Abstract
SIBO is a type of dysbiosis. It stands for small intestine bacterial overgrowth (sometimes also called BOSI—letters scrambled, same acronym—or SBBOS [small bowel bacterial overgrowth syndrome]). It is estimated that 50%–75% of patients with irritable bowel syndrome [IBS] have SIBO (diagnosed by a hydrogen breath test) and benefit from treatments to reduce SIBO. 1 Unlike the large intestine, which is teaming with microorganisms, the small bowel often has <104 organisms per mL. 2 SIBO is caused by an overpopulation of bacteria in the small intestine that normally do not form part of its balanced ecosystem. SIBO can also result from an overpredominance of generally friendly bacteria, which leads to increased fermentation of the sugars in the carbohydrates we eat. 3
The symptoms of SIBO overlap with many other disorders, but the most salient of them is an inability to tolerate the simple carbohydrates in starches, sweets, sugars, and fibers, or even supplementation with a probiotic, without developing uncomfortable symptoms of: • Gas • Bloating • Distended abdomen within 15 minutes and up to 3 hours after a meal
but may also include: • Flatulence • Nausea • Vomiting • Diarrhea (including steatorrhea or greasy, loose stools because of fat malabsorption) • Fatigue • Signs of malnutrition and malabsorption (including weight loss and vitamin or mineral deficiencies) • Weight gain (paradoxically) from fluid retention and inflammation.
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If any of these symptoms are present or if the patient has recently taken or currently takes an acid reducer, such as a proton pump inhibitor (such as Nexium,® AcipHex,® Protonix,® or Prilosec®) or H2 blocker medication (such as Pepcid® or Zantac®), and experiences any of these symptoms, testing for SIBO should be done.
Malnutrition because of SIBO results from overpopulated bacteria consuming nutrients before they can be absorbed. These bacteria also inflame the small bowel, which reduces the absorption of nutrients. In conjunction with having abdominal symptoms, the patient may also feel weak and fatigued.
Notice there is some overlap between the symptoms of SIBO and symptoms of yeast overgrowth. The self-test for yeast overgrowth will help to distinguish better if the symptoms are more likely yeast-related.
Diagnosing SIBO
There is no perfect test for diagnosing SIBO, and often my colleagues treat presumptive SIBO based on symptoms, but not on objective data. The best times to test are when symptoms are vague, the person does not respond to conventional therapy, or, as in cases of presumed SIBO, the symptoms mimic other root causes, such as yeast overgrowth.
How to Test for SIBO
(1) Small bowel aspiration—The “gold standard” for diagnosing bacterial overgrowth in the small bowel is an aspirate from the jejunum or middle portion.
(2) Hydrogen and/or methane breath test—This is the best noninvasive test to diagnose small-intestine bacterial overgrowth. The test is based on the fact that there are no other sources of hydrogen or methane production in humans. After a 12-hour overnight fast, a baseline breath sample is taken, then, at various time intervals after a sugary drink, breath samples are taken.
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