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Irritable bowel syndrome (IBS) and probiotics – The gut brain axis

Irritable bowel syndrome (IBS) and probiotics – The gut brain axis

What is IBS?

IBS is a functional gastrointestinal disorder affecting up to one quarter of the global population and accounting for up to half of all gastrointestinal related medical visits. IBS is part of a disturbed signalling between the central nervous system and the gut commonly known now in the literature as the “gut brain axis”.

Latest research implicates the gut microbiota (bacteria in living in the gut) as a causative factor in the development of IBS. Disturbance in the composition of the beneficial bacteria residing in the gut can lead to IBS symptoms such as constipation, diarrhoea, bloating and abdominal pain.

If you are experiencing gastrointestinal symptoms you should see your doctor for a diagnosis to exclude other causes such as inflammatory bowel disease and coeliac disease before assuming it is IBS. IBS can be further classed as either diarrhoea dominant, constipation dominant or mixed.

Who lives in your gut is affected by your diet, environment, medications, where you live and age. When the delicate population is out of balance this is known as dysbiosis.

What is a probiotic? The World Health Organisation provide the following definition: “live microorganisms, which when taken in adequate amounts, confer a health benefit on the host”.

Interestingly the word probiotic means “for life” in latin. Humans have a long history of consuming fermented foods.

Why are probiotics a good thing?

Here’s how they work:

  • Competitive inhibition of pathogenic bacteria
  • Support the function of the intestinal barrier by improving the integrity of the tight gap junctions
  • Modulation of the immune system
  • Synthesis of neurotransmitters including serotonin and gamma-aminobutyric acid (GABA), thereby contributing to the gut–brain axis

What about Prebiotics?

In short, prebiotics are food for probiotics which are beneficial and healthy bacteria that live in our guts. Inulin, beta glucan and fructo-oligosaccharides are the key prebiotics to include.

Inulin is resistant to digestion in the small intestine allowing it to travel to the large bowel where Bifidobacterium and lactic acid producing bacteria ferment it and increase the population of these bacteria. Short chain fatty acids (SCFAs) are made as a result which are a key energy source for colon cells.

Beta glucan (in cereal grains) feed Bifidobacterium and Lactobacillus, and Bifidobacterium infantis has been shown to increase SCFAs in response to fermentation of beta glucans.

(FOS) also travel to the large bowel where they increase Bifidobacterium, SCFAs and faeces improving bowel motility.

How do I know which probiotic I need?

Probiotics are not all the same, there is no one size fits all. Here are the key factors your naturopath will consider:

  • “Strain specificity” – different strains within a species may exert different therapeutic actions which can also be affected by where the strain was sourced from eg. human or dairy derived
  • Diversity – the number of species and the range of strains
  • Form of the product – eg. Capsule, powder, food
  • Dose – colony forming units (CFU) which can range greatly between products from 100 million to 450 billion CFU per dose
  • Prebiotic content – whether there are prebiotics present in the formula

Probiotics are a very hot topic in the scientific literature at the moment and there is new and exciting research being conducted all the time! There are different strains for different conditions and you should always seek the guidance of a qualified health practitioner before self-prescribing any complementary medicines as they also may interact with each other and or medications.

Other factors to consider in IBS:

  • The diversity of the microbiome is affected by caesarian birth in comparison to vaginal birth, formula feeding in comparison to breast feeding
  • Research suggests an overall defecit in Bifidobacterium and Lactobaccilli species and an increase in Gammaproteobacterium species in IBS
  • Use of antibiotics have been associated with IBS
  • Diarrhoea dominant IBS and post infectious IBS are associated with intestinal hyperpermeability that can disturb immune function
  • Post infectious IBS is associated with the following pathogens: Campylobacter, Salmonella, Escherichia coli, and Shigella species (Proteobacteria)
  • IBS is associated with mental illness due to the gut brain axis, and the effect of the microbiome on the central nervous system (CNS)
  • Fibre serves as a prebiotic for both good and bad bacteria therefore increasing prebiotic fibre can temporarily aggravate existing dysbiosis
  • The Mediterranean diet has been associated with enhanced population numbers of bacteria and is a high fibre, high plant food/antioxidant and low red meat diet compared to the Western diet which is high in animal fat and protein and along-side a gluten free diet is associated with a lower number of bacteria and a higher number of enterobacteria
  • IBS and non-coeliac gluten sensitivity have similar symptomatology
  • Research has indicated that one month on a gluten-free diet raised E.coli and Enterobacteriaceae and saw a decline in Lactobacilli
  • Various food additives including artificial sweeteners and emulsifiers such as polysorbate and carboxymethylocellulose found in ice cream change the microbiome composition and create inflammation


Beneficial foods to support the microbiome

Prebiotic Inulin Food Sources Fructo-oligosaccharides (FOS) Food sources
Leek Honey
Jerusalem artichoke Onion
Asparagus Wheat
Onions Garlic
Garlic Banana


Manipulation of your diet will be a key part of your treatment plan as your naturopath identifies any underlying food aggravators with a food/symptom diary. Gut symptoms such as bloating, diarrhoea, constipation and abdominal pain are a message from your body that something is out of balance. You don’t have to live with these unpleasant symptoms. Your naturopath can formulate a personalised treatment plan with herbal medicines tailored to suit your individual needs.

Book your initial naturoapthy consultation online today!


Harper A, Naghibi MM, Garcha D. 2018, The Role of Bacteria, Probiotics and Diet in Irritable Bowel Syndrome. Foods. 26;7(2). pii: E13. doi: 10.3390/foods7020013. Review. PMID:29373532

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