Irritable bowel syndrome (IBS) is the most common disorder diagnosed by gastroenterologists, with diet being one of the major culprits of symptoms reported by those affected. Although dietary strategies and food supplements are becoming more popular as a means of managing IBS, their efficacy and safety in alleviating gastrointestinal symptoms and quality of life is not always well documented.
A new narrative review, led by Eirini Dimidi and Kevin Whelan from the Department of Nutritional Sciences at King’s College London, updates what recent human studies say about the role of dietary strategies in improving IBS symptoms.
Different sources of evidence (a small number of randomized controlled trials and/or systematic reviews and meta-analyses) suggest the following dietary strategies could aid in improving abdominal discomfort and/or quality of life for those affected by IBS:
- Peppermint oil: can lead to relaxation of smooth muscle in the gastrointestinal tract, with small-intestinal-release formulations appearing to be the most appropriate for improving abdominal pain and discomfort.
- Probiotics: some probiotics (e.g., Lactobacillus plantarum DSM 9843) and non-viable microorganisms (e.g., Bifidobacterium bifidum MIMBb75) have been shown to be effective in improving both general IBS symptoms and their persistence, with a limited effect on improving bloating or flatulence. Although the health benefits of probiotics are strain-specific, it is unclear which single or probiotic combinations are the most effective in improving IBS symptoms.
- Psyllium supplementation: can improve general IBS symptoms and abdominal pain.
- First-line dietary strategies for IBS (i.e., healthy eating, fiber and fluid intake modification, and avoidance of trigger foods such as fatty foods, caffeine, spicy foods and alcohol): can be effective in relieving some IBS outcomes.
- Low FODMAP diet: effective in improving abdominal pain, bloating, flatulence, urgency and stool consistency. However, the low FODMAP diet has been shown to reduce the levels of beneficial gut bacteria and compromise nutrient intake, which means its efficacy and safety in the long term is unknown.
It should be acknowledged, however, that methodological limitations (e.g., high statistical heterogeneity, evidence of publication bias, and a lack of reporting of adverse events in probiotic studies) have been reported in RCTs looking at the role of peppermint oil and probiotics in improving IBS symptoms. As such, that may limit the applicability of the reported findings in the clinical setting.
On the other hand, randomized controlled trials have shown Aloe vera, prebiotic fibers, healthy dietary patterns (e.g., the Mediterranean diet), and a wheat-free diet to be ineffective in improving IBS-related symptoms (abdominal pain, bloating or flatulence) or quality of life.
In conclusion, different sources of evidence in humans show that peppermint oil, specific probiotics, psyllium supplementation, first-line IBS dietary advice and the low FODMAP diet can aid in improving IBS symptoms. To what extent those dietary strategies can be systematically recommended in the clinical setting remains to be seen, as such a recommendation would require support from a significant number of large clinical trials coupled with mechanistic studies disentangling which food components are involved in inducing gut symptoms.
Dimidi E, Whelan K. Food supplements and diet as treatment options in irritable bowel syndrome. Neurogastroenterol Motil. 2020; 32(8):e13951. doi: 10.1111/nmo.13951.