HealthyNCT06923722
De-stressing the Brain: Can Eating Grapes During Periods of Mental Stress Protect Brain and Vascular Health in Young Adults
A study testing High-flavonoid grape intervention and Low-flavonoid grape intervention in people with Healthy, run by University of Birmingham at 1 site in United Kingdom.
Trial summary
The main aim of the current study is to investigate whether consuming grapes rich in flavonoids just before mental stress can protect cerebrovascular and peripheral vascular function, mood and cognition, from the negative effects of mental stress in young healthy adults. Read more about this study
- Who is it for?
- Ages 18 to 40 yearsHealthy volunteers can take part
- Conditions the study is for
- Healthy
- What is being tested?
- High-flavonoid grape intervention and Low-flavonoid grape intervention
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 44 participants
- Where
- 1 siteUnited Kingdom
- Study dates
- 1 Apr 2025to 31 Mar 2026
- Phase
- Interventional
- 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 40 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Males and females
- 18 - 40 years old
Who cannot join
- Smokers
- Consumes > 21 units of alcohol per week
- History of cardiovascular, respiratory, metabolic, liver or inflammatory diseases
- Suffers from blood-clotting disorders
- Allergies or intolerances to foods
- On a weight reducing dietary regiment
Show all 9Show fewer
- Currently taking dietary supplements, including fatty acids and vitamins
- On long-term medication or have been on antibiotics in the last 3 months
- Has an infection at present (e.g. cold) or viral infection
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
United Kingdom1 site, 1 recruiting
- Recruiting
School of Sport, Exercise & Rehabilitation Sciences
Birmingham, West Midlands, B15 2TT
Catarina Rendeiro, +44 7389190669, c.rendeiro@bham.ac.uk
About this study
Official title: A Placebo-controlled, Randomized, Double-masked, Cross-over Acute Intervention Study Investigating the Effects of Grape Polyphenols on Cerebral Oxygenation, Cognitive and Vascular Function in the Context of Mental Stress in Young Adults
The main aim of the current study is to investigate whether consuming grapes rich in flavonoids just before mental stress can protect cerebrovascular and peripheral vascular function, mood and cognition, from the negative effects of mental stress in young healthy adults. A second, exploratory aim, will further address whether quality of habitual diet, microbiome health (composition; metabolites production e.g. Short-chain fatty acids) and levels of cardiorespiratory fitness play a role on the beneficial effects of grapes during mental stress. All participants will receive a high-flavonoid grape intervention (60 g freeze-dried grape powder, equivalent to 300 g fresh grapes) and a low-flavonoid grape intervention (60 g powdere isocaloric-matched control). It is hypothesized that the high-flavonoid grape intervention will improve cortical oxygenation and cognitive function in the context of mental stress, and prevent the stress-induced decline in peripheral endothelial function following stress. Furthermore, it is hypothesized that individuals with poorer diets, cardiorespiratory fitness and a poorer gut microbiome will benefit more from the grape intervention in the context of mental stress.
Read the detailed description
Psychological stress is widespread in our societies, and has been extensively shown to have negative consequences for human health. Specifically, psychological stress induces significant declines in human vascular function, as measured by brachial Flow-mediated Dilatation (FMD). We have demonstrated that flavonoid interventions can prevent the harmful effects of stress on the vascular system. Indeed, flavonoid-rich interventions have also been extensively shown to improve peripheral and cerebrovascular function in the absence of stress. However, the effect of flavonoids on cerebrovascular function and cognition in the context of mental stress is unknown. In the proposed project, our key objectives are to investigate whether grape intake prior to a mental stress task results in better brain oxygenation and vascular function, which leads to improved cognitive performance and mood in young healthy adults. These data will establish whether grapes can be effective as a 'stress snack' to optimize cognitive and brain function in the context of psychological stress. Furthermore, we will explore whether there are certain participant characteristics that mediate the impact of grape flavonoids on cerebrovascular function and cognition in the context of mental stress. Such as, physical fitness (assessed by a VO2 max test), composition of gut microbiome (assessed by faecal sample), habitual diet (assessed by 3-day food diary and the food frequency questionnaire), and eating behaviour and chronic stress (assessed by the eating behaviour questionnaire and perceived stress scale). This work will be important to guide future dietary recommendations around stress and might ultimately result in increased intake of flavonoid-rich grapes and other flavonoid-rich fruits/vegetables overall.
