Evaluation of the Effects of Gluten Free Diet on Clinical Symptoms and Glycemic Index in Type 2 Diabetic Patients With Non-celiac Gluten Sensitivity

August 3, 2026 updated by: Dr Azita Hekmatdoost, National Nutrition and Food Technology Institute

Confirmed cases of type 2 diabetes who have presented with gastrointestinal symptoms and have no diagnosed gastrointestinal diseases will be referred to the laboratory for testing of tTG IgA and total IgA antibodies to rule out celiac disease, as well as IgE antibody testing to exclude wheat allergy. After ruling out celiac disease, wheat allergy, and irritable bowel syndrome (IBS) using the Rome IV criteria, the patients will be invited to the clinic. The study's objectives, methods, and procedures will be explained, and written informed consent will be obtained from patients who are willing to participate.

At the start of the study, each patient's weight will be measured while wearing light clothing using a mechanical scale (with an accuracy of 100 grams), and height will be measured without shoes using a wall-mounted meter (with an accuracy of 0.5 cm). The body mass index (BMI) of the patients will then be calculated. Additionally, general patient information will be recorded on the data collection form, and the gastrointestinal symptoms questionnaire (NCGS-SQ) will be completed.

Next, blood sample will be drawn from the patients after fasting for 8 to 12 hours, and their serum will be collected to measure glycemic indices, including FBS, HbA1c, insulin, and HOMA-IR. A gluten-free diet (GFD) will be designed by a nutritionist to maintain the weight of type 2 diabetic patients and must be followed for 6 weeks. Carbohydrate distribution and diabetes-related recommendations will also be provided for the patients.

Patient follow-up will be conducted via phone calls to ensure adherence to the diet and to prevent sample loss. Diet compliance will be assessed by a nutritionist, who will review the intake of any gluten-containing foods.

After six weeks (Phase 1), glycemic indices will be re-evaluated through blood tests. Patients who have adhered to the diet optimally and experienced significant improvement in gastrointestinal symptoms will be suspected of having NCGS. If they agree, they will remain in the study and participate in a double-blind, placebo-controlled randomized trial. Those who do not show improvement in gastrointestinal symptoms during the first six weeks will be excluded from the study.

In Phase 2, both the patients and the researchers assessing them will be blinded to the treatment being studied. Intervention group (gluten group) will receive 1 grams of gluten, and control group (placebo group) will receive 1 grams of corn starch powder, to be consumed daily. Patients in both groups will continue following their gluten-free diets. At the end of study , glycemic indices will be re-evaluated, and changes in those indices over the 6-week period will be assessed. Additionally, a clinical symptoms questionnaire will be completed via phone calls every three weeks.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Actual)

40

Phase

  • Not Applicable

Contacts and Locations

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

Study Locations

  • Iran
      • Tehran, Iran, 19437
        • Behboud Clinic

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

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Exclusion of Celiac Disease and Wheat Allergy (tTG IgA antibody test for celiac disease exclusion and IgE antibody test for ruling out wheat allergy)
  • Exclusion of Irritable Bowel Syndrome (IBS) using the Rome IV diagnostic criteria by a gastroenterologist
  • No adherence to any specific diet in the past 6 months, including the gluten-free diet (GFD)
  • Willing and capable of following a gluten-free diet (GFD)
  • No consumption of alcohol or drugs
  • No use of corticosteroids or antidepressant medications
  • No history of thyroid disorders, autoimmune diseases, cancer, or gastrointestinal diseases

Exclusion Criteria:

  • Inability or unwillingness to continue with the study
  • Pregnancy or Lactation
  • Occurrence of any side effects

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

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Triple

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Active Comparator: Intervention
1 gram of gluten powder taken daily
Other: gluten
The intervention group will receive 1 gram of gluten powder daily
Placebo Comparator: Control
1 gram of corn starch powder taken daily
Other: cornstarch
The control group will receive 1 gram of cornstarch powder daily

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Glycated Hemoglobin (HbA1c)
Time Frame: Initially, week 6, and week 12
HbA1C change from baseline
Initially, week 6, and week 12
Fasting Blood Sugar (FBS)
Time Frame: Initially, week 6, and week 12
Blood sugar change from baseline
Initially, week 6, and week 12
Insulin
Time Frame: Initially, week 6, and week 12
blood insulin change from baseline
Initially, week 6, and week 12
Clinical symptoms
Time Frame: Initially, week 3, week 6, week 9, and week 12
changes in GI clinical symptoms from baseline according to visual analogue score of 0-10
Initially, week 3, week 6, week 9, and week 12

