The gut microbiome and IBS

Author: Bianca Maree Harrington, Accredited Practising Dietitian; Lead Microba Microbiome Coach.

1 July 2020


Irritable Bowel Syndrome (IBS) is a common disorder of the gut-brain axis estimated to impact one in five Australians at some point in their life and is generally more common in women than it is in men1.

IBS is a complex condition that often requires a combination of treatment and management strategies to effectively manage a patient’s symptoms. No two cases of IBS will ever present identically, and it is likely that the management strategies involved will differ between patients.

What is IBS and how is it diagnosed?

The diagnosis of IBS is often based on symptoms after the exclusion of other possible gastrointestinal diseases. IBS can be categorised into four major subtypes depending on the predominant stool pattern:

  • IBS with constipation (IBS-C)
  • IBS with diarrhea (IBS-D)
  • IBS with mixed bowel habits (IBS-M)
  • Unclassified IBS (IBS-U).

It should be noted that these subtypes are not considered distinct, and instead represent the spectrum of clinical presentations that vary in quantity, intensity, and severity of symptoms between patients.

What are the main causes of IBS?

Although the precise cause of IBS is still unknown, it is thought that IBS involves a complex interaction of many factors, including microbial dysbiosis, visceral hypersensitivity, altered mucosal immune function and changes to the brain’s regulation of gut function2.

Around 9% of IBS is thought to be post-infective IBS which was triggered by a gut infection3. Age, genetics, diet, and stress are also known to play a role in the onset of symptoms associated with IBS2.

What are the known associations between the gut microbiome and IBS?

The gut microbiome is associated with many areas of health, including gastrointestinal health, and associated medical conditions. A growing body of evidence is looking to understand how the gut microbiome differs in people who have IBS compared with those who do not.

Emerging research is revealing recurring patterns are evident in the microbiomes of individuals who have IBS4-6. These include:

  • Reduced microbial diversity
    Microbial dysbiosis in IBS is predominately characterised by a loss of diversity and increased temporal instability. Factors which are thought to contribute to dysbiosis are poor diet, stress, infection, antibiotic usage, immune activation, and low-grade inflammation4.
  • Reduced potential to produce butyrate and propionate
    Large metagenomic studies have shown that the microbiome of patient’s with IBS have a lower potential to produce the important Short Chain Fatty Acids (SCFAS) butyrate and propionate. These SCFAs play vital roles in maintaining gut barrier function, reducing inflammation and regulating gut motility.
  • Low levels of Akkermansia muciniphilia
    Studies have observed low levels of the species Akkermansia muciniphilia in the gut microbiome of patients with Irritable Bowel Syndrome. This species lives in the mucus layer of the intestine and plays an important role in regulating mucus turnover.
  • Enriched levels of pro-inflammatory bacteria
    Patients with IBS have also been observed to have increased levels of pro-inflammatory bacteria. The scientific literature and Microba’s own database have consistently highlighted the protein-degrading bacteria Eggerthella lenta and Rumminoccus gnavus as being enriched in the IBS microbiome.

The value of gut microbiome analysis for IBS sufferers.

As we now know, significant microbial dysbiosis is seen in IBS sufferers. However, the characteristics of the dysbiosis will differ patient to patient. Using metagenomic analysis we can understand the dysbiosis allowing us to tailor the intervention for the promotion of microbial balance.

Every customer report presents differently, so no two Microba Insight™ reports will ever be identical. Gut microbiome analysis may provide additional insights to consider when establishing an individualised treatment plan for patients with IBS. Microba’s comparative tool also enables practitioners to monitor changes to their patient’s gut microbiome over time.

Metagenomics gut microbiome

Interested in knowing more about metagenomics? Learn more.


About the Author



Bianca Maree Harrington

Bianca Maree is a specialist Accredited Practising Dietitian and Lead Microbiome Coach at Microba, with an expertise in managing food intolerances associated with Irritable Bowel Syndrome (IBS). She is passionate about furthering our understanding of how the microbiome and other lifestyle factors can impact IBS sufferers, and how an integrative approach is required to better manage this condition.


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