Impact of Mediterranean Diet and Processed Food Consumption on Gastrointestinal Symptoms in Coeliac Patients on a Gluten-Free Diet

October 28, 2026 updated by: Istituti Clinici Scientifici Maugeri SpA

MEDITERRANEAN DIET, HIGHLY PROCESSED FOODS AND THEIR IMPACT ON GASTROINTESTINAL SYMPTOMS, NUTRITIONAL STATUS AND QUALITY OF LIFE IN ADULT COELIAC DISEASE PATIENTS ON A GLUTEN FREE DIET: A MULTICENTRE CROSS-SECTIONAL STUDY

Coeliac disease is a lifelong autoimmune condition in which the immune system reacts to gluten, a protein found in wheat, barley and rye, affecting about 1% of the general population. The only currently approved treatment is a strict, lifelong gluten-free diet (GFD). Although strict adherence to a gluten-free diet leads to mucosal recovery in most patients, up to 20-30% of coeliac patients continue to experience persistent gastrointestinal symptoms (such as abdominal pain, bloating, diarrhoea or constipation). Furthermore, commercially prepared gluten-free products often contain higher amounts of fat, sugar and salt, and lower amounts of fibre, protein, folate and vitamins compared with gluten-containing equivalents.

Conversely, the Mediterranean diet-rich in vegetables, fruits, legumes, fish, nuts and extra-virgin olive oil-is widely recognised for its benefits on cardiovascular, metabolic and gut health, as well as quality of life, in contrast to diets rich in highly or ultra-processed foods.

This multicentre cross-sectional observational study aims to evaluate whether adult coeliac patients on a long-term strict gluten-free diet whose habitual diet more closely aligns with the Mediterranean dietary pattern are less likely to experience persistent gastrointestinal symptoms and have a better quality of life and nutritional status, and conversely whether higher consumption of highly processed foods is associated with worse symptoms, poorer quality of life and less adequate nutritional status. No dietary intervention is provided as part of the study; participants complete validated questionnaires and undergo routine anthropometric and blood assessments during a single regular outpatient follow-up visit.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Detailed Description

This is a multicentre, observational, cross-sectional, no-profit study promoted and coordinated by ICS Maugeri SpA IRCCS di Pavia (Protocol Code: CTSPV40-24).

Objectives:

  • Primary Objective: To evaluate the relationship between adherence to a Mediterranean diet and gastrointestinal symptoms, coeliac disease-related quality of life, and nutritional status in a population of adult coeliac patients on a strict gluten-free diet (GFD) regularly followed at participating gastroenterology outpatient clinics.
  • Secondary Objective: To evaluate whether coeliac patients who consume higher amounts of highly processed (ultra-processed) foods have more persistent gastrointestinal symptoms, a worse quality of life, and a less adequate nutritional status.

Study Procedures and Observational Nature:

Patients attending routine gastroenterology outpatient follow-up visits will be invited to participate. All enrolled patients must have been on a strict GFD for at least 12 months with histological evidence of duodenal mucosal recovery on a follow-up biopsy. As clarified with the Ethics Committee (CET Lombardia 6), no specific Mediterranean diet is prescribed or provided within this study: all patients were instructed on how to follow a strict GFD at the time of coeliac disease diagnosis by expert physicians or dietitians as part of standard clinical practice, completely independently of this study. During a single study visit (with no scheduled study follow-up), the degree of adherence to the Mediterranean diet, consumption of highly processed foods, GFD compliance, gastrointestinal symptoms, and quality of life are assessed using standardized, validated questionnaires:

  1. PyrMDS: 15-item Pyramid-based Mediterranean Diet Score (score range 0-15).
  2. sQ-HPF: Short screening Questionnaire of Highly Processed Food consumption (score range 0-14 and % HPF).
  3. Biagi GFD Score: Gluten-free diet adherence score (score range 0-4).
  4. GSRS-CD (CeD-GSRS): Gastrointestinal Symptom Rating Scale including the 10 items on the Celiac Disease domains (7-point Likert scale per item).
  5. CDQ (CD-QOL): Celiac Disease-specific Quality of Life scale, Italian validated version (20 items on a 5-point Likert scale).

Nutritional status is evaluated through standard anthropometric measurements (height, weight, BMI, waist circumference) and routine clinical practice biochemical blood tests (hemoglobin, ferritin, folate, vitamin B12, vitamin D, calcium, albumin, ALT, AST, GGT, total cholesterol, LDL cholesterol, HDL cholesterol, triglycerides, and fasting glucose).

