Irritable bowel syndrome (IBS) is a chronic functional gastrointestinal disorder affecting one in five Australians. It can be debilitating and significantly impact quality of life. It is far more common in females. Symptoms include bloating, abdominal cramps, flatulence, diarrhoea and/or constipation.

The exact cause of IBS remains unknown. Common triggers such as food intolerances, inadequate fibre intake, visceral hypersensitivity, alterations in gut motility and microbiome, infection and certain medications may exacerbate symptoms in genetically predisposed individuals.

Charlyn Ooi, Dietitian, Ardross

Charlyn Ooi, Dietitian, Ardross

Although the low Fermentable Oligo-, Di-, Mono-saccharides and Polyols (FODMAP) diet has been widely accepted as an effective first-line dietary treatment strategy for the management of IBS, it is certainly not a diet for life. An individualised dietary approach is imperative for optimal patient outcomes.

FODMAPs are short-chain carbohydrate sugars poorly absorbed and subsequently fermented in the large intestines, resulting in luminal distension, diarrhoea, excess wind, cramping or constipation. Common high FODMAP foods include garlic, onion, wheat, mushrooms, apples, watermelon, lentils and milk.

Data from Monash University revealed that a temporary reduction of FODMAPs in the diet improved overall gastrointestinal symptoms by 86%. Following the initial two to six weeks ‘Elimination Phase’, the individual undertakes a structured challenge protocol in the ‘Challenge Phase’ to identify their personal triggers. The final step is the ‘Personalisation Phase’, where tolerated FODMAP groups are reintroduced.

Challenges of the low FODMAP diet

The low FODMAP is not a ‘No FODMAP’ diet. The concept of this diet involves a reduction of FODMAP load to alleviate symptoms. An internet search will reveal a range of often outdated and conflicting FODMAP food lists. Caution needs to be applied when interpreting these food lists as they can create more confusion, lead to unnecessary food restrictions and nutritional gaps.

The low FODMAP diet is a specialised area of nutrition best undertaken with the guidance and support of a dietitian specialising in IBS, who plays an important role in supporting the patient to implement the diet successfully, identify their individual triggers and evaluate tolerance thresholds. Patients with complex medical issues including multiple allergies or intolerances, diabetes or children will require comprehensive support.

Despite being a highly effective treatment strategy for IBS, a low FODMAP diet is not recommended long-term. The effects of long-term FODMAP restriction remains unclear but recent studies have observed negative changes in gut microbiome diversity.

A probable cause is the reduction in high fibre foods that also contain prebiotics and resistant starch, limiting fuel for the gut bacteria. Moreover, it is uncommon for someone to react to all the high FODMAP groups. Ideally, we are looking for the least restrictive diet possible while maintaining good symptom control.

Key messages

  • The low FODMAP diet is highly effective for IBS
  • Individualised dietary and lifestyle modification advice is imperative
  • A low FODMAP diet is not for life

References available on request.

Questions? Contact the editor.

Author competing interests: nil relevant disclosures.

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