Background: Psychological stress is well known to have consequences for human health, specifically; by increasing the risk for cardiovascular diseases, as well as contributing to decline in brain function and cerebrovascular health. Food choices during periods of stress can modify the consequences of stress for vascular health. For example, high-fat foods, which are typically preferred during stressful periods, result in worsening of vascular function both in the brain and in the peripheral vasculature. On the other hand, polyphenol interventions can prevent the harmful effects of stress on the vascular system and have been extensively shown to improve peripheral and cerebrovascular function in the absence of stress. This highlights the potential of polyphenol-rich grapes, as an alternative healthier snack, that can be protective for cardiovascular and cerebrovascular health during stressful times. Specifically, this study aims to investigate the effect of grape intake on cerebrovascular and peripheral vascular function, and cognition, in the context of an episode of psychological stress.
Methods: In a randomised, placebo-controlled, crossover, counterbalanced, double-blinded, acute study, 40 young adults (aged 18 – 40 years, gender balanced) ingested a grape drink (60 g freeze dried, equiv. to 300 g fresh containing approx. 262.2 mg of polyphenols) or a placebo (polyphenol-free, matched for all other macro and micronutrients) 1 hour before an 8-minute mental stress task (Paced-Auditory-Serial-Addition-Task, PASAT). Cognitive ability was assessed pre-and post-intervention, during which pre-frontal cortical oxygenation (measured using near-infrared spectroscopy, NIRS) was assessed. Pre-frontal cortical oxygenation was also assessed during a post-intervention baseline and during stress. Endothelial function (measured by flow-mediated dilatation, FMD) was assessed pre-intervention and 60- and 90-minutes following stress. This study is registered in clinical trials.gov (NCT number: NCT06923722, Protocol ID: ERN_17-1755H).
Results: At present, n = 36 participants (19 female, mean age: 25 ± 4 years, mean BMI: 22.7 ± 2.9 kg/m2) are enrolled in the study (n = 28 participants completed all visits). Data analysis is ongoing, but all data is planned to be analysed, and interventions unblinded, by April 2026. Data will be analysed using 2-way repeated measures ANOVAs, with time (baseline, stress, post-stress) and intervention (high or low-polyphenol grape) as main within factors.
Conclusion/significance: Stress is widespread in society and is a known risk factor for cardiovascular diseases, also affecting brain health. Outcomes from this work are expected to help inform the public about healthy food choices that are protective during periods of heightened stress.