Gastrointestinal Transit TimeGITTPopNCT07309250
A Study on Gastrointestinal Transit Time at the Population Level
An observational study of Gastrointestinal Transit Time, run by KU Leuven at 1 site in Belgium.
Trial summary
The goal of this study is to investigate the baseline of gastrointestinal transit time (GITT) and explore its relationship with other health indicators in 932 healthy adult volunteers. Read more about this study
- Who is it for?
- Ages 18 to 65 yearsHealthy volunteers can take part
- Conditions the study is for
- Gastrointestinal Transit Time
- What is being tested?
- Diet
- How many people
- 932 participants
- Where
- 1 siteBelgium
- Study dates
- 1 Dec 2025to 30 Dec 2026
- How long will I take part?
- 5 Days
- Phase
- Observational
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 65 years
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Study population: Healthy volunteers from the Flanders region who volunteered to participate in the research
Who may be able to join
- 18-65 years old
- 18.5 kg/m² ≤ BMI ≤ 25 kg/m² or BMI ≥ 30 kg/m² (people with normal weight or obesity)
- Provision of informed consent to participate.
Who cannot join
- Gastrointestinal conditions which may affect nutrient absorption or gastric emptying, including coeliac disease, Crohn's disease, previous resection of the small intestine other than bariatric surgery, gastroparesis;
- Using medications which effect gastric motility (e.g., domperidone, erythromycin, metoclopramide, prucalopride, opiates, loperamide, …)
- The ingredients of blue muffins include gluten, nuts, baking powder, sugar, vanilla extract and sunflower oil. Participants with allergies to these ingredients;
- Current diagnosis of cancer;
- Advanced organ failure, including chronic kidney disease Stage 5, liver cirrhosis Child-Pugh B or C, intestinal failure, heart failure stage D, or chronic obstructive pulmonary disease stage 4;
- Immobility;
- Neuromuscular degenerative conditions associated with muscular atrophy, such as myasthenia gravis, muscular dystrophies, fibromyalgia, or multiple Sclerosis;
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
Belgium1 site, 1 recruiting
- Recruiting
Department of Chronic Diseases and Metabolism
Leuven, Flemish Brabant, 3000
Wim Janssens, +32 016252111, wim.janssens@kuleuven.be
Evelyne van Etten, +32 016330855, evelyne.vanetten@kuleuven.be
About this study
Official title: Gastrointestinal Transit Time at the Population Level: A Cross-sectional Study
The goal of this study is to investigate the baseline of gastrointestinal transit time (GITT) and explore its relationship with other health indicators in 932 healthy adult volunteers.
The main questions it aims to answer are:
Read more
What are the population-level baseline values for GITT using the blue dye method? How is GITT associated with key physiological parameters including blood metabolic markers, life style, and stool characteristics?
Participants will:
Consume a standardized blue dye muffin after overnight fasting at the research center; Offer a finger prock blood samples for metabolic profiling; Collect stool samples for moisture measurement; Complete detailed questionnaires on diet, lifestyle, and bowel habits; Record the time of first blue stool appearance to determine GITT.
Read the detailed description
This explorative study is designed as a cross-sectional investigation aimed at establishing population-level reference values for gastrointestinal transit time (GITT). Adult participants from the general population will undergo GITT measurement using the blue-dye method. This muffin contains blue colorant that cannot be absorbed; after ingestion, it passes through the entire gastrointestinal tract and is eventually excreted in feces. Following a two-day lifestyle standardization period (including dietary and activity guidance) to minimize potential confounding effects on gastrointestinal motility, participants will attend a clinical visit where they will ingest a blue muffin. GITT will be determined by measuring both the time interval between ingestion of the blue muffin and the first appearance of blue-colored stool, and the duration from its first appearance to its complete disappearance.
The blue muffin method has been well-established in previous research for GITT assessment. Building upon the methodology developed by Berry et al., we will introduce stricter pre-test condition controls (includes dietary advice and lifestyle recommendations) and optimized the blue muffin formulation.These improvements allow for reliable measurement with a single muffin administration, which has been evaluated through KU Leuven Health Pass in a large sample size(S-70168).
To investigate potential determinants and correlates of GITT, we will collect biochemical parameters, fecal moisture, and resting metabolic rate. Additionally, participants will complete 24-h diet record and health questionnaires assessing bowel movement, physical activity habits, stress levels, sleep quality and hydration condition for subsequent correlation analyses.
