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 and colon where they help to break down food, absorb vitamins and eliminate waste. If these 'healthy' bacteria begin to colonise in the small intestine, SIBO occurs. 

This can lead to symptoms such as bloating, flatulence and abdominal pain.

What are the symptoms of SIBO?

The symptoms of SIBO include:

  • Abdominal pain after eating
  • Bloating and gas
  • Diarrhoea 
  • Constipation
  • Regularly feeling full
  • Indigestion
  • Diagnosis of irritable bowel syndrome (IBS) or inflammatory bowel disease (IBD)
  • 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 difficult to diagnose because it causes a wide range of symptoms. A gastroenterologist will ask about your symptoms and make a medical examination by probing the abdomen to check for bloating and flatulence. 

A breath test is required to measure the concentration of hydrogen and methane in your breath, which informs the doctor about the severity and location of the SIBO in your gut.

If these results are unclear, you might need blood and/or a urine test for laboratory analysis.  

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 celiac disease or diabetes, should also be treated. SIBO usually occurs as a result of these underlying conditions.  

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