According to a recent systematic review, elimination diets cannot be strongly recommended to patients with irritable bowel syndrome until further evidence becomes available.
Because efficacy data from randomized controlled trials of dietary interventions in patients with IBS had not been systematically evaluated, Paul Moayyedi, MBChB, PhD, MPH, FACG, from McMaster University in Ontario, Canada, and colleagues, identified 17 randomized controlled trials of elimination diets involving 1,568 IBS patients published up to December 2013.
Three RCTs involving 230 patients met eligibility criteria, but each assessed different interventions, so a meta-analysis was not performed. The primary outcome of interest was global improvement in IBS symptoms or improvement in abdominal pain if global symptoms were not reported.
One eligible trial evaluated gluten-free diet in 39 patients with IBS (89% female) in whom celiac disease was ruled out and whose symptoms improved on a gluten-free diet. Patients were instructed to continue gluten-free diet and were randomly assigned to receive a gluten-free muffin and gluten-free bread or the same supplement spiked with 16 g of gluten per day for 6 weeks.
Symptoms significantly worsened in the gluten group each week, and 68% reported inadequately controlled symptoms compared with 40% of the placebo group (P = .0001). Had the authors used a Fisher’s exact test rather than a generalizing estimating equation, the results would not have been statistically significant, Moayyedi and colleagues wrote, concluding that “the relative risk of symptoms occurring in the group challenged with gluten was 1.71 (95% CI, 0.91-3.62) according to these proportions.”
Low FODMAP diet
One eligible trial randomly assigned 41 patients with IBS to low fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP) diet or their normal diet for 4 weeks. A trend for improvement of all symptoms was observed except for constipation and diarrhea. The low FODMAP group was also found to have significantly reduced bifidobacteria in their fecal microbiota compared with controls. Overall, 68% of the low FODMAP group reported adequate symptom control compared with 23% of controls (P = .005), “but it is important to emphasize that this trial had a high risk of bias, as participants and researchers were not blinded and were aware who was on a low FODMAP diet,” Moayyedi and colleagues wrote.
Other exclusion diets
One eligible trial evaluated 150 patients with IBS from a single center who underwent immunoglobulin G antibody testing to 29 food antigens and were then randomly assigned to a diet excluding foods to which they were intolerant (primarily milk, yeast, egg or wheat) or a sham diet for 12 weeks. Improved symptoms were reported by 28% of the treatment group compared with 17% of controls, which was not a significant difference. Eleven patients from the treatment group and three from the control group withdrew because the diet was too restrictive. If only the 32% of the treatment group who strictly adhered to their diet were analyzed, then their “mean IBS severity score was statistically significantly lower,” Moayyedi and colleagues wrote.
“Despite promising data on the efficacy of dietary restriction in IBS, we suggest that this approach cannot be recommended strongly until more evidence is accumulated,” they concluded.” – by Adam Leitenberger
Disclosure: The researchers report no relevant financial disclosures.