Small intestinal bacterial overgrowth (SIBO) is an under-diagnosed common digestive problem that likely affects 15% of the general population and 80% of those who have irritable bowel syndrome (IBS). The symptoms of SIBO include abdominal pain or discomfort, bloating, diarrhea, constipation and gas or bloating. SIBO results from an increase in the number or change in composition of the bacteria that inhabit the small intestine.
This bacterial overgrowth most commonly comes from bacteria that normally live in the large bowel where there are 1 billion bugs per milliliter of fluid. By contrast, the small intestine normally has fewer species and numbers, in the range of 10,000 microbes per milliliter. Low stomach acid, IBS, celiac and non-celiac gluten sensitivity, bowel surgery, alcohol consumption, diabetes and multiple course of antibiotics are a few of the risk factors associated with SIBO.
While the underlying causes of SIBO are complex it almost always involves movement of large bowel bugs moving into the small bowel. The small bowel travels from the stomach for about 20 feet to the large bowel where the two are separated by the ileocecal valve which ideally helps to keep the large bowel bugs from entering the small bowel. Inadequate ileocecal valve closure due to the risk factors listed above is often a contributing cause of SIBO.
Rifaximin is an antibiotic that is commonly used to treat SIBO however almost half of those treated with antibiotics have a recurrence within a year. Some studies on botanical antimicrobials show slightly better outcomes with herbal therapies being better than prescriptive however just shy of half of people with SIBO need two treatments regardless of whether antibiotics or botanicals are used. These results highlight the fact that treating bacterial overgrowth is often not enough and that the other underlying causes must also be addressed (which I’ll write about next week).