De-stressing the Brain: Can Eating Grapes During Periods of Mental Stress Protect Brain and Vascular Health in Young Adults

NCT06923722 | Recruiting

• 2 other identifiers: ERN_17-1755H3155902
• Study Type: interventional
• Target: 44
• Locations: 1 country
• Sites: 1

Brief 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. 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.

Conditions

Healthy

Keywords

vascular function; flavonoids; cerebral oxygenation; mental stress; cognition; executive function; grape; Flow-mediated dilatation; Functional Near-Infrared Spectroscopy

Outcome Measures

Primary Outcomes (4)

• 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.

  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).

  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).

  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).

  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

  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

  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

  Change from pre-intervention baseline to 2 hours and 2 hours 45 minutes post-intervention (45-90 minutes post-stress).

• Executive Function (MANT) - Accuracy

  Change from pre-intervention baseline to 1 hour 15 minutes post-intervention (10 minutes post-stress).

• Executive Function (Switch) - Accuracy

  Change from pre-intervention baseline to 1 hour 15 minutes post-intervention (10 minutes post-stress).

Other Outcomes (10)

• Forearm blood flow (FBF)

  Change from pre-intervention baseline to 1 hour post-intervention (during 8 minutes rest and 8 minutes of mental stress).

• Forearm vascular conductance (FVC)

  Change from pre-intervention baseline to 1 hour post-intervention (during 8 minutes rest and 8 minutes of mental stress).

• Cardiovascular activity - Heart rate (HR)

  Change from pre-intervention baseline to 1 hour post-intervention (during 8 minutes rest and 8 minutes of mental stress).

Study Arms (2)

High-flavonoid grape intervention

EXPERIMENTAL

60 g freeze-dried grape powder, equivalent to 300 g fresh grapes (Total polyphenols: 437 mg/100g)

Dietary Supplement: High-flavonoid grape intervention

Low-flavonoid grape intervention

PLACEBO COMPARATOR

60 g powder isocaloric-matched control (Total polyphenols: \< 60 mg)

Dietary Supplement: Low-flavonoid grape intervention

Interventions

High-flavonoid grape intervention DIETARY_SUPPLEMENT

High-flavonoid grape powder: 60 g, equivalent to 300 g fresh grapes. Total polyphenols: 437 mg/100g).

High-flavonoid grape intervention

Low-flavonoid grape intervention DIETARY_SUPPLEMENT

60 g powder isocaloric-matched control (Total polyphenols: \< 60 mg)

Low-flavonoid grape intervention

Eligibility Criteria

• Age: 18 Years - 40 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• Males and females
• years old

You may not qualify if:

• 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
• 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

Sponsors & Collaborators

• University of Birmingham: lead
• California Table Grape Commission: collaborator

Study Sites (1)

School of Sport, Exercise & Rehabilitation Sciences

Birmingham, West Midlands, B15 2TT, United Kingdom

RECRUITING

MeSH Terms

Conditions

Stress, Psychological

Condition Hierarchy (Ancestors)

Behavioral Symptoms; Behavior

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: TRIPLE
• Who Masked: PARTICIPANT, INVESTIGATOR, OUTCOMES ASSESSOR
• Masking Details: The interventions have been masked by the intervention supplier (California Table Grape Commission). Therefore, all researchers are blinded to the conditions.
• Purpose: TREATMENT
• Intervention Model: CROSSOVER
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Principal Investigator, Assistant Professor in Nutritional Sciences

Study Record Dates

• First Submitted: March 27, 2025
• First Posted: April 11, 2025
• Study Start: April 1, 2025
• Primary Completion: March 31, 2026
• Study Completion: March 31, 2026
• Last Updated: December 4, 2025

Record last verified: 2025-12

Data Sharing

• IPD Sharing: Will not share

Locations

GB (1)