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This randomized controlled trial aims to study how a high intake of a fibre-rich bread affects the composition and functioning of the gut microbiota in healthy subjects, and how this, in turn, impacts on the release of gut peptides, intestinal permeability, stress and cognitive performance.
Healthy subjects will be recruited for a 3-week, randomized, parallel-controlled study. Subjects that are eligible to take part in the study will be blinded and randomly allocated to consume a fibre-rich bread or a control bread daily for 3 weeks. Measurements of biomarkers related to the gut-brain axis, microbiota composition and functioning, intestinal permeability, stress and cognitive functioning will be conducted on two separate test days, at baseline and after the 3 weeks intervention. On both test days (day 0 and day 21) subjects will come to the study centre after a 10 hours overnight fast and will deliver faecal samples collected at home. At the study centre, blood samples will be collected and a device for continuous assessment of autonomic nervous system response (Biopac) will be placed. Subjects will drink a multisugar solution and urine samples will be collected for gut permeability analysis. Sugar solution intake will be followed by a baseline period during which participants will rest for 30 minutes to adapt to the laboratory setting. After the baseline period, subjects will conduct a stress test and cognitive tests. Visual analogue scales (VAS) to assess momentary perceived stress levels and saliva samples will be collected before and after the stress test. The study subjects will also complete questionnaires at both visits (food frequency questionnaire, food diary, physical activity, gastrointestinal symptom rating scale, Euro Quality of Life).
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| High-fibre bread | Experimental | Six slices (180 g) of whole grain rye bread divided over the meals during the day for 3 weeks |
|
| Control bread | Placebo Comparator | Six slices (180 g) of control bread containing refined wheat and oat flour divided over the meals during the day for 3 weeks |
|
| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Whole grain bread | Dietary Supplement | Consumption of high-fibre bread as a dietary supplementation |
|
| Measure | Description | Time Frame |
|---|---|---|
| Microbiota composition baseline vs after intervention using 16S RNA gene sequencing | Difference in gut microbiota composition in faecal samples before (baseline) and after intake of six slices of bread for 3 weeks (after intervention) using 16S RNA gene sequencing | faecal samples collected before and after intake of bread for 3 weeks |
| Measure | Description | Time Frame |
|---|---|---|
| Microbiota composition whole grain rye bread vs control bread using 16S RNA gene sequencing | Difference in gut microbiota composition in faecal samples between the study arms using 16S RNA gene sequencing | faecal samples collected before and after intake of bread for 3 weeks |
| Concentrations of circulatory short-chain fatty acids SCFA |
| Measure | Description | Time Frame |
|---|---|---|
| Gastrointestinal symptoms measured by Gastrointestinal Symptom Rating Scale in Irritable Bowel Syndrome (GSRS-IBS) | Difference in the frequency and severity of gastrointestinal symptoms between and within intervention groups after the intake of bread for 3 weeks. The GSRS-IBS contains 13 self-report items rated on a 6-point Likert scale ranging from 1 (no discomfort at all) to 7 (very severe discomfort). Total scores range from 0 to 78. |
Inclusion Criteria:
Exclusion Criteria:
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| Name | Affiliation | Role |
|---|---|---|
| Rebecca Wall, PhD | Örebro University, Sweden | Principal Investigator |
| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Örebro University | Örebro | Sweden |
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double blinding
| Control bread | Dietary Supplement | Consumption of control bread as a dietary supplementation |
|
Difference in blood levels of SCFA between and within intervention groups after intake of bread for 3 weeks |
| blood samples collected before and after intake of bread for 3 weeks |
| Concentrations of faecal SCFA | Difference in faecal levels of SCFA between and within intervention groups after intake of bread for 3 weeks | faecal samples collected before and after intake of bread for 3 weeks |
| Concentrations of blood glucagon like peptide-1 (GLP-1) | Difference in blood levels of GLP-1 between and within intervention groups after intake of bread for 3 weeks | blood samples collected before and after intake of bread for 3 weeks |
| Concentrations of blood glucagon like peptide-2 (GLP-2) | Difference in blood levels of GLP-2 between and within intervention groups after intake of bread for 3 weeks | blood samples collected before and after intake of bread for 3 weeks |
| Concentrations of blood peptide YY (PYY) | Difference in blood levels of PYY between and within intervention groups after intake of bread for 3 weeks | blood samples collected before and after intake of bread for 3 weeks |
| Concentrations of blood gastric inhibitory polypeptide (GIP) | Difference in blood levels of GIP between and within intervention groups after intake of bread for 3 weeks | blood samples collected before and after intake of bread for 3 weeks |