- Conditions
- Gastrointestinal Transit Time
- Being tested
- Diet
- Keywords
- Gastrointestinal motility, Baseline study, Reference value
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
DietOther
Participants will consume a regular muffin containing blue dye
| Study group | Role | What they receive |
|---|---|---|
| Adult participants | Healthy adult participants without serious gastrointestinal diseases Receives: Other: Diet |
What is being measured
The primary outcome is the main question the study is designed to answer.
Gastrointestinal transit time
Calculate the transit time by the recorded muffin consuming time, first blue stool appearance time and last blue stool appearance time
Measured: From enrollment to the end of study at 2 weeks
Secondary outcomes (17)
Height (cm)
Measured using a height meter, in centimeters.
Measured: baseline
Weight (kg)
Measuring using a scale, in kg.
Measured: baseline
BMI
weight and height will be combined to report BMI in kg/m^2
Measured: baseline
Blood glucose (mmol/L)
Measure blood glucose by CardioChek Plus in mmol/L
Measured: baseline
Fat mass (kg)
Using Bodystat quadscan 4000 to measure fat mass (kg)
Measured: baseline
Lean body mass(kg)
Using Bodystat quadscan 4000 to measure lean body mass (kg)
Measured: baseline
Fat percentage (%)
Using Bodystat quadscan 4000 to measure fat%
Measured: baseline
Total cholesterol (mmol/L)
Measuring by Mission cholesterol Meter in mmol/L
Measured: baseline
HDL-C (mmol/L)
Measuring by Mission cholesterol Meter in mmol/L
Measured: baseline
LDL-C (mmol/L)
Measuring by Mission cholesterol Meter in mmol/L
Measured: baseline
Triglyceride (mmol/L)
Measuring by Mission Cholesterol Meter in mmol/L
Measured: baseline
Food record
Participants record their 24-h diets through smartphone application
Measured: 2 days after study
Stool form
Stool form will be evaluated by Bristol Stool Form Scale, the score is from 1 to 7, with values closer to the middle indicating more ideal stool shape.
Measured: baseline
Hydration status
Hydration status will be rated from 1 to 8 by Urine color chart, with higher numbers indicating that the body needs more water.
Measured: baseline
Perceived level of stress
The10-item Perceived Stress will be used to measures an individual's perceived level of stress over the past month. The total score ranges from 0 to 40. A higher score indicates a greater perceived level of stress.
Measured: baseline
Sleep quality
Pittsburgh Sleep Quality Index will be used to assess subjective sleep quality over the past month. The total score ranges from 0 to 21. A higher score indicates poorer sleep quality.
Measured: baseline
Activity level
The Baecke Physical Activity Questionnaire will be used to assess daily habitual physical activity, with a particular focus on work-related and exercise-related activities. It does not produce a single total score, but rather scores on three dimensions, each typically ranging from 1 to 5. On each dimension, a higher score indicates a higher level of physical activity in that area. Therefore, for assessing activity levels, a higher score is generally better.
Measured: baseline
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted30 Dec 2025
- Study start1 Dec 2025
- Primary completion30 Dec 2026 (estimated)
- Study completion30 Dec 2026 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Gastrointestinal Transit TimeStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Observational
- Observational model
- Cohort
- Time perspective
- Cross-sectional
- Enrolment
- 932 participants (estimated)
- Target duration
- 5 Days
Sponsor and investigators
- Lead sponsor
- KU Leuven
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Christophe Matthys, KU Leuven
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07309250
- Sponsor's protocol ID
- S70908
- Acronym
- GITTPop
- Status last verified
- Oct 2026
- First submitted
- 17 Nov 2025
- Last updated
- 6 Oct 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 6 Oct 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Gastrointestinal Transit Time at the Population Level: A Cross-sectional Study
- ClinicalTrials.gov ID
- NCT07309250
- Acronym / sponsor ID
- GITTPop / S70908
- Conditions
- Gastrointestinal Transit Time
- Keywords
- Gastrointestinal motility, Baseline study, Reference value
- Study type
- Observational
- Recruitment status
- Recruiting
- Enrolment
- 932 participants (estimated)
- Lead sponsor
- KU LeuvenUniversity, hospital or other
- Study start
- 1 Dec 2025 (actual)
- Primary completion
- 30 Dec 2026 (estimated)
- Study completion
- 30 Dec 2026 (estimated)
- First posted
- 30 Dec 2025 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
The goal of this study is to investigate the baseline of gastrointestinal transit time (GITT) and explore its relationship with other health indicators in 932 healthy adult volunteers.
The main questions it aims to answer are:
What are the population-level baseline values for GITT using the blue dye method? How is GITT associated with key physiological parameters including blood metabolic markers, life style, and stool characteristics?
