EFFECT OF A DİETİTİAN-SUPERVİSED LOW-FODMAP DİET VERSUS STANDARD WRİTTEN ADVİCE ON GASTROİNTESTİNAL SYMPTOMS AND INFLAMMATORY BİOMARKERS İN IRRİTABLE BOWEL SYNDROME: A RANDOMİZED CONTROLLED TRİAL

Background:

Irritable Bowel Syndrome (IBS) is the most prevalent functional gastrointestinal (GI) pathology among GI disorders. Various dietary interventions, particularly the low-FODMAP diet, are employed to alleviate IBS symptoms.

Study Population & Design:

This study will include 78 adult patients, aged 18-65, diagnosed with IBS according to Rome IV criteria at the Biruni University Faculty of Medicine Hospital Gastroenterology Outpatient Clinic. Participants will be divided into two parallel groups:

Group 1 (n=39): Will receive dietary intervention solely through physician follow-up (provided with a standard hospital brochure listing prohibited foods).

Group 2 (n=39): Will receive structured, personalized dietary intervention through individualized nutritional counseling by a dietitian.

Duration: The low-FODMAP diet intervention for both groups will last for 8 weeks.

Outcome Measures:

At baseline (week 0) and at the conclusion of the study (week 8), the following assessments will be conducted:

Clinical Scores: IBS Symptom Severity Score (IBS-SSS) and the 15-item Gastrointestinal Symptom Rating Scale (GSRS).

Biomarkers: Hs-CRP and fecal calprotectin levels analyzed from blood and stool samples.

Objective:

The primary objective is to determine the impact of individualized nutritional counseling on GI symptoms and inflammatory biomarkers (hs-CRP, fecal calprotectin) during a low-FODMAP diet. Secondary objectives include evaluating the significance of the dietitian's role and observing how lifestyle factors (sleep and physical activity) influence symptom outcomes alongside nutritional therapy.

Study Overview

• Status: Completed
• Conditions: Irritable Bowel Syndrome (IBS)
• Intervention / Treatment: Behavioral: Low-FODMAP Diet Intervention

Detailed Description

The low-FODMAP diet, developed for the treatment of IBS, is defined as a dietary regimen that restricts fermentable oligosaccharides, disaccharides, monosaccharides, and polyols-which are short-chain carbohydrates with limited or poor absorption.

Study Timeline and Interventions:

First Week: A 31-item "Data Collection Form" covering socio-demographic characteristics, health information, and nutritional habits will be administered.

Daily Monitoring: Daily records of the "Bristol Stool Scale" (BSS) will be maintained throughout the study.

Study Duration: The low-FODMAP diet intervention will be implemented for a total duration of 8 weeks.

Face-to-Face Assessments (Conducted at Baseline and Conclusion):

At the beginning and end of the study, the following assessments will be conducted face-to-face with the participants:

• 24-hour Dietary Recall
• Anthropometric measurements
• Frequency of FODMAP-sourced food consumption over the past month
• 7-item "International Physical Activity Questionnaire - Short Form" (IPAQ-SF)
• 5-item "IBS Symptom Severity Score" (IBS-SSS)
• 15-item "Gastrointestinal Symptom Rating Scale" (GSRS)
• 8-item "Epworth Sleepiness Scale" (ESS)

Laboratory Analysis:

Hs-CRP and fecal calprotectin levels will be analyzed from blood and stool samples collected at baseline and at the conclusion of the study.

• Study Type: Interventional
• Enrollment (Actual): 50
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Turkey (Türkiye)
  • Istanbul
    • Istanbul, Istanbul, Turkey (Türkiye)
      • Biruni University Faculty of Medicine Hospital
    • Istanbul, Istanbul, Turkey (Türkiye)
      • Biruni University

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Adults aged 18-65 years.
• Diagnosed with IBS according to the Rome IV criteria.

Exclusion Criteria:

• Use of antibiotics, NSAIDs, oral contraceptives, or hormone therapy during the study.
• Pregnancy or breastfeeding.
• Diagnosis of celiac disease

