Common Digestive Conditions

Small Intestinal Bacterial Overgrowth (SIBO)

The small bowel / intestine usually has very low levels of bacteria at the top end (the duodenum), and then more bacteria begin to proliferate as we move towards the end of the small bowel. Small bowel bacteria measure in the billions, as opposed to the trillions we find in the large bowel. It is not normal for us to have large numbers of bacteria growing in our small bowel, and when we do, this is called Small Intestinal Bacterial Overgrowth, or SIBO.


What causes SIBO?

A number of factors can contribute to development of SIBO but sometimes there is no obvious cause. Factors include: motility problems such as those that occur in some people with neurological conditions, diabetes or indeed IBS. Previous bowel surgeries can also be a cause.


Why and what problems do bacteria in the small bowel cause?  

Food is broken down in the small intestine into small particles like sugars, simple fat molecules and the building blocks of proteins called amino acids. When there are bacteria present, they interfere with the absorption of these substances and digest (ferment) the sugars and amino acids themselves. The result of this bacterial fermentation is the production of gas and other by-products, which can lead to bloating, flatulence and diarrhoea.


How is SIBO diagnosed? 

The Hydrogen and Methane breath test is the most common test used in everyday clinical practice to detect SIBO. This is a simple and non-invasive investigation but it is not perfect and is only 60-70% accurate – both false negative and false positive results occur.


Treatment of SIBO    

The aim of all treatments for SIBO is to reduce bacterial levels in the small intestine and to relieve the symptoms. Antibiotics are currently the mainstay of treatment and the types prescribed are based on your breath test results. Treatment usually requires specialist advice.


Dietary approaches such as low sugar, low carbohydrate or low FODMAP diets have all been investigated, but the results are inconclusive. Some herbal remedies have also been shown to be as effective as antibiotics in some studies. The role of probiotics in treatment of SIBO has also been investigated, but results have been inconclusive.