Individuals with immune deficiencies, such as with HIV, are also prone to bacterial overgrowth.

This valve prevents the “backflow” of colonic contents from re-entering the small intestine, but individuals with a dysfunctional ileocaecal valve are at increased risk of developing SIBO as colonic bacteria can enter and colonise the small intestine more easily 4. Poor function of the the ileocaecal valve, located at the junction between the ileum (small intestine) and the caecum (start of the large intestine), is also a risk factor for SIBO. For more about antibiotics and the microbiome, take a look at this article in the Probiotics Learning Lab: Probiotics and Antibiotics. Antibiotics can alter the composition of bacteria in the small intestine leading to increased growth of pathogenic bacteria. Recurrent or long-term antibiotic use is also a risk factor for the development of SIBO. Structural abnormalities in the small intestine such as post gastric surgery.Systemic diseases such as Diabetes Mellitus, systemic sclerosis, liver disease.Medication – long term acid suppressant use including Proton Pump Inhibitors (PPIs)Ĭauses of reduced small intestinal motility:.Normal intestinal motility keeps the contents of our small intestine moving and prevents stasis of food and bacteria, which can lead to bacterial overgrowth. Stomach acid inhibits the growth of bacteria that is ingested in our food. The two most common causes of SIBO are reduced gastric acid secretion and impaired small intestinal motility 3. This can damage the lining of the intestinal tract, flattening villi and thinning the mucosa which can in turn, prevent optimal absorption of nutrients, in some cases leading to vitamin and mineral deficiencies.

Long term, bacterial overgrowth can lead to local intestinal mucosal inflammation. In the short term, increased gas production can lead to bloating, flatulence, nausea and abdominal pain. This results in increased gas production, usually hydrogen and sometimes methane gases. When there is an abnormally high quantity of bacteria in the small intestine, there is increased bacterial fermentation of food as it enters from the stomach. The small intestine usually is colonised by some bacteria but much less than the large intestine. Small Intestinal Bacterial Overgrowth or SIBO is the excessive growth of bacteria in the small intestine.

Small bowel intestinal overgrowth