Background & aims

Low adherence to Mediterranean diet (MD) has been shown to be associated with a higher prevalence of irritable bowel syndrome (IBS), but its association with IBS symptoms is not established. We aim to assess the association between MD and IBS symptoms, identify components of MD associated with IBS symptoms, and determine if a symptom-modified MD is associated with changes in the gut microbiome.

Methods

One hundred and six Rome +IBS and 108 health control participants completed diet history and gastrointestinal symptom questionnaires. Adherence to MD was measured using Alternate Mediterranean Diet and Mediterranean Diet Adherence Screener. Sparse partial least squares analysis identified MD food items associated with IBS symptoms. Stool samples were collected for 16S ribosomal RNA gene sequencing and microbial composition analysis in IBS subjects.

Results

Alternate Mediterranean Diet and Mediterranean Diet Adherence Screener scores were similar between IBS and health control subjects and did not correlate with Irritable Bowel Syndrome Severity Scoring System, abdominal pain, or bloating. Among IBS participants, a higher consumption of fruits, vegetables, sugar, and butter was associated with a greater severity of IBS symptoms. Multivariate analysis identified several MD foods to be associated with increased IBS symptoms. A higher adherence to symptom-modified MD was associated with a lower abundance of potentially harmful Faecalitalea, Streptococcus, and Intestinibacter, and higher abundance of potentially beneficial Holdemanella from the Firmicutes phylum.

Conclusions

A standard MD was not associated with IBS symptom severity, although certain MD foods were associated with increased IBS symptoms. Our study suggests that standard MD may not be suitable for all patients with IBS and likely needs to be personalized in those with increased symptoms.

Background & aims

Altered fecal microbiota have been reported in irritable bowel syndrome (IBS), although studies vary, which could be owing to dietary effects. Many IBS patients may eliminate certain foods because of their symptoms, which in turn may alter fecal microbiota diversity and composition. This study aimed to determine if dietary patterns were associated with IBS, symptoms, and fecal microbiota differences reported in IBS.

Methods

A total of 346 IBS participants and 170 healthy controls (HCs) completed a Diet Checklist reflecting the diet(s) consumed most frequently. An exclusion diet was defined as a diet that eliminated food components by choice. Within this group, a gluten-free, dairy-free, or low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols diet was further defined as restrictive because they often are implicated in reducing symptoms. Stool samples were obtained from 171 IBS patients and 98 HCs for 16S ribosomal RNA gene sequencing and microbial composition analysis.

Results

Having IBS symptoms was associated with consuming a restrictive diet (27.17% of IBS patients vs 7.65% of HCs; odds ratio, 3.25; 95% CI, 1.66-6.75; P value = .006). IBS participants on an exclusion or restrictive diet reported more severe IBS symptoms (P = .042 and .029, respectively). The composition of the microbiota in IBS patients varied depending on the diet consumed. IBS participants on an exclusion diet had a greater abundance of Lachnospira and a lower abundance of Eubacterium (q value, <.05), and those on a restrictive diet had a lower abundance of Lactobacillus (q value, <.05).

Conclusions

Restrictive diets likely are consumed more by IBS patients than HCs to reduce GI symptom severity. Dietary patterns influence the composition of the fecal microbiota and may explain some of the differences between IBS and HCs.