Participants will:
Consume a standardized blue dye muffin after overnight fasting at the research center; Offer a finger prock blood samples for metabolic profiling; Collect stool samples for moisture measurement; Complete detailed questionnaires on diet, lifestyle, and bowel habits; Record the time of first blue stool appearance to determine GITT.
Detailed description
This explorative study is designed as a cross-sectional investigation aimed at establishing population-level reference values for gastrointestinal transit time (GITT). Adult participants from the general population will undergo GITT measurement using the blue-dye method. This muffin contains blue colorant that cannot be absorbed; after ingestion, it passes through the entire gastrointestinal tract and is eventually excreted in feces. Following a two-day lifestyle standardization period (including dietary and activity guidance) to minimize potential confounding effects on gastrointestinal motility, participants will attend a clinical visit where they will ingest a blue muffin. GITT will be determined by measuring both the time interval between ingestion of the blue muffin and the first appearance of blue-colored stool, and the duration from its first appearance to its complete disappearance.
The blue muffin method has been well-established in previous research for GITT assessment. Building upon the methodology developed by Berry et al., we will introduce stricter pre-test condition controls (includes dietary advice and lifestyle recommendations) and optimized the blue muffin formulation.These improvements allow for reliable measurement with a single muffin administration, which has been evaluated through KU Leuven Health Pass in a large sample size(S-70168).
To investigate potential determinants and correlates of GITT, we will collect biochemical parameters, fecal moisture, and resting metabolic rate. Additionally, participants will complete 24-h diet record and health questionnaires assessing bowel movement, physical activity habits, stress levels, sleep quality and hydration condition for subsequent correlation analyses.
Study design
- Observational model
- Cohort
- Time perspective
- Cross-sectional
- Target follow-up
- 5 Days
- Number of arms
- 1
| Arm | Type | Receives |
|---|---|---|
| Adult participants | – | Other: DietHealthy adult participants without serious gastrointestinal diseases |
Who may qualify
- Ages
- 18 to 65 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
- Study population
- Healthy volunteers from the Flanders region who volunteered to participate in the research
Key inclusion criteria (3 listed)
- 18-65 years old
- 18.5 kg/m² ≤ BMI ≤ 25 kg/m² or BMI ≥ 30 kg/m² (people with normal weight or obesity)
- Provision of informed consent to participate.
Key exclusion criteria (7 listed)
- Gastrointestinal conditions which may affect nutrient absorption or gastric emptying, including coeliac disease, Crohn's disease, previous resection of the small intestine other than bariatric surgery, gastroparesis;
- Using medications which effect gastric motility (e.g., domperidone, erythromycin, metoclopramide, prucalopride, opiates, loperamide, …)
- The ingredients of blue muffins include gluten, nuts, baking powder, sugar, vanilla extract and sunflower oil. Participants with allergies to these ingredients;
- Current diagnosis of cancer;
- Advanced organ failure, including chronic kidney disease Stage 5, liver cirrhosis Child-Pugh B or C, intestinal failure, heart failure stage D, or chronic obstructive pulmonary disease stage 4;
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| DietParticipants will consume a regular muffin containing blue dye | Other | Adult participants |
Primary outcome
Gastrointestinal transit time
Time frame: From enrollment to the end of study at 2 weeks
Calculate the transit time by the recorded muffin consuming time, first blue stool appearance time and last blue stool appearance time
17 secondary outcomes
Height (cm)
Time frame: baseline
Weight (kg)
Time frame: baseline
BMI
Time frame: baseline
Blood glucose (mmol/L)
Time frame: baseline
Fat mass (kg)
Time frame: baseline
Lean body mass(kg)
Time frame: baseline
Fat percentage (%)
Time frame: baseline
Total cholesterol (mmol/L)
Time frame: baseline
HDL-C (mmol/L)
Time frame: baseline
LDL-C (mmol/L)
Time frame: baseline
Triglyceride (mmol/L)
Time frame: baseline
Food record
Time frame: 2 days after study
Stool form
Time frame: baseline
Hydration status
Time frame: baseline
Perceived level of stress
Time frame: baseline
Sleep quality
Time frame: baseline
Activity level
Time frame: baseline
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 6 Oct 2026.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
An observational study of Gastrointestinal Transit Time, run by KU Leuven at 1 site in Belgium.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 3 inclusion and 7 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 6 Oct 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Belgium. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Christophe Matthys (+32 016342655, christophe.matthys@uzleuven.be), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Gastrointestinal transit time (time frame: From enrollment to the end of study at 2 weeks). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 6 Oct 2026.