| Concentrations of blood neuroactive peptide Y (NPY) | Difference in blood levels of NPY between and within intervention groups after intake of bread for 3 weeks | blood samples collected before and after intake of bread for 3 weeks |
| Concentrations of blood brain-derived neurotrophic factor (BDNF) | Difference in blood levels of BDNF between and within intervention groups after intake of bread for 3 weeks | blood samples collected before and after intake of bread for 3 weeks |
| Concentrations of blood cytokines | Difference in blood levels of cytokines between and within intervention groups after intake of bread for 3 weeks | blood samples collected before and after intake of bread for 3 weeks |
| Concentrations of blood alkylresorcinols | Difference in blood levels of alkylresorcinols between and within intervention groups after intake of bread for 3 weeks | blood samples collected before and after intake of bread for 3 weeks |
| Concentrations of blood lipopolysaccharide-binding protein (LBP) | Difference in blood levels of LBP between and within intervention groups after intake of bread for 3 weeks | blood samples collected before and after intake of bread for 3 weeks |
| Concentrations of blood soluble CD-14 (sCD-14) | Difference in blood levels of sCD-14 between and within intervention groups after intake of bread for 3 weeks | blood samples collected before and after intake of bread for 3 weeks |
| Concentrations of sugars in urine | Difference on intestinal permeability between and within intervention groups after intake of bread for 3 weeks measured by the excretion of sugars contained in a multi-sugar solution | urine samples collected before and after intake of bread for 3 weeks |
| Concentrations of saliva cortisol during stress test | Difference in saliva levels of cortisol produced during stress test between and within intervention groups after intake of bread for 3 weeks | Saliva samples collected before the stress test, after the introduction phase, directly after the acute stress phase, 5 minutes, 10-15 minutes, 60 minutes, and 75 minutes after the stress test |
| Concentrations of saliva alpha-amylase during stress test | Difference in saliva levels of a-amylase produced during stress test between and within intervention groups after intake of bread for 3 weeks | Saliva samples collected before the stress test, after the introduction phase, directly after the acute stress phase, 5 minutes, 10-15 minutes, 60 minutes, and 75 minutes after the stress test |
| 3 weeks |
| Food habits measured by an electronic food frequency questionnaire Mealq | Survey of participants' food habits before and during the intake of bread for 3 weeks | 3 weeks |
| Food habits measured by a Food diary | Survey of participants' food habits before and during the intake of bread for 3 weeks | 3 days |
| Physical activity measured by the International Physical Activity Questionnaire (IPAQ) | Survey of participants' physical activities before and during the intake of bread for 3 weeks. The IPAQ contains 7 self-report questions and the categorical score is divided into 3 levels: low (less than 600 metabolic equivalent-minutes/week), moderate (at least 600 metabolic equivalent-minutes/week) or high (at least 1500 metabolic equivalent-minutes/week). | 3 days |
| Quality of life measured by the Euro Quality of Life questionnaire | Survey of participants' well-being before and during the intake of bread for 3 weeks. It records the patient's self-rated health on a vertical visual analogue scale where the endpoints are labelled from 0 (worst imaginable health state) to 100 (best imaginable health state). | once before and after intake of bread for 3 weeks |
| Perceived stress measured by a Visual analog scale questionnaire | Difference in the perceived stress during a stress test between and within intervention groups after the intake of bread for 3 weeks | before the stress test, after the introduction phase, directly after the acute stress phase, 5 minutes, 10-15 minutes, 60 minutes, and 75 minutes after the stress test |
| Cognitive control using Eriksen flanker task (Flanker task) | Difference in cognitive control between and within intervention groups after the intake of bread for 3 weeks | once before and after intake of bread for 3 weeks |
| Working memory performance using a modified N-back task combined with recent-probes item-recognition task (Sternberg task) | Difference in working memory between and within intervention groups after the intake of bread for 3 weeks | once before and after intake of bread for 3 weeks |
| Electrocardiogram (ECG) using the Biopac system | Difference in heart rate variability during a stress test between and within intervention groups after the intake of bread for 3 weeks | once before and after intake of bread for 3 weeks |
| Electrodermal activity (EDA) using the Biopac system | Difference in skin conductivity during a stress test between and within intervention groups after the intake of bread for 3 weeks. Electrodes to measure EDA will be placed on the subjects' left palm. Skin conductivity measures will include skin conductivity level (SCL), the number of skin conductivity responses (SCR), and the amplitude of SCR. | once before and after intake of bread for 3 weeks |