment may be required even after the causing condition has been treated or eliminated.
Where motility appears to be the main culprit, your doctor may prescribe motility-increasing medications. In cases where obstructions or other types of damage to the small intestine is the source of the problem, surgery may be required.
In the short term, making sure the patient obtains sufficient nutrients and fluids is critical. In more severe cases, this may require intravenous (IV) fluids.
A FODMAPs diet may help curb the population of bad bacteria. The FODMAPs diet involves removing specific carbohydrates known to be poorly digested in the upper small intestine. These poorly digested carbohydrates then tend to ferment in the lower small intestine.
For more on FODMAPs, visit the following resources:
The FODMAPs diet is more for Irritable Bowel Syndrome than for SIBO, but in milder cases of SIBO it may help. You might also want to look into why I frown on fructose.
Small intestinal bacterial overgrowth is a little like celiac disease in that if you suspect it is the cause of your symptoms, you may have to lead your doctor to consider diagnosis. It is often either masked by other conditions or caused by other conditions. It isn’t one of the first things most doctors will consider or think about when assessing your symptoms.