The causes of SIBO or Small Intestinal Bacterial Overgrowth and how it develops is not entirely clear, and it’s still somewhat debatable. SIBO begin when there is a disruption in the mechanisms that control the number of bacteria that live in the small intestine. There are at least seven risk factors that are potential causes for that disruption.
- Structural or anatomic issues, for example, after surgery, if there was damage to nerves that enervate the small intestine, or patients with Cystic Fibrosis
- Motility disorders, so dysfunction of the migrating motor complex
- Irritable bowel syndrome
- Metabolic diseases like diabetes
- Low stomach acid
- Organ system dysfunction
The 3 Primary Causes of SIBO
According to Chris Kresser, Functional Medicine and SIBO expert, three primary processes cause SIBO:
- Low gastric acid secretion
- Small intestine dysmotility
- Disrupted microbiota
Low gastric acid secretion
Stomach acid suppresses the growth of ingested bacteria, which would limit bacteria in the upper small intestine. For this reason, hypochlorhydria, or low stomach acid, is a primary risk factor for SIBO.
Low stomach acid can develop:
- When H. pylori bacteria are present
- With chronic stress
- As a consequence of ageing
If a person has heartburn and they take these acid-suppressing drugs for a significant period, it reduces stomach acid it may predispose them to develop SIBO.
Small intestine dysmotility
The next primary of the causes of SIBO is impaired intestinal motility or dysfunction of the migrating motor complex (MMC). The MMC sweeps residual debris through the gastrointestinal tract so abnormalities in the MMC may predispose to the development of SIBO.
The third of the primary causes of SIBO is a disrupted gut microbiome, but there is less research on this proving a direct cause. There are however several lines of evidence that support an association.
One is that it’s well-established that antibiotic use can lead to disrupted gut microbiome and in turn SIBO.
Celiac disease also leads to a disrupted gut microbiome, and there’s a definite connection between celiac and SIBO.
Disrupted gut microbiome has been shown to cause dysfunction of the ileocecal valve, and we know that dysfunction of the ileocecal valve can lead to translocation of bacteria that should stay in the large intestine into the small intestine, which is one of the principal ways that SIBO develops.
This article is not intended to provide medical advice, diagnosis or treatment.
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