- Conditions
- Healthy
- Being tested
- High-flavonoid grape intervention, Low-flavonoid grape intervention
- Keywords
- vascular function, flavonoids, cerebral oxygenation, mental stress, cognition, executive function, grape, Flow-mediated dilatation, Functional Near-Infrared Spectroscopy
- Medical subject headings
- Stress, Psychological
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
High-flavonoid grape interventionDietary supplement
High-flavonoid grape powder: 60 g, equivalent to 300 g fresh grapes. Total polyphenols: 437 mg/100g).
Low-flavonoid grape interventionDietary supplement
60 g powder isocaloric-matched control (Total polyphenols: < 60 mg)
| Study group | Role | What they receive |
|---|---|---|
| High-flavonoid grape intervention | Experimental | 60 g freeze-dried grape powder, equivalent to 300 g fresh grapes (Total polyphenols: 437 mg/100g) Receives: Dietary Supplement: High-flavonoid grape intervention |
| Low-flavonoid grape intervention | Placebo comparator | 60 g powder isocaloric-matched control (Total polyphenols: < 60 mg) Receives: Dietary Supplement: Low-flavonoid grape intervention |
What is being measured
The primary outcome is the main question the study is designed to answer.
Pre-frontal cortical Tissue Oxygenation Index (NIRS) - TOI
Pre-frontal levels of Tissue Oxygenation Index (% TOI) will be assessed by functional Near-Infrared Spectroscopy (fNIRS). The NIRS device measures changes in chromophore concentrations of oxyhaemoglobin (O2Hb) and deoxyhaemoglobin (HHb), providing depth-resolved measures of total tissue oxygen saturation.
Measured: Change from pre-intervention baseline to 1 hour post-intervention (during mental stress) and 1 hour 15 minutes post-intervention (during cognitive tasks, 10 minutes post-stress)
Pre-frontal cortical Tissue Oxygenation Index (NIRS) - O2Hb
Pre-frontal levels of oxygenated (O2Hb) haemoglobin concentration (μmol) will be assessed by functional Near-Infrared Spectroscopy (fNIRS).
Measured: Change from pre-intervention baseline to 1 hour post-intervention (during mental stress) and 1 hour 15 minutes post-intervention (during cognitive tasks, 10 minutes post-stress).
Pre-frontal cortical Tissue Oxygenation Index (NIRS) - HHb
Pre-frontal levels of deoxygenated (HHb) haemoglobin concentration (μmol) will be assessed by functional Near-Infrared Spectroscopy (fNIRS).
Measured: Change from pre-intervention baseline to 1 hour post-intervention (during mental stress) and 1 hour 15 minutes post-intervention (during cognitive tasks, 10 minutes post-stress).
Pre-frontal cortical Tissue Oxygenation Index (NIRS) - nTHI
Pre-frontal levels of normalised haemoglobin index (relative value of total haemoglobin normalised to the initial value, nTHI) content (a.u.) will be assessed by functional Near-Infrared Spectroscopy (fNIRS).
Measured: Change from pre-intervention baseline to 1 hour post-intervention (during mental stress) and 1 hour 15 minutes post-intervention (during cognitive tasks, 10 minutes post-stress).
Secondary outcomes (10)
Flow-mediated dilatation (FMD) of the brachial artery
FMD of the brachial artery. Expressed as % FMD: change in brachial diameter from baseline to peak dilation following 5 minutes of arterial occlusion. Brachial artery diameter and blood flow will be measured using Doppler ultrasonography (uSmart 3300, Terason).
Measured: Change from pre-intervention baseline to 2 hours and 2 hours 45 minutes post-intervention (45-90 minutes post-stress).
Common Carotid Artery (CCA) - Blood flow
Common Carotid Artery (CCA) blood flow velocity (ml min-1) will be measured using Doppler ultrasonography (uSmart 3300, Terason) interfaced with the Quipu analysis software. CCA blood flow is calculated using CCA blood velocity and diameter across 2 minutes of recording.
