Predictors of Symptom-Specific Treatment Response to Dietary Interventions in Irritable Bowel Syndrome

Abstract

(1) Background: Predictors of dietary treatment response in irritable bowel syndrome (IBS) remain understudied. We aimed to investigate predictors of symptom improvement during the low FODMAP and the traditional IBS diet for four weeks. (2) Methods: Baseline measures included faecal Dysbiosis Index, food diaries with daily energy and FODMAP intake, non-gastrointestinal (GI) somatic symptoms, GI-specific anxiety, and psychological distress. Outcomes were bloating, constipation, diarrhea, and pain symptom scores treated as continuous variables in linear mixed models. (3) Results: We included 33 and 34 patients on the low FODMAP and traditional IBS diet, respectively. Less severe dysbiosis and higher energy intake predicted better pain response to both diets. Less severe dysbiosis also predicted better constipation response to both diets. More severe psychological distress predicted worse bloating response to both diets. For the different outcomes, several differential predictors were identified, indicating that baseline factors could predict better improvement in one treatment arm, but worse improvement in the other treatment arm. (4) Conclusions: Psychological, nutritional, and microbial factors predict symptom improvement when following the low FODMAP and traditional IBS diet. Findings may help individualize dietary treatment in IBS.

Keywords: NICE guidelines; diet; disorders of the gut brain interaction; dysbiosis; functional gastrointestinal disorders; gastrointestinal symptoms; irritable bowel syndrome; low FODMAP diet; prediction; treatment response.

Figure 1

Flow chart indicating the number of patients included in each study phase, for details see text. Fermentable oligo-, di-, monosaccharides, and polyols, FODMAP; Patient Health Questionnaire-12, PHQ-12; Visceral Sensitivity Index, VSI; Gastrointestinal Symptom Rating Scale-Irritable Bowel Syndrome, GSRS-IBS.

Figure 2

Predictors of pain improvement during the low FODMAP and traditional IBS diet. (a) Higher energy intake predicted better response to both diets. (b) Lower Dysbiosis Index scores predicted better response to both diets. (c) Oligosaccharide intake was a differential predictor with a non-significant association between higher baseline oligosaccharide intake and a worse response in low FODMAP treatment arm and (d) a significant association between higher baseline oligosaccharide intake and a better response in traditional IBS treatment arm. The GSRS-IBS subscales used in the linear mixed (i.e., random-effect) models were BoxCox transformed. For the transformation of the pain subscale, the following BoxCox formula was used: $y(\lambda )=\frac{y^{\lambda }-1}{\lambda }$. This led to changes in the original score range score of 1–7 to 0–6, using the formula: $y\left(1\right)=\frac{y^1-1}{1}$.

Figure 3

Predictors of constipation improvement during the low FODMAP and traditional IBS diet. (a) A lower Dysbiosis Index score predicted better response to both diets. (b) Disaccharide intake was a differential predictor with a non-significant association between higher baseline disaccharide intake and a worse response in low FODMAP treatment arm and (c) a significant association between higher baseline disaccharide intake and a better response in traditional IBS treatment arm. The GSRS-IBS subscales used in the linear mixed (i.e., random-effect) models were BoxCox transformed. For the transformation of the constipation subscale, the following BoxCox formula was used: $y(\lambda )=\frac{y^{\lambda }-1}{\lambda }$. This led to changes in the original score range score of 1–7 to 0–3.29, using the formula: $y\left(0.5\right)=\frac{y^{0.5}-1}{0.5}$.

Figure 4

Predictors of bloating improvement during the low FODMAP and traditional IBS diet. (a) Higher psychological distress predicted worse response to both diets. (b) Oligosaccharide intake was a differential predictor with a significant association between higher baseline oligosaccharide intake and a worse response in low FODMAP treatment arm and (c) a non-significant association between higher baseline oligosaccharide intake and a better response in traditional IBS treatment arm. The GSRS-IBS subscales used in the linear mixed (i.e., random-effect) models were BoxCox transformed. For the transformation of the bloating subscale, the following BoxCox formula was used: $y(\lambda )=\frac{y^{\lambda }-1}{\lambda }$. This led to changes in the original score range score of 1–7 to 0–6, using the formula: $y\left(1\right)=\frac{y^1-1}{1}$.