Sample Size and Statistical Plan:

A minimum of 300 adult coeliac patients will be enrolled across 10 Italian centres over approximately 12-18 months (providing ~75% power to detect a small-to-medium effect size of Cohen's d = 0.3 at alpha = 0.05, and >80% power for Cohen's d = 0.5, while supporting multivariable regression models). Descriptive statistics, independent samples t-tests or Mann-Whitney U tests, Chi-square or Fisher's exact tests, Pearson's or Spearman's correlation coefficients, multiple linear regression models (for continuous outcomes), and multivariable logistic regression models (for dichotomous outcomes such as presence/absence of persistent gastrointestinal symptoms) will be used, adjusting for potential confounders including age, sex, duration of GFD, and comorbidities. Missing data on key variables will be addressed via multiple imputation with sensitivity analyses. Two-sided p-values < 0.05 will be considered statistically significant.

Study Type

Observational

Enrollment (Estimated)

300

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

Study Locations

    • BS
      • Brescia, BS, Italy, 25123
        • Recruiting
        • ASST Spedali Civili di Brescia, Gastroenterologia
        • Contact:
    • FE
      • Ferrara, FE, Italy, 44121
        • Recruiting
        • Università degli Studi di Ferrara
        • Contact:
    • Michigan
      • Milan, Michigan, Italy, 20122
        • Recruiting
        • Center for Prevention and Diagnosis of Celiac Disease - Gastroenterology and Endoscopy Unit, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico
        • Contact:
    • PD
      • Padua, PD, Italy, 35128
        • Recruiting
        • University of Padua, Department of Surgery, Oncology and Gastroenterology
        • Contact:
    • PV
      • Pavia, PV, Italy, 27100
        • Recruiting
        • Fondazione IRCCS Policlinico San Matteo, SC Medicina Generale
        • Contact:
      • Pavia, PV, Italy, 27100
        • Recruiting
        • ICS Maugeri SpA IRCCS, Gastroenterology Unit
        • Contact:
    • RA
      • Ravenna, RA, Italy, 48121

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

18 years and older (Adult, Older Adult)

Accepts Healthy Volunteers

No

Genders Eligible for Study

All

Sampling Method

Non-Probability Sample

Study Population

Adult patients (age > 18 years) with biopsy-confirmed coeliac disease on a strict gluten-free diet for at least 12 months and with histological evidence of mucosal recovery on follow-up duodenal biopsy, consecutively recruited during routine follow-up visits at 10 participating Italian gastroenterology outpatient clinics.

Description

Inclusion Criteria:

  • Adult patients (age > 18 years)
  • Diagnosis of coeliac disease based on positive IgA tissue transglutaminase / endomysial antibodies and villous atrophy on duodenal biopsy in accordance with major international guidelines
  • Strict adherence to a gluten-free diet (GFD) for at least 12 months
  • Evidence of duodenal mucosal recovery on a follow-up biopsy
  • Regularly attending the participating gastroenterology outpatient clinics for follow-up

Exclusion Criteria:

  • Coeliac patients with poor gluten-free diet adherence and/or evidence of persistent villous atrophy on follow-up duodenal biopsy
  • Patients who follow a vegetarian/vegan diet or other restrictive diets

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Observational Models: OTHER
  • Time Perspectives: CROSS_SECTIONAL

Cohorts and Interventions

Group / Cohort
Intervention / Treatment
Adult Coeliac Disease Patients on a Long-Term Gluten-Free Diet

Adult patients (age > 18 years) with biopsy-proven coeliac disease on a strict gluten-free diet for at least 12 months and with documented duodenal mucosal recovery on follow-up biopsy, attending routine gastroenterology outpatient follow-up visits at the participating centres.

Observational assessment of the degree of adherence to the Mediterranean dietary pattern within the patient's habitual gluten-free diet, measured using the validated 15-item Pyramid-based Mediterranean Diet Score (PyrMDS, continuous score 0 to 15 across 15 food groups: vegetables, legumes, fruits, nuts, cereals, dairy, fish, red meat, processed meat, white meat, eggs, potatoes, sweets, alcohol, and olive oil). No dietary intervention is administered.

Other Names:
  • 15-Items Pyramid-based Mediterranean Diet Score (PyrMDS)

Observational assessment of habitual consumption of highly processed / ultra-processed foods within the patient's gluten-free diet, measured using the validated short screening Questionnaire of Highly Processed Food consumption (sQ-HPF, score range 0 to 14 and estimated % HPF). No dietary intervention is administered.

