How sourdough bread compared with white bread affects blood sugar, digestion and appetite in adults
| ISRCTN | ISRCTN11866792 |
|---|---|
| DOI | https://doi.org/10.1186/ISRCTN11866792 |
| Sponsor | University College Dublin |
| Funders | Enterprise Ireland, Aryzta Bakeries Ireland |
- Submission date
- 18/03/2026
- Registration date
- 19/03/2026
- Last edited
- 18/03/2026
- Recruitment status
- Recruiting
- Overall study status
- Ongoing
- Condition category
- Nutritional, Metabolic, Endocrine
Plain English summary of protocol
Background and study aims
Sourdough bread is often perceived as a healthier alternative to standard white bread, but evidence is mixed and the reasons for any differences are not fully understood. This study aims to compare sourdough bread and white or yeast bread and measure how they affect blood sugar levels after a meal, as well as feelings of hunger and fullness, in adults.
Who can participate?
Adults aged 20-45 years. Participants will be eligible for one of two cohorts: (1) metabolically healthy adults or (2) adults with two or more symptoms of the metabolic syndrome (such as raised blood pressure, raised blood glucose, or body mass index (BMI) ≥30 kg/m²).
What does the study involve?
Each participant will attend two full-day (8-hour) study visits, separated by at least 7 days. On each visit, participants will consume a bread-based breakfast test meal (either sourdough bread or white/yeast bread, with the order assigned at random). Blood sugar will be monitored using a small wearable glucose sensor. Participants will also complete short questionnaires about appetite (hunger/fullness) during the visit. Standardised refreshments or meals may be provided as part of the visit schedule.
What are the possible benefits and risks of participating?
Participants may learn how their blood sugar responds to different bread products, but there may be no direct health benefit. Risks are minimal and may include mild skin irritation or discomfort from wearing the glucose sensor and typical minor inconvenience associated with attending two long study visits and following the study instructions (e.g., fasting before visits).
Where is the study run from?
University College Dublin (UCD) (Ireland)
When is the study starting and how long is it expected to run for?
March 2026 to September 2026
Who is funding the study?
This study is supported through the Enterprise Ireland Innovation Partnership Programme, in collaboration with Aryzta Bakeries Ireland, with UCD as the lead academic partner and Teagasc as a partner institution.
Who is the main contact?
Dr Emma Feeney, emma.feeney@ucd.ie
Contact information
Principal investigator, Public, Scientific
School of Agriculture and Food Science, University College Dublin, Belfield
Dublin
D04 V1W8
Ireland
| Phone | +353 (0)17162247 |
|---|---|
| emma.feeney@ucd.ie |
Study information
| Primary study design | Interventional |
|---|---|
| Allocation | Randomized controlled trial |
| Masking | Open (masking not used) |
| Control | Active |
| Assignment | Crossover |
| Purpose | Prevention |
| Scientific title | The acute glycaemic, digestive and appetite response to sourdough bread versus white bread: a randomised crossover trial |
| Study objectives | |
| Ethics approval(s) |
Approved 10/02/2026, UCD Human Research Ethics Committee - Sciences (UCD Office of Research Ethics, UCD Research Building, University College Dublin, Belfield, Dublin, D04 V1W8, Ireland; +353 (0) 1 716 7777; research.ethics@ucd.ie), ref: LS-25-70-Feeney-2 |
| Health condition(s) or problem(s) studied | Postprandial glycaemic response and metabolic health in adults with and without increased metabolic risk |
| Intervention | This is a randomised, controlled, crossover study comparing two bread interventions: sourdough bread (intervention) and white/yeast bread (control). Participants will be randomised to the order in which they receive each bread type using a randomised crossover design. Each participant will attend two full-day study visits (approximately 8 hours each) at the UCD Institute of Food and Health, separated by a washout period of at least 7 days. On each visit, participants will consume a standardised bread-based breakfast test meal containing either sourdough bread or white/yeast bread, as assigned by randomisation. The quantity of bread provided will be standardised across both visits. A standardised lunch will also be provided during each visit. Blood glucose will be monitored continuously throughout each visit using a wearable continuous glucose monitor (CGM). Appetite and satiety will be assessed at regular intervals using a Visual Analogue Scale (VAS) questionnaire measuring hunger, fullness, thirst, desire to eat, and prospective food consumption. Participants will be required to fast prior to each visit in accordance with study instructions. |
| Intervention type | Behavioural |
| Primary outcome measure(s) |
|
| Key secondary outcome measure(s) | |
| Completion date | 30/09/2026 |
Eligibility
| Participant type(s) | |
|---|---|
| Age group | Adult |
| Lower age limit | 20 Years |
| Upper age limit | 45 Years |
| Sex | All |
| Target sample size at registration | 30 |
| Key inclusion criteria | 1. Adults aged 20–45 years 2. Eligible for one of two cohorts: 2.1. Metabolically healthy adults, or 2.2. Adults with body mass index ≥30 kg/m² (metabolic health risk cohort) 3. Willing and able to attend two full-day (8-hour) study visits separated by ≥7 days 4. Willing to consume the provided bread test meals and to wear a glucose sensor for blood glucose monitoring 5. Able to provide written informed consent |
| Key exclusion criteria | 1. Diagnosed diabetes or other clinically significant metabolic disease 2. Use of medication known to affect glucose metabolism (e.g., glucose-lowering drugs, systemic corticosteroids) 3. Coeliac disease or wheat/gluten allergy/intolerance, or other food allergy relevant to the test breads 4. Gastrointestinal disease or major gastrointestinal surgery (excluding uncomplicated appendectomy) 5. Pregnancy or breastfeeding 6. Current smoker or high alcohol intake (as defined by the study team) 7. Acute illness at the time of study visits 8. Any condition that, in the investigator’s opinion, makes participation unsafe or affects study outcomes |
| Date of first enrolment | 15/03/2026 |
| Date of final enrolment | 31/07/2026 |
Locations
Countries of recruitment
- Ireland
Study participating centres
Results and Publications
| Individual participant data (IPD) Intention to share | No |
|---|---|
| IPD sharing plan |
Editorial Notes
18/03/2026: Study's existence confirmed by the UCD Human Research Ethics Committee - Sciences.
