Irritable bowel syndrome (IBS) is one of the most common, un-talked about, disorders affecting people in the modern world today. The global prevalence of IBS is estimated to be 11.2%, with statistics specific to Australia showing that more than 1 in 5 (20%) people suffer from this unkind condition. Characterised by abdominal discomfort and irregular bowel motions, this functional disorder further impacts mental and social health, leaving individuals frustrated and confused on how to manage it. Fortunately, dietary strategies are the preferred and first-line treatment for IBS, with specific interventions showing significant improvements in more that 75% of IBS sufferers.

What is IBS?

IBS is a digestive disorder that is characterised by chronic abdominal bloating, abdominal discomfort and altered bowel habits. Digestive symptoms are often unique for each IBS sufferer and can include: excess flatus, abdominal cramping, diarrhoea, constipation or a combination of diarrhoea and constipation. Abdominal discomfort is the key characterising feature of IBS.

IBS symptoms

  • Abdominal discomfort/pain

  • Bloating

  • Flatulence

  • Diarrhoea

  • Constipation

  • Urgency to go

  • Incomplete evacuation

IBS is classified as a functional disorder, meaning the above-mentioned symptoms occur in the absence of other structural or biochemical abnormalities.

Dietary strategies to manage IBS

The following dietary strategies have shown some evidence in improving abdominal discomfort:


Probiotics are live microorganisms that when administered in adequate amounts confer health benefits to the host. They are found in fermented foods such as yoghurt, kimchi and kefir, as well as in supplements. Probiotics may improve IBS symptoms by altering your gut microbiota diversity as well as their metabolite production. Probiotics may also interact with your intestinal immune system, enteric nervous system and central nervous system. These factors in turn may modulate your gut motility (movement of food/stools through your intestinal tract), inflammation and visceral hypersensitivity. Visceral hypersensitivity is a predominant causal factor for abdominal discomfort and pain in IBS sufferers.

Evidence suggests that specific probiotic strains or probiotic combinations may improve global IBS symptoms and persistence of IBS symptoms, but not bloating or flatulence, in some individuals. Unfortunately, evidence is still unclear on which strains or strain combinations are effective.

Peppermint oil

It has been shown to modulate histaminergic and cholinergic receptors in the gut, plus exhibit k-opioid activity, serotenergic antagonism and anti-inflammatory effects. Most importantly, it's active ingredient "L-menthol" leads to intestinal smooth muscle relaxation, potentially reducing abdominal discomfort.

A systematic review and meta‐analysis of 12 RCTs, including 835 IBS patients, concluded peppermint oil to be safe and effective in improving IBS symptoms. It showed overall improvements in both global symptoms and abdominal pain, compared to placebo.

Take note, peppermint oil can however influence heartburn and reflux, due to it's effects on relaxing the lower oesophageal sphincter.

Fibre & prebiotics

Dietary fibre is the part of plant materials that resists digestion. Soluble fibre softens yours stools by attracting water into your bowels. Insoluble fibre adds bulk to your stools, assisting them to move through your GI tract more efficiently. Prebiotic fibres are fermented by your gut microbiota, in turn increasing your gut microbes health, diversity and vitality. Your stools are predominantly made of bacteria (dead and alive); therefore the more fibre you get, the healthier your stool habits. Mind-blowing fact: less than 1 in 5 adults in Australia meet recommendations for fibre intake.

In a systematic review and meta‐analysis of 22 RCTs, soluble fibre significantly improved global IBS symptoms and abdominal pain, however insoluble fibre made no improvements.

Furthermore, your gut microbiota very likely contribute to the pathophysiology of your IBS, therefore modulation of your microbiota with prebiotics may play a role in your IBS symptom control. The key is getting the right types and the right amounts of prebiotics. For example, research has shown that prebiotic doses of 6 grams or less per day improved flatulence in IBS sufferers. Further to this, flatulence was improved specifically with non-insulin-type fructans. In comparison, IBS symptoms were significantly exacerbated (worsened) with inulin-type fructans, as well as large doses.

In summary, IBS symptoms can likely be improved by consuming both both soluble fibres and prebiotics fibres, however definition is in the detail, meaning the right types and right amounts must be individualised for each unique person.

Gut irritant avoidance

Gut irritants include, alcohol, coffee, caffeine, fatty and greasy foods, emulsifiers, artificial sweeteners, ultra-processed foods, antibiotics and other medications. You can read more here.

FODMAP modification

FODMAPS stands for: Fermentable, Oligosaccharides, Disaccharides, Monosaccharides and Polyols. These are types of short chain carbohydrates that resist digestion and are rapidly fermented by bacteria in your large intestine. FODMAPS increase small bowel water content as well as microbiota-mediated colonic gas production.

FODMAPS induce gut symptoms in people with IBS.

FODMAP modification is a three phased approach, which includes:

  • Phase 1: The Low FODMAP diet - Elimination of all moderate to high FODMAP containing foods from your diet.

  • Phase 2: FODMAP challenges - Re-introduction and tolerance testing of low and high dose FODMAP subgroups.

  • Phase 3: Personalised FODMAP diet - Modifying your diet to be as close to your normal eating, as liberal, and as nutritionally complete, as possible, with consideration of your FODMAP intolerances and tolerances.

Research shows that more than 3 in 4 people with IBS experience significant symptom improvement on a low FODMAP diet, including improvements in abdominal pain, bloating, flatulence, urgency, and stool consistency.

Despite the major benefits of a low FODMAP diet, a potential negative impact on gut microbiota health is the reduction in gut bacteria diversity; particularly Bifidobacteria concentrations. This is in relation to a reduced consumption of prebiotic foods, plus less varied diet. Further to this, a low FODMAP diet can lead to a lower fibre, iron and calcium intake. It is therefore imperative to work with a Dietitian who specialises in IBS to ensure nutritional adequacy, as well as the long term health of your gut.