Research shows that patients often seek advice on dietary intervention in order to help their IBS symptoms [1]. Understandably patients want to know which foods to avoid and which are safe to eat.
Over the last few years considerable research has been focused on looking for more specific and effective dietary solutions for IBS. Guidelines from the British Dietetic Association in 2016 suggest two avenues of treatment under the guidance of a dietitian (McKenzie,2016):
- First line approach addressing healthy eating, lifestyle, and looking at recognised dietary triggers such as caffeine, fat, spices and lactose as this may be sufficient to reduce symptoms considerably.
- Second line intervention revolving around the use of the low FODMAP diet. Indeed, the Low FODMAP Diet is now noted on the UK NICE Guidance [2].
The low FODMAP diet
The Low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP) diet was developed by a team from Monash University in Melbourne, Australia. The mechanisms by which these fermentable carbohydrates provoke gut symptoms are due to two underlying physiological processes: firstly, they are indigestible and subsequently fermented by the bacteria in the colon, which leads to gas production. The resulting gas can alter the gut environment and cause hypersensitivity in those who are susceptible to gut pain [4].
Secondly, there is an osmotic effect whereby fermentable carbohydrates increase water delivery to the colon leading to altered bowel habit [5].
There have been several randomized controlled trials and a number of systematic reviews/meta analyses published showing a clear benefit of using the Low FODMAP diet [4,6,7].This has led to fermentable carbohydrate restriction becoming an important consideration IBS treatment. Research indicates that patients using this diet report a marked improvement in symptoms, with up to 70% of patients reporting benefit [13].
Where are FODMAPs found?
| Fermentable carbohydrate | Type | Relevant foods |
|---|---|---|
| Oligosaccharides | Fructans, galacto-oligosaccharides | Wheat, barley, rye, onion, leek, white part of spring onion, garlic, shallots, artichokes, beetroot, fennel, peas, chicory, pistachio, cashews, legumes, lentils and chickpeas |
| Disaccharides | Lactose | Milk, custard, ice cream and yogurt |
| Monosaccharides | Free fructose (fructose in excess of glucose) | Apples, pears, mangoes, cherries, watermelon, asparagus, sugar snap peas, honey, high-fructose corn syrup |
| Polyols | Sorbitol, mannitol, maltitol, xylitol | Apples, pears, apricots, cherries, nectarines, peaches, plums, watermelon, mushrooms, cauliflower, sugar free chewing gum/mints/sweets |
A gluten-free diet for IBS
Research suggests that some patients with IBS (where coeliac disease has been excluded) find symptom relief when following a gluten free diet [18-21]. The reasons behind this observation are hotly debated amongst experts in the field and may be related to the presence of non-coeliac gluten sensitivity which can result in identical gut sumptoms to those found in IBS patients. It is also plausible that symptom improvement upon commencement of a gluten free diet is simply related to the concurrent reduction in the FODMAP content of the diet, namely a reduction in fructans found in wheat, barley and rye [22]. When considering the use of a gluten free diet for the management of IBS it is vital to ensure coeliac disease has been excluded prior to the removal of wheat/ gluten from the diet.
Probiotics
Research showing the benefits of probiotics in the treatment of IBS is conflicting and may be hampered by the fact that the human gut can be populated by any of 1000-1150 different bacterial species [23], and yet most probiotic supplements contain no more than a handful of species. A recent RCT showed the first evidence that the, “effect of the low FODMAP diet on bifidobacteria can be modified by adjunctive probiotic therapy (Staudacher,2017). However, a recent systematic review of the use of probiotics in IBS concluded that they were, “unlikely to provide substantial benefit to IBS symptoms (McKenzie, 2016). Nevertheless, some probiotics have shown benefit and current NICE guidance [2] recommends that patients with IBS who choose to try probiotics should be advised to consume them for at least 4 weeks whilst monitoring the effect on symptoms.
Pharmacological and alternative therapies
Pharmacological treatment options for the management of IBS should be based on symptom nature and severity, these may include antispasmodics, laxatives, anti-diarrhoeal agents, tri-clyclic antidepressants and selective serotonin reuptake inhibitors. Side effects from pharmacological therapies are common and symptom relief may be variable. Patients who do not respond to dietary or drug management of their symptoms may benefit from psychological interventions including hypnotherapy [2].