Measured: Change from pre-intervention baseline to 2 hours and 2 hours 45 minutes post-intervention (45-90 minutes post-stress).
Common Carotid Artery (CCA) - Shear rate
Common Carotid Artery (CCA) shear rate (s-1) will be measured using Doppler ultrasonography (uSmart 3300, Terason) interfaced with the Quipu analysis software.
Measured: Change from pre-intervention baseline to 2 hours and 2 hours 45 minutes post-intervention (45-90 minutes post-stress).
Executive Function (MANT) - Accuracy
Executive function accuracy will be measured using the Modified Attention Network Task (MANT) which measures response to cognitive load
Measured: Change from pre-intervention baseline to 1 hour 15 minutes post-intervention (10 minutes post-stress).
Executive Function (Switch) - Accuracy
Executive function accuracy will be measured using the Switch Task which considers cognitive flexibility.
Measured: Change from pre-intervention baseline to 1 hour 15 minutes post-intervention (10 minutes post-stress).
Executive Function (MANT) - Reaction time
Executive function reaction time will be measured using Modified Attention Network Task (MANT) which measures response to cognitive load.
Measured: Change from pre-intervention baseline to 1 hour 15 minutes post-intervention (10 minutes post-stress).
Executive Function (Switch) - Reaction time
Executive function reaction time will be measured using the Switch Task which considers cognitive flexibility.
Measured: Change from pre-intervention baseline to 1 hour 15 minutes post-intervention (10 minutes post-stress).
Executive Function (MANT) - Inverse Efficiency Score
Executive function inverse efficiency will be measured using the Modified Attention Network Task (MANT), calculated by dividing task reaction time by task accuracy.
Measured: Change from pre-intervention baseline to 1 hour 15 minutes post-intervention (10 minutes post-stress).
Executive Function (Switch) - Inverse Efficiency Score
Executive function inverse efficiency will be measured using the Switch Task, calculated by dividing task reaction time by task accuracy.
Measured: Change from pre-intervention baseline to 1 hour 15 minutes post-intervention (10 minutes post-stress).
Mood (POMS)
Mood (total mood disturbance, TMD) will be assessed by the questionnaire Profile-of-Mood-States (POMS).
Measured: Change from pre-intervention baseline to 1 hour post-intervention (immediately following stress), 2 hours and 2 hours 45 minutes post-intervention (45-90 minutes post-stress).
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted11 Apr 2025
- Study start1 Apr 2025
- Primary completion31 Mar 2026 (estimated)
- Study completion31 Mar 2026 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for HealthyStudies 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
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Triple blind
- Who is masked
- Participant, Investigator, Outcomes assessor
- Enrolment
- 44 participants (estimated)
Sponsor and investigators
- Lead sponsor
- University of Birmingham
- Sponsor type
- University, hospital or other
- Collaborators
- California Table Grape Commission
- Responsible party
- Principal investigator, Catarina Rendeiro, University of Birmingham
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06923722
- Sponsor's protocol ID
- ERN_17-1755H
- Other IDs
- 3155902
- Status last verified
- Dec 2025
- First submitted
- 27 Mar 2025
- Last updated
- 4 Dec 2025
- 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 4 Dec 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- A Placebo-controlled, Randomized, Double-masked, Cross-over Acute Intervention Study Investigating the Effects of Grape Polyphenols on Cerebral Oxygenation, Cognitive and Vascular Function in the Context of Mental Stress in Young Adults
- ClinicalTrials.gov ID
- NCT06923722
- Acronym / sponsor ID
- ERN_17-1755H
- Conditions
- Healthy
- Keywords
- vascular function, flavonoids, cerebral oxygenation, mental stress, cognition, executive function, grape, Flow-mediated dilatation
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 44 participants (estimated)
- Lead sponsor
- University of BirminghamUniversity, hospital or other
- Collaborators
- California Table Grape Commission
- Study start
- 1 Apr 2025 (actual)
- Primary completion
- 31 Mar 2026 (estimated)
- Study completion
- 31 Mar 2026 (estimated)
- First posted
- 11 Apr 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 main aim of the current study is to investigate whether consuming grapes rich in flavonoids just before mental stress can protect cerebrovascular and peripheral vascular function, mood and cognition, from the negative effects of mental stress in young healthy adults. A second, exploratory aim, will further address whether quality of habitual diet, microbiome health (composition; metabolites production e.g. Short-chain fatty acids) and levels of cardiorespiratory fitness play a role on the beneficial effects of grapes during mental stress. All participants will receive a high-flavonoid grape intervention (60 g freeze-dried grape powder, equivalent to 300 g fresh grapes) and a low-flavonoid grape intervention (60 g powdere isocaloric-matched control). It is hypothesized that the high-flavonoid grape intervention will improve cortical oxygenation and cognitive function in the context of mental stress, and prevent the stress-induced decline in peripheral endothelial function following stress. Furthermore, it is hypothesized that individuals with poorer diets, cardiorespiratory fitness and a poorer gut microbiome will benefit more from the grape intervention in the context of mental stress.
