Effectiveness of Dietary Intervention in Irritable Bowel Syndrome – Results of a Network Meta-Analysis
A low FODMAP diet is often recommended to alleviate symptoms of irritable bowel syndrome (IBS). Although several randomized studies have been conducted to assess the effectiveness of this diet, a systematic evaluation has yet to be available, and individual studies have used various control interventions. Therefore, an international team of researchers decided to prepare a systematic literature review with a network analysis, recently published in the journal Gut.
Nutrition in IBS Patients
Up to 80% of IBS patients report symptoms associated with the consumption of certain foods. One of the most frequently used dietary interventions is the restriction of foods containing fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs). FODMAPs are present, for example, in certain types of fruits, vegetables, legumes, or artificial sweeteners.
The dietary intervention usually consists of a period of complete elimination of FODMAP-containing foods for approximately 4–6 weeks, followed by a gradual reintroduction period to the patient's regular diet to determine individual tolerance to FODMAPs and to design a personalized diet. Numerous clinical studies in the past 10 years have shown that the complete elimination of FODMAPs effectively reduces IBS symptoms. However, these clinical studies employed various different alternative or control interventions, making it unclear which intervention is the ideal comparator.
The authors of the present study therefore decided to conduct a network meta-analysis to assess not only the effectiveness of a low FODMAP diet on overall and individual IBS symptoms but also the relative effectiveness of the compared interventions.
Methodology of the Meta-Analysis
The authors searched for randomized controlled clinical trials published up to April 2021 that evaluated the effectiveness of a low FODMAP diet on improving overall and individual IBS symptoms (abdominal pain, bloating, and abdominal distension and bowel habits). The data were pooled using a random-effects model, and effectiveness was evaluated as the pooled relative risk (RR) of intervention failure, i.e., failure to reduce IBS symptoms, with 95% confidence intervals (CIs). Interventions were then ranked according to their p-scores.
Results
Thirteen clinical trials with data from 944 patients were included in the meta-analysis. The low FODMAP diet ranked first among the interventions in terms of reducing overall IBS symptoms compared to regular diets (RR of no improvement in symptoms 0.67; 95% CI 0.48–0.91; p-score 0.99) and showed superiority over all other assessed interventions. It also led to the greatest reduction in abdominal pain and bloating/distension. It was also ranked first for effectiveness in normalizing bowel habits, but did not achieve superiority over other interventions.
Conclusion and Discussion
In the presented network meta-analysis, the low FODMAP diet proved to be the most effective in terms of all assessed parameters for reducing IBS symptoms. Its benefit was greater even compared to dietary recommendations for IBS patients in primary care from the British Dietetic Association (BDA) or the UK's National Institute for Health and Care Excellence (NICE).
However, it should be noted that the majority of the evaluated studies were conducted in secondary or tertiary care settings and did not assess the impact of reintroducing FODMAP-containing foods into the patient's diet or individualizing the diet on IBS symptoms. They also did not include assessments of using treatments for IBS symptoms, such as Aloe vera extract, which has been shown to have a beneficial effect on symptoms (p = 0.02 compared to placebo in a meta-analysis of 3 clinical studies).
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Sources:
1. Black C. J., Staudacher H. M., Ford A. C. Efficacy of a low FODMAP diet in irritable bowel syndrome: systematic review and network meta-analysis. Gut 2022 Jun; 71 (6): 1117–1126. doi: 10.1136/gutjnl-2021-325214.
2. Hong S. W., Chun J., Park S. et al. Aloe vera is effective and safe in short-term treatment of irritable bowel syndrome: a systematic review and meta-analysis. J Neurogastroenterol Motil 2018; 24 (4): 528–535, doi: 10.5056/jnm18077.
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