Other Names:
  • Short Questionnaire of Highly Processed Food consumption (sQ-HPF)
  • Ultra-Processed Foods (UPF) intake

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Celiac Disease Gastrointestinal Symptom Rating Scale (CeD-GSRS) Score
Time Frame: Baseline (Single cross-sectional study visit, Day 1)

Severity of gastrointestinal symptoms over the past week, measured with the 10-item CeD-GSRS. Each item is rated on a 7-point Likert scale (1 = no discomfort at all; 7 = very severe discomfort). The score is the mean of the 10 items, ranging from 1 to 7, and higher scores indicate more severe symptoms. The score will be analysed in relation to Mediterranean diet adherence (PyrMDS) and highly processed food consumption (sQ-HPF), using correlation and multivariable linear regression.

Baseline (Single cross-sectional study visit, Day 1)
Celiac Disease-Specific Quality of Life (CD-QOL) Score
Time Frame: Baseline (Single cross-sectional study visit, Day 1)

Coeliac disease-specific quality of life over the past 30 days, measured with the Italian validated 20-item CD-QOL. Items are rated on a 5-point Likert scale and the total score is transformed to a 0-100 scale, where higher scores indicate better quality of life. The score will be analysed in relation to PyrMDS and sQ-HPF scores, using correlation and multivariable linear regression.

Baseline (Single cross-sectional study visit, Day 1)
Pyramid-based Mediterranean Diet Score (PyrMDS)
Time Frame: Baseline (Single cross-sectional study visit, Day 1)

Adherence to the Mediterranean dietary pattern, measured with the 15-item PyrMDS. The score is continuous and ranges from 0 to 15, where higher scores indicate greater adherence.

Baseline (Single cross-sectional study visit, Day 1)
Body Mass Index (BMI)
Time Frame: Baseline (Single cross-sectional study visit, Day 1)

BMI is calculated from measured weight and height (kg/m²). It will be analysed in relation to PyrMDS and sQ-HPF scores, using correlation and multivariable linear regression.

Baseline (Single cross-sectional study visit, Day 1)

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Short Questionnaire of Highly Processed Food Consumption (sQ-HPF) Score
Time Frame: Baseline (Single cross-sectional study visit, Day 1)

Habitual consumption of highly processed foods, measured with the sQ-HPF. The score ranges from 0 to 14, where higher scores indicate greater consumption.

Baseline (Single cross-sectional study visit, Day 1)
Gluten-Free Diet Adherence (Biagi Score)
Time Frame: Baseline (Single cross-sectional study visit, Day 1)

Adherence to the gluten-free diet, measured with the Biagi score. The score ranges from 0 to 4, where higher scores indicate stricter adherence.

Baseline (Single cross-sectional study visit, Day 1)
Percentage of Participants with Persistent Gastrointestinal Symptoms
Time Frame: Baseline (Single cross-sectional study visit, Day 1)

The proportion of participants with persistent self-reported gastrointestinal symptoms. This proportion will be analysed in relation to PyrMDS and sQ-HPF scores using multivariable logistic regression.

Baseline (Single cross-sectional study visit, Day 1)
Waist Circumference
Time Frame: Baseline (Single cross-sectional study visit, Day 1)

Waist circumference (cm), measured according to standard procedures. It will be analysed in relation to PyrMDS and sQ-HPF scores, using correlation analysis.

Baseline (Single cross-sectional study visit, Day 1)
Total Cholesterol
Time Frame: Baseline (Single cross-sectional study visit, Day 1)

Serum total cholesterol (mg/dL) from routine blood tests. It will be analysed in relation to PyrMDS and sQ-HPF scores, using correlation analysis.

Baseline (Single cross-sectional study visit, Day 1)
LDL Cholesterol
Time Frame: Baseline (Single cross-sectional study visit, Day 1)

Serum LDL cholesterol (mg/dL) from routine blood tests. It will be analysed in relation to PyrMDS and sQ-HPF scores, using correlation analysis.

Baseline (Single cross-sectional study visit, Day 1)
HDL Cholesterol
Time Frame: Baseline (Single cross-sectional study visit, Day 1)

Serum LDL cholesterol (mg/dL) from routine blood tests. It will be analysed in relation to PyrMDS and sQ-HPF scores, using correlation analysis.

