Dr. Schär Institute

Eighty six studies were critically appraised to generate 46 evidence statements, 15 clinical practice recommendations and 4 research recommendations (outlined below). The evidence reviewed was graded using the Practice-based evidence in nutrition (PEN) grading criteria (level A, supported by good evidence to level D, evidence is limited). A recommendation related to fluid intake was not developed as a result of insufficient evidence, however, despite this lack of evidence, a gradual increase in fluid intake is recommended up to a total of 1.5-3l/day to improve stool frequency in IBS-C. The IBS dietary treatment algorithm was updated and simplified to provide only first-line (healthy eating, provided by any healthcare professional) and second-line (low FODMAP advice to be provided by a dietitian) advice. Third line advice, previously recommending elimination or empirical diets, was removed from the updated guidelines.
 
Clinical Practice Recommendations

1. Healthy eating and lifestyle: 

• Alcohol – Assess intake and screen for signs of binge drinking. Ensure Alcohol intake is in keeping with safe national limits (2016) PEN grade C
• Caffeine – Insufficient evidence to make a recommendation (2016) PEN grade D. Assess Caffeine intake and if related to symptoms, consider reducing intake.
• Spicy Food – If related to symptoms, assess spicy food intake and trial restriction (2016) PEN grade C. It is useful to assess other components of spicy meals that may contribute to symptoms (e.g. FODMAPs in onion & garlic).
• Fat – If related to symptoms during or after eating, assess fat intake and ensure it is in line with national healthy eating guidelines (2016) PEN Grade C
• Dietary Habits – Insufficient evidence to make a recommendation (2016) PEN Grade D.

Despite lack of evidence, assess dietary habits and provide advice re how to achieve a healthy, balanced diet with regular meal pattern. Take time over meals, sit down to eat, chew thoroughly and don’t eat late at night.

2. Restricting milk and dairy products: 

• In individuals with IBS where sensitivity to milk is suspected and a lactose hydrogen breath test is not available or appropriate, a trial period of a low lactose diet is recommended. This is particularly useful in individuals with an ethnic background with a high prevalence of primary lactase deficiency (2012) PEN Grade D
• Use a low lactose diet to treat individuals with a positive lactose hydrogen breath test (2012) PEN Grade D 

3. Dietary fibre modification: 

• Avoid using dietary supplementation of wheat bran to treat IBS. Individuals should not be advised to increased their intake of wheat bran above their usual dietary intake (2012) PEN Grade C
• For individuals with IBS-C, try dietary supplementation of linseeds of up to 2 tablespoons per day for a 3 month trial. Improvements in constipation, abdominal pain and bloating from linseed supplementation may be gradual (2016) PEN Grade D 

4. Fermentable carbohydrates: 

• For individuals with IBS, consider a low FODMAP diet to improve abdominal pain, bloating and/or diarrhoea for a minimum of 3 or 4 weeks. If no symptom improvement occurs within 4 weeks of strict adherence to the diet, then the intervention should be stopped and other therapeutic options considered (2016) PEN Grade B
• There may be individual tolerance levels to FODMAPs. A planned and systematic reintroduction challenge of foods high in FODMAPs will identify which foods can be reintroduced to the diet and what individual tolerance levels are (2016) PEN Grade D 

5. Gluten: 

• At this time no recommendation can be made to treat IBS symptoms with a gluten-free diet (2016) PEN Grade D 

6. Probiotic products to improve IBS symptoms (NB – 19 separate evidence statements regarding the use of probiotics in the management of IBS are provided elsewhere*): 

• Advise that probiotics are unlikely to provide substantial benefit to IBS symptoms. However, individuals choosing to try probiotics are advised to select one product at a time and monitor the effects. They should try it for a minimum of 4 weeks at the dose recommended by the manufacturer (2016) PEN Grade B
• Taking a probiotic product is considered safe in IBS (2016) PEN Grade B 

7. Elimination diets/ food hypersensitivity: 

• Non-specific elimination diets are no longer valid to improve IBS symptoms (2016) PEN Grade D

Research Recommendations

1. Dietary Fibre

There is a need for well-designed/ powered RCTs to assess the effects of dietary fibre intakes of at least 30g/day in the treatment of IBS-C, with long term follow-up. Should the fibre recommendations for IBS sufferers differ from that of the general population? Can these individuals increase their intakes to meet healthy eating recommendations?

2. FODMAPs

Well-designed/ powered RCTs should aim to assess IBS symptom profiles, long-term follow-up, safety and optimal education delivery. Dietary components that affect gut motility and microbiota, effectiveness compared to or combined with other therapies, predictors of response to a low FODMAP diet, success of alternative delivery options to dietitian-led counselling in terms of safety, nutritional adequacy, acceptability and clinical/ cost effectiveness.

3. Gluten

Well-designed/ powered RCTs should differentiate between gluten sensitivity and FODMAPs and establish a clear definition of the difference in symptom profile between the two conditions. Dietary intake should also be measured.

4. Probiotics

Well-designed/ powered RCTs should consider dietary components that affect gut motility and microbiota and measure dietary intake.

*McKenzie Y, Thompson J, Gulia P et al. British Dietetic Association systematic review of systematic reviews and evidence-based practice guidelines for the use of probiotics in the management of irritable bowel syndrome in adults (2016 update). J Hum Nutr Diet (2016) doi: 10.1111/jhn.12386

Link to original paper