SIBO stands for Small Intestine Bacterial Overgrowth, and it’s a really common cause of IBS (irritable bowel syndrome). Our gut is full of bacteria – and that’s a really good thing!

The bacteria in our gut help us to:

  • Break down food
  • Feel energized
  • Have a strong immune system
  • Regulate our inflammatory responses
  • Have good mental health
  • Support mood regulation

But, what’s really important is having the right bacteria in the right amounts in the right places.

Most of our good bacteria should be sitting in our large intestine. Our small intestine does contain some bacteria, but in considerably lower amounts than our large intestine. In SIBO, the amount of bacteria in the small intestine becomes excessive, leading to a myriad of digestive symptoms.

What are the symptoms of SIBO & IBS?

  Abdominal pain  
Flatulence Flatulence Yes
Bloating Bloating Yes
Gas Gas Yes
Abdominal discomfort Abdominal discomfort Yes
Diarrhea/constipation* Diarrhea/constipation  
Acid reflux/heart burn    
Food intolerances/allergies    


IBS is often diagnosed when conditions like inflammatory bowel disease (IBD) and coeliac disease have been ruled out, in other words, when they aren’t quite sure why you’re experiencing digestive upset. However, SIBO is often not considered by your local GP. As you can see, the symptoms of SIBO and IBS are closely related. Some studies have identified that up to 84% of participants with IBS actually test positive for SIBO. There is some debate in the medical community as to whether or not this is significant as in other studies this number is much lower, or is even non-existent.

What causes SIBO?

We always want to find out why the SIBO occurred in the first place. After all, if we eradicate the bacterial overgrowth without fixing the source of the bacterial overgrowth, it’s really likely that the SIBO will recure. There are multiple mechanisms of action that can affect the regulation of bacteria in the small intestine, causing the development of SIBO including:

  • Disturbances in gut-immune function
  • Changes in the structure of the gastrointestinal tract which may occur:
    • After surgery
    • After radiation
    • Due to Crohn’s disease
    • Due to medication use
    • As a result of endometrial lesions in endometriosis
  • Low gastric acid (far more common than you may think)
  • Abnormalities of the migrating motor complex (MMC) which ‘sweeps’ the GI tract to clean out debris between meals & during periods of fasting
  • Abnormalities to peristalsis, the wave-like motion that contracts the stomach to assist with digestion

In consultations, we aim to identify which of the above causes is the culprit for the development of the SIBO in the client sitting in front of us.

Who is at risk of SIBO?

People with the following conditions are at a higher risk of developing SIBO:

  • IBS
  • Metabolic disorders (including diabetes)
  • Coeliac disease
  • Chronic diarrhea
  • Hypothyroidism or Hashimoto’s, due to delayed gastric emptying
  • Fibromyalgia
  • Chronic fatigue syndrome
  • Diverticulitis
  • And the ageing population, due to changes in digestive function that occur with age

How is SIBO diagnosed?

SIBO is most commonly diagnosed by a breath test. Typically, the first line of testing is typically a lactulose breath test or, for more comprehensive testing a lactulose, glucose & fructose breath test. The breath test captures whether or not hydrogen, methane or combined hydrogen-methane gasses are present, elevated & if they fluctuate at appropriate times to suggest SIBO. Stool testing is not an accurate way of testing for SIBO, however it can be helpful in getting a larger understanding of what’s happening in the gut as a whole, and certain results do suggest that SIBO testing is warranted (if stool testing is completed prior to SIBO testing).

Is SIBO the cause of IBS?

SIBO can be the cause of IBS. There are also other bacterial and fungal overgrowths in the gut that can be contributing to IBS symptoms. In fact, there are multiple different potential causes of IBS including nutrient deficiencies, stress, dietary choices & leaky gut. Working with Katie or Dani in one on one consultations is a great way to get to the bottom of what is causing your IBS.

I have IBS & am thinking it might be SIBO – where to from here?

If you’re in Australia, or more specifically in Croydon, Victoria book in for a free 15 minute discovery call. Naturopathy is really well suited to IBS & SIBO becasue we are able to use herbal medicine to support the microbial balance in the small intestine to reduce the bacterial overgrowth in SIBO and to stimulate the MMC & peristalsis to reduce the recurrence of SIBO. If you feel like you’re a good fit with Katie, the next step is to book in for an initial Naturopathic consultation and start your gut healing journey.

*SIBO with constipation is now considered to be a diagnosis of its own.


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