Detailed description
Psychological stress is widespread in our societies, and has been extensively shown to have negative consequences for human health. Specifically, psychological stress induces significant declines in human vascular function, as measured by brachial Flow-mediated Dilatation (FMD). We have demonstrated that flavonoid interventions can prevent the harmful effects of stress on the vascular system. Indeed, flavonoid-rich interventions have also been extensively shown to improve peripheral and cerebrovascular function in the absence of stress. However, the effect of flavonoids on cerebrovascular function and cognition in the context of mental stress is unknown. In the proposed project, our key objectives are to investigate whether grape intake prior to a mental stress task results in better brain oxygenation and vascular function, which leads to improved cognitive performance and mood in young healthy adults. These data will establish whether grapes can be effective as a 'stress snack' to optimize cognitive and brain function in the context of psychological stress. Furthermore, we will explore whether there are certain participant characteristics that mediate the impact of grape flavonoids on cerebrovascular function and cognition in the context of mental stress. Such as, physical fitness (assessed by a VO2 max test), composition of gut microbiome (assessed by faecal sample), habitual diet (assessed by 3-day food diary and the food frequency questionnaire), and eating behaviour and chronic stress (assessed by the eating behaviour questionnaire and perceived stress scale). This work will be important to guide future dietary recommendations around stress and might ultimately result in increased intake of flavonoid-rich grapes and other flavonoid-rich fruits/vegetables overall.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Triple blind (participant, investigator, outcomes assessor)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| High-flavonoid grape intervention | Experimental | Dietary Supplement: High-flavonoid grape intervention60 g freeze-dried grape powder, equivalent to 300 g fresh grapes (Total polyphenols: 437 mg/100g) |
| Low-flavonoid grape intervention | Placebo comparator | Dietary Supplement: Low-flavonoid grape intervention60 g powder isocaloric-matched control (Total polyphenols: < 60 mg) |
Who may qualify
- Ages
- 18 to 40 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (2 listed)
- Males and females
- 18 - 40 years old
Key exclusion criteria (9 listed)
- Smokers
- Consumes > 21 units of alcohol per week
- History of cardiovascular, respiratory, metabolic, liver or inflammatory diseases
- Suffers from blood-clotting disorders
- Allergies or intolerances to foods
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 |
|---|---|---|
| High-flavonoid grape interventionHigh-flavonoid grape powder: 60 g, equivalent to 300 g fresh grapes. Total polyphenols: 437 mg/100g). | Dietary supplement | High-flavonoid grape intervention |
| Low-flavonoid grape intervention60 g powder isocaloric-matched control (Total polyphenols: < 60 mg) | Dietary supplement | Low-flavonoid grape intervention |
Primary outcome
Pre-frontal cortical Tissue Oxygenation Index (NIRS) - TOI
Time frame: Change from pre-intervention baseline to 1 hour post-intervention (during mental stress) and 1 hour 15 minutes post-intervention (during cognitive tasks, 10 minutes post-stress)
Pre-frontal levels of Tissue Oxygenation Index (% TOI) will be assessed by functional Near-Infrared Spectroscopy (fNIRS). The NIRS device measures changes in chromophore concentrations of oxyhaemoglobin (O2Hb) and deoxyhaemoglobin (HHb), providing depth-resolved measures of total tissue oxygen saturation.
