This study aims to investigate whether consuming a drink containing powdered blueberries (equivalent to 150 g fresh fruit) can improve mood and cognition in healthy young adults. Blood biomarkers of inflammation and neurotransmitter turnover will be analyzed as well as responses to computer-based cognitive tasks designed to measure verbal memory, executive function, and emotional processing.
The present study will examine the psychological effects of a single dose of freeze-dried wild blueberries using a randomized, double-blind, placebo-controlled, counterbalanced, crossover design. A total of 30 healthy young adults will consume two drinks: one containing 22 g blueberry powder and the other containing 22 g matched placebo powder in counterbalanced order one week apart. The investigators will assess changes in transient mood, cognitive-emotional function, and serum biomarkers of inflammation, neuroplasticity, and monoamine metabolism from baseline to 2 hours post-ingestion.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
TRIPLE
Enrollment
33
22 g freeze-dried wild blueberry (Vaccinium angustifolium) powder, mixed with 250 ml water, and served in an opaque container.
22 g placebo powder matched for macronutrients and flavor, mixed with 250 ml water, and served in an opaque container.
School of Psychology and Clinical Languages, University of Reading
Reading, Berkshire, United Kingdom
Global transient mood as measured by PANAS-X
The Positive and Negative Affect Schedule - Expanded Form (PANAS-X) is a validated, self-rated measure of affective state, encompassing two general dimensions (positive and negative affect). These will be calculated separately by adding the values of the individual items (21 positive and 25 negative items). Thus, the scales will range from 0 to 84 points for positive affect and from 0 to 100 for negative affect, with a higher score indicating greater positive or negative affect. Positive affect will be considered the primary measure.
Time frame: baseline
Global transient mood as measured by PANAS-X
The Positive and Negative Affect Schedule - Expanded Form (PANAS-X) is a validated, self-rated measure of affective state, encompassing two general dimensions (positive and negative affect). These will be calculated separately by adding the values of the individual items (21 positive and 25 negative items). Thus, the scales will range from 0 to 84 points for positive affect and from 0 to 100 for negative affect, with a higher score indicating greater positive or negative affect. Positive affect will be considered the primary measure
Time frame: 2 hours post-ingestion
Negative interpretation bias
A negative interpretation bias is defined as a tendency to interpret ambiguous information in a consistently threatening or negative manner, thus serving as an objective indicator of affective state. In this task, participants will be asked to categorize facial expressions of anger, happiness, and surprise as either positive or negative. Interpretation bias will be operationalized as the percent of trials in which surprised faces were rated as negative, out of the total number of surprise trials (48 trials).
Time frame: baseline
Negative interpretation bias
A negative interpretation bias is defined as a tendency to interpret ambiguous information in a consistently threatening or negative manner, thus serving as an objective indicator of affective state. In this task, participants will be asked to categorize facial expressions of anger, happiness, and surprise as either positive or negative. Interpretation bias will be operationalized as the percent of trials in which surprised faces were rated as negative, out of the total number of surprise trials (48 trials).
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Time frame: 2 hours post-ingestion
Cognitive flexibility (accuracy on post-switch trials)
A task-switching test will be used to assess cognitive performance when switching between two predictable tasks requiring simple numerical decisions. The main outcome of interest is the average accuracy of responses to post-switch trials (those immediately following a switch to a new task).
Time frame: baseline
Cognitive flexibility (accuracy on post-switch trials)
A task-switching test will be used to assess cognitive performance when switching between two predictable tasks requiring simple numerical decisions. The main outcome of interest is the average accuracy of responses to post-switch trials (those immediately following a switch to a new task).
Time frame: 2 hours post-ingestion
Delayed verbal memory on RAVLT
The Rey Auditory Verbal Learning Test (RAVLT) is a standard neuropsychological assessment designed to evaluate verbal memory. The participant hears a list of 15 words and is asked to recall as many words as possible. This procedure is repeated five times. The main outcome of interest is the number of correctly recalled words 20 minutes after the last presentation of the list of words (Trial A7).
