What is SIBO?
Normally, bacteria are found in the trillions in the large intestine, where they perform various functions for the human body. SIBO is defined as an increase in the number of bacteria, and/or changes in the types of bacteria present in the small intestine. In most patients, SIBO is not caused by a single type of bacteria, but an overgrowth of the bacteria that should normally be found in the colon.
Prevalence estimates are based on a percentage of the population with Irritable Bowel Syndrome (IBS). This is 11-14% of the population globally and 17% in New Zealand. It is the most common gastrointestinal diagnosis in primary care although it is thought that up to 50% of people with symptoms of IBS do not consult their GP. Studies also show that over 50% of patients diagnosed with IBS actually have SIBO.
Common symptoms of SIBO
- Postprandial bloating/abdominal distension with associated discomfort
- Gas and belching
- Food Intolerances
- Constipation (generally associated with methanogenic bacteria)
- Diarrhoea (generally associated with hydrogenic bacteria)
- Immune activation (e.g. food sensitivities)
- Nutrient deficiencies i.e. vitamin B12 & Iron
- Weight loss / weight gain
- Fatigue or brain fog
SIBO has been shown to negatively affect both the structure and function of the small bowel. It may significantly interfere with digestion of food and absorption of nutrients, primarily by damaging the cells lining the small bowel (the mucosa).
Bacterial endotoxins and Lipopolysaccarides (LPS) can have wide ranging effects systemically. Additionally, this damage to the small bowel mucosa can lead to impaired gut permeability which is known to have a number of potential complications including immune reactions that cause food allergies or sensitivities, generalized inflammation, and autoimmune diseases.
There are two main types of bacteria present in SIBO:
- Methanogenic bacteria – associated with constipation and biliary dyskinesia
- Hydrogenic bacteria – often associated with loose stool