All You Need to Know About SIBO

What is SIBO?

Small Intestinal Bacterial Overgrowth (SIBO) is a condition whereby bacteria in the small intestine multiply excessively spreading beyond the confinements of the small intestine.

What causes it and other complications?

Possible reasons for the disruption of the normal bacterial environment in the small intestine include:

  • Reduced acid secretion in the gut (e.g. Medications such as PPIs, low stomach acid)
  • Compromised immune function (e.g. elderly, people living with HIV)
  • Slowed gastric motility (e.g. gastroparesis, narcotics, moderate alcohol consumption)
  • Anatomical abnormalities (e.g. gastric bypass surgery)
  • Crohn’s disease, Coeliac disease, Irritable Bowel Syndrome (IBS)

What are the symptoms of SIBO?

  • Stomach pain especially after eating
  • Bloating and Gas
  • Diarrhoea (watery)
  • Fatty stool
  • Indigestion
  • Constant feeling of fullness
  • Unexplained weight loss

Are there any Complications?

  • Nutritional deficiencies are common due to the malabsorption of fat, carbohydrates and protein. This means there are vitamins and minerals which may not be properly absorbed in the gut e.g. fat-soluble vitamins (A, D, E and K) and vitamin B12 found in protein rich foods.
  • Mucosal inflammation.

How do you test for it?

If SIBO is suspected, your doctor may request a diagnostic hydrogen -methane breath test. This test requires drinking a sugar lactulose drink and breath tested every 15-20 minutes, for the next 3 hours, by breathing into a balloon. The presence of hydrogen or methane shortly after drinking the solution may be an indicator of the presence of SIBO

How is it treated?

Treatment for SIBO may vary depending on the underlying cause and symptoms:

  • Antibiotics
  • Probiotics (this may help with returning gut bacteria to its normal state however the evidence is not strong enough to prove this)
  • Dietary changes (some people have found relief with specialised diets)
  • Intramuscular vitamin B12 injections

How can food help it?

Nutrition recommendations* aim to improve symptoms and limit the food the bacteria thrive on:

  • Eat small frequent meals to stimulate gastric motility and decrease discomfort caused by eating too much food at a time.
  • Include a variety of foods which contain:
  • Soluble fibre slows down digestion by absorbing fluid and giving your gut more time to absorb the vitamins and minerals it needs
  • Insoluble fibre does not help the bacteria flourish. Their role is to bulk up your stool and make it easier for the contents to pass through the gut.
  • Limit refined and easily fermentable carbohydrates such as refined starches and sugars (e.g. lactose, fructose and other FODMAPs). These forms of carbohydrates are easily broken down and consumed by the bacteria as an energy source resulting in gas, bloating and discomfort. Instead choose vegetables and whole grains which are rich in fibre.


FODMAPs (Fermentable Oligo-, Di-, Mono-Saccharides and Polyols) are short chain carbohydrates which are quickly fermented in the gut, so following a Low FODMAP Diet (LFD) may help alleviate symptoms. An LFD has three main stages:

  1. Restriction of all high FODMAP foods for 8 weeks.
  2. Reintroduction of high FODMAP foods progressively into the diet, monitoring symptoms along the way.
  3. A specialised diet is created, taking into consideration any trigger foods identified during the second phase of this diet.


SIBO is not a simple condition and it can overlap with many gastrointestinal disorders, therefore, it should be carefully diagnosed and treated by a professional.

*Don’t make any drastic changes to your diet without consulting with your Doctor and an Accredited Practising Dietitian.