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Dietitian group; A dietitian planned the low FODMAP diet for the first group (n=31) through individual dietary counselling.	Behavioral: Low-FODMAP Diet Intervention; This intervention consists of an 8-week low-FODMAP dietary regimen aimed at restricting the intake of short-chain carbohydrates, including fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. The intervention is administered through two distinct protocols to compare delivery methods: one group receives standard hospital care consisting of a brief physician follow-up accompanied by a standard educational brochure listing prohibited foods, while the other group receives structured, individualized nutritional counseling and personalized meal planning led by a professional dietitian.
Active Comparator: Doctor group; The second group (n=19) was given a brochure on the low FODMAP diet, as is routine in the hospital, listing foods prohibited by the gastroenterologist.	Behavioral: Low-FODMAP Diet Intervention; This intervention consists of an 8-week low-FODMAP dietary regimen aimed at restricting the intake of short-chain carbohydrates, including fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. The intervention is administered through two distinct protocols to compare delivery methods: one group receives standard hospital care consisting of a brief physician follow-up accompanied by a standard educational brochure listing prohibited foods, while the other group receives structured, individualized nutritional counseling and personalized meal planning led by a professional dietitian.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
IBS-SSS	Irritable Bowel Syndrome Symptom Severity Score (IBS-SSS). The IBS-SSS consists of 5 questions, each scored from 0 to 100, with a maximum possible total score of 500. It determines the severity of abdominal pain, abdominal pain frequency, abdominal bloating severity, satisfaction with bowel habits, and the impact of the disease on quality of life. Total scores are classified as follows: 75-174 points = mild IBS, 175-299 points = moderate IBS, and greater than or equal to 300 points = severe IBS. Higher scores indicate more severe IBS symptoms.	From enrollment to the end of treatment at 8 weeks
GSRS	Gastrointestinal Symptom Rating Scale (GSRS). The GSRS is a 15-item questionnaire that uses a 5-point Likert scale to assess the severity of gastrointestinal symptoms across 5 subscales: abdominal pain, reflux, diarrhoea, indigestion, and constipation. Scores are aggregated to determine symptom severity, where higher scores represent a higher severity of gastrointestinal symptoms.	From enrollment to the end of treatment at 8 weeks
Fecal Calprotectin	Fecal calprotectin levels will be analyzed from stool samples collected from participants to evaluate gastrointestinal inflammation.	From enrollment to the end of treatment at 8 weeks
Hs-CRP	High-Sensitivity C-Reactive Protein (hs-CRP). Hs-CRP levels will be analyzed from blood samples collected from individuals to monitor systemic biochemical findings of inflammation.	From enrollment to the end of treatment at 8 weeks

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Anthropometric measurement data	height in cm, body weight in kg, waist circumference in cm, hip circumference in cm, body composition and bioelectrical impedance analysis (BIA) measurements	From enrollment to the end of treatment at 8 weeks
IPAQ-SF	The IPAQ-SF is a seven-item measure that assesses individuals' physical activity levels over the past seven days. The scale inquires about walking, moderate and vigorous physical activities, and time spent sitting, and physical activity level is calculated in MET-minutes per week	From enrollment to the end of treatment at 8 weeks
Epworth Sleepiness Scale (ESS)	The ESS is an eight-item self-report measure that assesses an individual's likelihood of falling asleep in various everyday situations	From enrollment to the end of treatment at 8 weeks
Data Collection Form	At the beginning of the study, a 31-item Data Collection Form; covering the sociodemographic characteristics, health information and dietary habits of participating patients was administered.	At the beginning of the study
Daily Total FODMAP Intake	Food consumption records were taken for 3 days before and after the diet. The data was entered into the Bebis program. Food consumption records were calculated using the Nutrition Information System (BeBiS, version 9, Germany) for energy, macronutrients, micronutrients and FODMAP amounts (total FODMAP (g) = lactose (g) + oligosaccharides (g) + mannitol (g) + sorbitol (g)). Free fructose, a monosaccharide, could not be included in this programme as it could not be calculated.	From enrollment to the end of treatment at 8 weeks

Collaborators and Investigators

• Sponsor: Biruni University
• Investigators: Study Chair: Sevde KAHRAMAN, Asst. Prof., Biruni University; Study Director: Zeynep Çavdar, Master's student and dietitan, Biruni University; Principal Investigator: Koray Koçhan, Specialist of Gastroenterology, Department of Gastroenterology, Biruni University Faculty of Medicine Hospital; Principal Investigator: Huri Demirci, PhD, Associate Professor, Biruni University; Study Chair: Fatma Çelik, PhD, Professor, Biruni University

Study record dates

Study Major Dates

• Study Start (Actual): April 1, 2025
• Primary Completion (Actual): October 1, 2025
• Study Completion (Actual): October 30, 2025

Study Registration Dates

• First Submitted: May 26, 2026
• First Submitted That Met QC Criteria: May 26, 2026
• First Posted (Actual): June 2, 2026

Study Record Updates

• Last Update Posted (Actual): June 2, 2026
• Last Update Submitted That Met QC Criteria: May 26, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: Irritable Bowel Syndrome (IBS); dietitian; gastrointestinal symptoms; low-FODMAP diet
• Additional Relevant MeSH Terms: Intestinal Diseases; Digestive System Diseases; Gastrointestinal Diseases; Colonic Diseases; Colonic Diseases, Functional; Irritable Bowel Syndrome
• Other Study ID Numbers: 2015-KAEK-80-23-49/SKLOWFODMAP

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No