Baseline (Single cross-sectional study visit, Day 1)
Triglycerides
Time Frame: Baseline (Single cross-sectional study visit, Day 1)

Serum triglycerides (mg/dL) from routine blood tests. They will be analysed in relation to PyrMDS and sQ-HPF scores, using correlation analysis.

Baseline (Single cross-sectional study visit, Day 1)
Fasting Glucose
Time Frame: Baseline (Single cross-sectional study visit, Day 1)

Fasting plasma glucose (mg/dL) from routine blood tests. It will be analysed in relation to PyrMDS and sQ-HPF scores, using correlation analysis.

Baseline (Single cross-sectional study visit, Day 1)

Other Outcome Measures

Outcome Measure
Measure Description
Time Frame
Hemoglobin
Time Frame: Baseline (Single cross-sectional study visit, Day 1)

Serum hemoglobin concentration (g/dL) from routine blood tests. It will be analysed in relation to PyrMDS and sQ-HPF scores, using correlation analysis.

Baseline (Single cross-sectional study visit, Day 1)
Ferritin
Time Frame: Baseline (Single cross-sectional study visit, Day 1)

Serum ferritin concentration (ng/mL) from routine blood tests. It will be analysed in relation to PyrMDS and sQ-HPF scores, using correlation analysis.

Baseline (Single cross-sectional study visit, Day 1)
Folate
Time Frame: Baseline (Single cross-sectional study visit, Day 1)

Serum folate concentration (ng/mL) from routine blood tests. It will be analysed in relation to PyrMDS and sQ-HPF scores, using correlation analysis.

Baseline (Single cross-sectional study visit, Day 1)
Vitamin B12
Time Frame: Baseline (Single cross-sectional study visit, Day 1)

Serum vitamin B12 concentration (pg/mL) from routine blood tests. It will be analysed in relation to PyrMDS and sQ-HPF scores, using correlation analysis.

Baseline (Single cross-sectional study visit, Day 1)
Vitamin D (25-hydroxyvitamin D)
Time Frame: Baseline (Single cross-sectional study visit, Day 1)

Serum 25-hydroxyvitamin D concentration (ng/mL) from routine blood tests. It will be analysed in relation to PyrMDS and sQ-HPF scores, using correlation analysis.

Baseline (Single cross-sectional study visit, Day 1)
Albumin
Time Frame: Baseline (Single cross-sectional study visit, Day 1)

Serum albumin concentration (g/dL) from routine blood tests. It will be analysed in relation to PyrMDS and sQ-HPF scores, using correlation analysis.

Baseline (Single cross-sectional study visit, Day 1)
Alanine Aminotransferase (ALT)
Time Frame: Baseline (Single cross-sectional study visit, Day 1)

Serum ALT (U/L) from routine blood tests. It will be analysed in relation to PyrMDS and sQ-HPF scores, using correlation analysis.

Baseline (Single cross-sectional study visit, Day 1)
Aspartate Aminotransferase (AST)
Time Frame: Baseline (Single cross-sectional study visit, Day 1)

Serum AST (U/L) from routine blood tests. It will be analysed in relation to PyrMDS and sQ-HPF scores, using correlation analysis.

Baseline (Single cross-sectional study visit, Day 1)
Gamma-Glutamyl Transferase (GGT)
Time Frame: Baseline (Single cross-sectional study visit, Day 1)

Serum GGT (U/L) from routine blood tests. It will be analysed in relation to PyrMDS and sQ-HPF scores, using correlation analysis.

Baseline (Single cross-sectional study visit, Day 1)
Calcium
Time Frame: Baseline (Single cross-sectional study visit, Day 1)

Serum calcium concentration (mg/dL) from routine blood tests. It will be analysed in relation to PyrMDS and sQ-HPF scores, using correlation analysis.

Baseline (Single cross-sectional study visit, Day 1)

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Investigators

  • Principal Investigator: Annalisa Schiepatti, MD, PhD, ICS Maugeri SpA IRCCS

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

July 1, 2025

Primary Completion (Estimated)

December 31, 2026

Study Completion (Estimated)

December 31, 2026

Study Registration Dates

First Submitted

October 23, 2026

First Submitted That Met QC Criteria

October 28, 2026

First Posted (Actual)

November 4, 2026

Study Record Updates

Last Update Posted (Actual)

November 4, 2026

Last Update Submitted That Met QC Criteria

October 28, 2026

Last Verified

October 1, 2026

More Information

Terms related to this study

Other Study ID Numbers

  • CTSPV40-24

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

IPD not shared due to privacy and data protection regulations.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.