Pre-frontal cortical Tissue Oxygenation Index (NIRS) - O2Hb
Time frame: Change from pre-intervention baseline to 1 hour post-intervention (during mental stress) and 1 hour 15 minutes post-intervention (during cognitive tasks, 10 minutes post-stress).
Pre-frontal levels of oxygenated (O2Hb) haemoglobin concentration (μmol) will be assessed by functional Near-Infrared Spectroscopy (fNIRS).
Pre-frontal cortical Tissue Oxygenation Index (NIRS) - HHb
Time frame: Change from pre-intervention baseline to 1 hour post-intervention (during mental stress) and 1 hour 15 minutes post-intervention (during cognitive tasks, 10 minutes post-stress).
Pre-frontal levels of deoxygenated (HHb) haemoglobin concentration (μmol) will be assessed by functional Near-Infrared Spectroscopy (fNIRS).
Pre-frontal cortical Tissue Oxygenation Index (NIRS) - nTHI
Time frame: Change from pre-intervention baseline to 1 hour post-intervention (during mental stress) and 1 hour 15 minutes post-intervention (during cognitive tasks, 10 minutes post-stress).
Pre-frontal levels of normalised haemoglobin index (relative value of total haemoglobin normalised to the initial value, nTHI) content (a.u.) will be assessed by functional Near-Infrared Spectroscopy (fNIRS).
10 secondary outcomes
Flow-mediated dilatation (FMD) of the brachial artery
Time frame: Change from pre-intervention baseline to 2 hours and 2 hours 45 minutes post-intervention (45-90 minutes post-stress).
Common Carotid Artery (CCA) - Blood flow
Time frame: Change from pre-intervention baseline to 2 hours and 2 hours 45 minutes post-intervention (45-90 minutes post-stress).
Common Carotid Artery (CCA) - Shear rate
Time frame: Change from pre-intervention baseline to 2 hours and 2 hours 45 minutes post-intervention (45-90 minutes post-stress).
Executive Function (MANT) - Accuracy
Time frame: Change from pre-intervention baseline to 1 hour 15 minutes post-intervention (10 minutes post-stress).
Executive Function (Switch) - Accuracy
Time frame: Change from pre-intervention baseline to 1 hour 15 minutes post-intervention (10 minutes post-stress).
Executive Function (MANT) - Reaction time
Time frame: Change from pre-intervention baseline to 1 hour 15 minutes post-intervention (10 minutes post-stress).
Executive Function (Switch) - Reaction time
Time frame: Change from pre-intervention baseline to 1 hour 15 minutes post-intervention (10 minutes post-stress).
Executive Function (MANT) - Inverse Efficiency Score
Time frame: Change from pre-intervention baseline to 1 hour 15 minutes post-intervention (10 minutes post-stress).
Executive Function (Switch) - Inverse Efficiency Score
Time frame: Change from pre-intervention baseline to 1 hour 15 minutes post-intervention (10 minutes post-stress).
Mood (POMS)
Time frame: Change from pre-intervention baseline to 1 hour post-intervention (immediately following stress), 2 hours and 2 hours 45 minutes post-intervention (45-90 minutes post-stress).
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 4 Dec 2025.
- 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.
School of Sport, Exercise & Rehabilitation Sciences
Birmingham, United Kingdom
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing High-flavonoid grape intervention and Low-flavonoid grape intervention in people with Healthy, run by University of Birmingham at 1 site in United Kingdom.
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 2 inclusion and 9 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 4 Dec 2025. 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 United Kingdom. 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. Some participants in this study may receive a placebo. 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?
Each site lists its own contact: choose the nearest one under Trial locations. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Pre-frontal cortical Tissue Oxygenation Index (NIRS) - TOI (time frame: Change from pre-intervention baseline to 1 hour post-intervention (during mental stress) and 1 hour 15 minutes post-intervention (during cognitive tasks, 10 minutes post-stress)). The study lists 4 primary outcomes in all. 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 4 Dec 2025.