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
HOMA-IR
Time Frame: Initially, Week 6, and Week 12
HOMA-IR change from the baseline
Initially, Week 6, and Week 12
Abdominal pain or discomfort
Time Frame: Initially, Week 3, Week 6, Week 9, and Week 12
changes in abdominal pain from baseline according to visual analogue score of 0-10
Initially, Week 3, Week 6, Week 9, and Week 12
Heartburn
Time Frame: Initially, Week 3, Week 6, Week 9, and Week 12
changes in heart burn symptom from baseline according to visual analogue score of 0-10
Initially, Week 3, Week 6, Week 9, and Week 12
Acid reflux
Time Frame: Initially, Week 3, Week 6, Week 9, and Week 12
changes in sense of acid reflux from baseline according to visual analogue score of 0-10
Initially, Week 3, Week 6, Week 9, and Week 12
Nausea and vomiting
Time Frame: Initially, Week 3, Week 6, Week 9, and Week 12
changes in nausea and vomiting symptoms from baseline according to visual analogue score of 0-10
Initially, Week 3, Week 6, Week 9, and Week 12
Bloating
Time Frame: Initially, Week 3, Week 6, Week 9, and Week 12
changes in bloating sense from baseline according to visual analogue score of 0-10
Initially, Week 3, Week 6, Week 9, and Week 12
Borborygmus (stomach rumbling)
Time Frame: Initially, Week 3, Week 6, Week 9, and Week 12
changes in Borborygmus symptoms from baseline according to visual analogue score of 0-10
Initially, Week 3, Week 6, Week 9, and Week 12
Abdominal distension
Time Frame: Initially, Week 3, Week 6, Week 9, and Week 12
changes in abdominal distension symptoms from baseline according to visual analogue score of 0-10
Initially, Week 3, Week 6, Week 9, and Week 12
Feeling of belching (burping)
Time Frame: Initially, Week 3, Week 6, Week 9, and Week 12
changes in feeling of belching from baseline according to visual analogue score of 0-10
Initially, Week 3, Week 6, Week 9, and Week 12
flatulence
Time Frame: Initially, Week 3, Week 6, Week 9, and Week 12
changes in flatulence symptom from baseline according to visual analogue score of 0-10
Initially, Week 3, Week 6, Week 9, and Week 12
Reduced stool passage
Time Frame: Initially, Week 3, Week 6, Week 9, and Week 12
changes in feeling reduced stool passage from baseline according to visual analogue score of 0-10
Initially, Week 3, Week 6, Week 9, and Week 12
Increased stool passage
Time Frame: Initially, Week 3, Week 6, Week 9, and Week 12
changes in feeling increased stool passage from baseline according to visual analogue score of 0-10
Initially, Week 3, Week 6, Week 9, and Week 12
Loose stools
Time Frame: Initially, Week 3, Week 6, Week 9, and Week 12
changes in number of loose stools per day from baseline according to visual analogue score of 0-10
Initially, Week 3, Week 6, Week 9, and Week 12
Hard stools
Time Frame: Initially, Week 3, Week 6, Week 9, and Week 12
changes in hard stools per day from baseline according to visual analogue score of 0-10
Initially, Week 3, Week 6, Week 9, and Week 12
Urgency to defecate
Time Frame: Initially, Week 3, Week 6, Week 9, and Week 12
changes in frequency of urgency to defecate from baseline according to visual analogue score of 0-10
Initially, Week 3, Week 6, Week 9, and Week 12
Feeling of incomplete evacuation
Time Frame: Initially, Week 3, Week 6, Week 9, and Week 12
changes in feeling of incomplete evacuation from baseline according to visual analogue score of 0-10
Initially, Week 3, Week 6, Week 9, and Week 12
Extraintestinal symptoms
Time Frame: Initially, Week 3, Week 6, Week 9, and Week 12
changes in extra-intestinal symptoms from baseline according to visual analogue score of 0-10
Initially, Week 3, Week 6, Week 9, and Week 12

Collaborators and Investigators

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

Sponsor

National Nutrition and Food Technology Institute

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)

March 1, 2025

Primary Completion (Actual)

April 1, 2026

Study Completion (Actual)

August 1, 2026

Study Registration Dates

First Submitted

March 17, 2025

First Submitted That Met QC Criteria

March 22, 2025

First Posted (Actual)

March 28, 2025

Study Record Updates

Last Update Posted (Actual)

August 6, 2026

Last Update Submitted That Met QC Criteria

August 3, 2026

Last Verified

August 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 43012148

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

UNDECIDED

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

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.

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