Time frame: baseline
Delayed verbal memory on RAVLT
The Rey Auditory Verbal Learning Test (RAVLT) is a standard neuropsychological assessment designed to evaluate verbal memory. The participant hears a list of 15 words and is asked to recall as many words as possible. This procedure is repeated five times. The main outcome of interest is the number of correctly recalled words 20 minutes after the last presentation of the list of words (Trial A7).
Time frame: 2 hours post-ingestion
Serum brain-derived neurotrophic factor (BDNF)
Serum levels of BDNF will be analyzed using enzyme-linked immunosorbent assay (ELISA).
Time frame: baseline
Serum brain-derived neurotrophic factor (BDNF)
Serum levels of BDNF will be analyzed using enzyme-linked immunosorbent assay (ELISA).
Time frame: 2 hours post-ingestion
Distinct affective states as measured by PANAS-X subscales
The following affective states will be examined separately as defined by the PANAS-X subscales: Joviality (Happiness), Self-Assurance, Attentiveness, Fatigue, Serenity. Higher scores will indicate greater intensity of the respective affective state.
Time frame: baseline
Distinct affective states as measured by PANAS-X subscales
The following affective states will be examined separately as defined by the PANAS-X subscales: Joviality (Happiness), Self-Assurance, Attentiveness, Fatigue, Serenity. Higher scores will indicate greater intensity of the respective affective state.
Time frame: 2 hours post-ingestion
Reaction time to positive stimuli
The average reaction time to correctly categorized happy faces in the facial expression task.
Time frame: baseline
Reaction time to positive stimuli
The average reaction time to correctly categorized happy faces in the facial expression task.
Time frame: 2 hours post-ingestion
Reaction time to negative stimuli
The average reaction time to correctly categorized angry faces in the facial expression task.
Time frame: baseline
Reaction time to negative stimuli
The average reaction time to correctly categorized angry faces in the facial expression task.
Time frame: 2 hours post-ingestion
Attentional bias to emotional information
Attentional bias to emotional information will be operationalized as the average reaction time to correctly categorized angry faces divided by the average reaction time to correctly categorized happy faces. Thus, a higher value indicates a tendency to attend to and process positive information over negative information.
Time frame: baseline
Attentional bias to emotional information
Attentional bias to emotional information will be operationalized as the average reaction time to correctly categorized angry faces divided by the average reaction time to correctly categorized happy faces. Thus, a higher value indicates a tendency to attend to and process positive information over negative information.
Time frame: 2 hours post-ingestion
Cognitive flexibility (accuracy on remaining trials of task-switching test)
The average accuracy (in %) of responses to the remaining trials of the task-switching test will be measured as a secondary outcome. In this task, participants have to switch between two predictable tasks requiring simple numerical decisions.
Time frame: baseline
Cognitive flexibility (accuracy on remaining trials of task-switching test)
The average accuracy (in %) of responses to the remaining trials of the task-switching test will be measured as a secondary outcome. In this task, participants have to switch between two predictable tasks requiring simple numerical decisions.
Time frame: 2 hours post-ingestion
Choice reaction time (post-switch trials)
The average reaction time of correct responses to post-switch trials of the task-switching test.
Time frame: baseline
Choice reaction time (post-switch trials)
The average reaction time of correct responses to post-switch trials of the task-switching test.
Time frame: 2 hours post-ingestion
Choice reaction time (remaining trials of task-switching test)
The average reaction time of correct responses to remaining trials of the task-switching test.
Time frame: baseline
Choice reaction time (remaining trials of task-switching test)
The average reaction time of correct responses to remaining trials of the task-switching test.
Time frame: 2 hours post-ingestion
Final acquisition on RAVLT (Trial 5)
The number of correctly retrieved words on Trial 5 (List A) of the Rey Auditory Verbal Learning Test.
Time frame: baseline
Final acquisition on RAVLT (Trial 5)
The number of correctly retrieved words on Trial 5 (List A) of the Rey Auditory Verbal Learning Test.
Time frame: 2 hours post-ingestion
Recall of interference list on RAVLT
The number of correctly retrieved words from the interference list (List B) of the Rey Auditory Verbal Learning Test.
Time frame: baseline
Recall of interference list on RAVLT
The number of correctly retrieved words from the interference list (List B) of the Rey Auditory Verbal Learning Test.
