What is small intestinal bacterial overgrowth (SIBO)?

Small intestinal bacterial overgrowth (SIBO) is a condition that affects the small intestine as a result of bacteria that normally grows in the gut (microbiome) becoming unbalanced and overgrows in the small intestine.

Most of the gut bacteria are supposed to be found in the large intestine (colon) where they help to ferment non-digestible substrates, produce certain vitamins and short chain fatty acids, contribute to faecal mass formation production, break down food, absorb vitamins and eliminate waste. If these 'healthy' bacteria begin to colonise the small intestine excessively, SIBO occurs. 

What are the symptoms of SIBO?

The symptoms of SIBO include:
 

• Abdominal pain after eating
• Bloating and gas
• Diarrhoea 
• Constipation
• Regularly feeling full
• Indigestion
• Rosacea and skin rashes
   

What are the causes of SIBO?

The abnormally slow movement of the digestive system is a factor for causing SIBO. As well as low levels of stomach acid, physical abnormalities of the small intestine and a weakened immune system.

People with medical conditions such as Crohn's disease, celiac disease, HIV, diabetes, IBS and fibromyalgia are also at risk of developing SIBO.

Other risk factors may include old age, being female, previous bowel surgery, overuse of antibiotics and drinking alcohol.
 

How is SIBO diagnosed?

SIBO can be frequently missed because it causes a wide range of symptoms mimic by other conditions. A gastroenterologist will ask about your symptoms and recommend a SIBO test on the basis of your clinical symptoms. 
 

A glucose or lactulose breath test is required to diagnose SIBO. This is a simple and non-invasive test. It measures the amount of hydrogen or methane in your breath following the ingestion of the mixture of the aforementioned substrates and water. A rapid rise in exhaled hydrogen or methane indicates excessive bacteria in your small bowel.  

How is SIBO treated? 

SIBO is treated with antibiotic therapy and dietary changes. It is recommended that you follow a low FODMAP diet, which limits carbohydrate intake in foods such as wheat, legumes, milk, yoghurt, fruits, honey and anything containing added sugars. 
Antibiotics can help to stabilise the gut bacteria by reducing the number of intestinal bacteria.

Any pre-existing medical conditions, such as motility disorders or unnecessary treatment with PPIs should be appropriately reviewed

Repeated treatment with antibiotics might be required only in a very specific circumstances and a review of your case by a gastroenterologist expert in the topic is recommended.