What is SIBO?

SIBO occurs when bacteria migrate from their usual home in the large intestine back up into the small intestine.  There is also evidence that some bacteria may relocate from the mouth down into the small intestine.

This results in a condition known as small intestinal bacterial overgrowth (SIBO, pronounced see-bow). There are a small number of bacteria that normally live in the small intestine, but SIBO involves a larger than normal presence of bacteria in the small intestine.  

Why is SIBO a problem?

The displaced bacteria start to ferment poorly absorbed sugars and this can contribute to bloating, gas, abdominal discomfort and diarrhoea. Their presence may also result in nutritional deficiencies as they compete for nutrients such as iron and vitamin B12.

What causes SIBO?

The factors that may lead to SIBO include advanced age, slowed movement of food through the digestive tract, abdominal surgery, low stomach acid production and medications that reduce stomach acid. SIBO can accompany some existing medical conditions such as some autoimmune diseases, type 1 and type 2 diabetes or Parkinson’s disease.

How do you know if you have SIBO?

SIBO has proven difficult to diagnose. The best test involves taking a small sample of fluid from the small intestine and sending it for analysis to determine how many bacteria and the type of bacteria, are in the small intestine. However, this test is invasive and carries some risks so is not often performed.

Breath testing is more commonly done. Breath testing involves drinking a sugary liquid, usually either lactulose or glucose. The bacteria in the small intestine will ferment the sugar. This creates gases, either hydrogen or methane gas, which is absorbed across the digestive lining into the blood. The blood delivers the gas to the lungs where it is expelled in the breath. The amount in the breath is measured at specific intervals after the drink is given.

However, breath testing too has limitations and is not always a reliable indicator of the presence or absence of SIBO.  

With these limitations in testing, definitively diagnosing SIBO remains difficult. A suspected diagnosis is therefore often made on history, symptoms and response to treatment.

Treatment options

Current treatment options include antibiotic treatment, (herbal or conventional) and dietary approaches that consider frequency of meals and types of foods eaten. The low FODMAP diet and drinking an elemental formula (pre-digested nutrients) over two weeks are both nutritional approaches that are showing promise.

SIBO is an area that is receiving a lot of research interest so diagnosis and treatment options are likely to improve and become more individually targeted in the near future.


If you suspect you may have SIBO, speak with your primary health care provider to discuss the best options for you. 

Jill Burns