Time frame: 2 hours post-ingestion
Immediate recall on RAVLT
The number of correctly recalled words on the Rey Auditory Verbal Learning Test 2 minutes after the final presentation of List A (and following the presentation and recall of List B).
Time frame: baseline
Immediate recall on RAVLT
The number of correctly recalled words on the Rey Auditory Verbal Learning Test 2 minutes after the final presentation of List A (and following the presentation and recall of List B).
Time frame: 2 hours post-ingestion
Proactive interference on RAVLT
Proactive interference on the Rey Auditory Verbal Learning Test is defined as the number of correctly recalled words from the interference List B divided by the number of correctly recalled words on Trial 1 of List A (B1/A1). A higher score indicates less proactive interference.
Time frame: baseline
Proactive interference on RAVLT
Proactive interference on the Rey Auditory Verbal Learning Test is defined as the number of correctly recalled words from the interference List B divided by the number of correctly recalled words on Trial 1 of List A (B1/A1). A higher score indicates less proactive interference.
Time frame: 2 hours post-ingestion
Retroactive interference on RAVLT
Retroactive interference on the Rey Auditory Verbal Learning Test is defined as the number of correctly recalled words on Trial 6 of List A (the free recall trial after the interference List B) divided by the number of correctly recalled words on Trial 5 of List A (A6/A5). A higher score indicates less retroactive interference.
Time frame: baseline
Retroactive interference on RAVLT
Retroactive interference on the Rey Auditory Verbal Learning Test is defined as the number of correctly recalled words on Trial 6 of List A (the free recall trial after the interference List B) divided by the number of correctly recalled words on Trial 5 of List A (A6/A5). A higher score indicates less retroactive interference.
Time frame: 2 hours post-ingestion
Retention on RAVLT
Retention on the Rey Auditory Verbal Learning Test is defined as the number of correctly recalled words on Trial 7 of List A (the delayed recall trial at 20 minutes) divided by the number of correctly retrieved words on Trial 6 of List A (A7/A6). Thus, a higher score indicates a higher retention rate.
Time frame: baseline
Retention on RAVLT
Retention on the Rey Auditory Verbal Learning Test is defined as the number of correctly recalled words on Trial 7 of List A (the delayed recall trial at 20 minutes) divided by the number of correctly retrieved words on Trial 6 of List A (A7/A6). Thus, a higher score indicates a higher retention rate.
Time frame: 2 hours post-ingestion
Serum monoamine oxidase B (MAO-B) inhibition
The activity of the enzyme MAO-B in serum will be analyzed using a fluorometric assay.
Time frame: baseline
Serum monoamine oxidase B (MAO-B) inhibition
The activity of the enzyme MAO-B in serum will be analyzed using a fluorometric assay.
Time frame: 2 hours post-ingestion
Serum 3,4-dihydroxyphenylglycol (DHPG)
Serum levels of DHPG will be analyzed using liquid chromatography-mass spectrometry (LS-MS) to indirectly determine monoamine oxidase A (MAO-A) activity.
Time frame: baseline
Serum 3,4-dihydroxyphenylglycol (DHPG)
Serum levels of DHPG will be analyzed using liquid chromatography-mass spectrometry (LS-MS) to indirectly determine monoamine oxidase A (MAO-A) activity.
Time frame: 2 hours post-ingestion
Serum interleukin-6 (IL-6)
Serum levels of IL-6 will be analyzed using enzyme-linked immunosorbent assay (ELISA) as an indication of systemic inflammation.
Time frame: baseline
Serum interleukin-6 (IL-6)
Serum levels of IL-6 will be analyzed using enzyme-linked immunosorbent assay (ELISA) as an indication of systemic inflammation.
Time frame: 2 hours post-ingestion
Serum C-reactive protein (CRP)
Serum levels of CRP will be analyzed using enzyme-linked immunosorbent assay (ELISA) as an indication of systemic inflammation.
Time frame: baseline
Serum C-reactive protein (CRP)
Serum levels of CRP will be analyzed using enzyme-linked immunosorbent assay (ELISA) as an indication of systemic inflammation.
Time frame: 2 hours post-ingestion