The Effects of a Single Dose of Wild Blueberries on Mood and Cognition in Healthy Young Adults

The Effects of a Single Dose of Wild Blueberries on Mood and Cognition in Healthy Young Adults: a Randomized, Double-blind, Placebo-controlled, Crossover Study

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.

Study Overview

• Status: Completed
• Conditions: Mood; Cognition; Affect
• Intervention / Treatment: Dietary supplement: Wild blueberry powder; Dietary supplement: Placebo powder

Detailed Description

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
• Enrollment (Actual): 33
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United Kingdom
  • Berkshire
    • Reading, Berkshire, United Kingdom, RG6 6AL
      • School of Psychology and Clinical Languages, University of Reading

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 25 years (Adult)
• Accepts Healthy Volunteers: Yes
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• 18 to 25 years of age
• Willingness to provide blood samples

Exclusion Criteria:

• Allergy to blueberries or any other Vaccinium species
• Diagnosis or symptoms of anxiety, depression, or other mental health conditions
• Any medically significant condition (e.g. anemia, gastrointestinal disorders, diabetes)
• Use of psychoactive medication or recreational drugs in the last two weeks
• Current use of medication that could interact with the intervention (e.g. antibiotics)
• Obesity or underweight
• Participation in other interventional studies in the last month
• Pregnancy or lactation

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Triple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Blueberry/Placebo; In this arm, participants will receive the blueberry intervention first, followed by the placebo one week later.	Dietary supplement: Wild blueberry powder; 22 g freeze-dried wild blueberry (Vaccinium angustifolium) powder, mixed with 250 ml water, and served in an opaque container.; Dietary supplement: Placebo powder; 22 g placebo powder matched for macronutrients and flavor, mixed with 250 ml water, and served in an opaque container.
Experimental: Placebo/Blueberry; In this arm, participants will receive the placebo first, followed by the blueberry intervention one week later.	Dietary supplement: Wild blueberry powder; 22 g freeze-dried wild blueberry (Vaccinium angustifolium) powder, mixed with 250 ml water, and served in an opaque container.; Dietary supplement: Placebo powder; 22 g placebo powder matched for macronutrients and flavor, mixed with 250 ml water, and served in an opaque container.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
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.	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	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).	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).	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).	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).	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).	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).	2 hours post-ingestion
Serum brain-derived neurotrophic factor (BDNF)	Serum levels of BDNF will be analyzed using enzyme-linked immunosorbent assay (ELISA).	baseline
Serum brain-derived neurotrophic factor (BDNF)	Serum levels of BDNF will be analyzed using enzyme-linked immunosorbent assay (ELISA).	2 hours post-ingestion

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
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.	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.	2 hours post-ingestion
Reaction time to positive stimuli	The average reaction time to correctly categorized happy faces in the facial expression task.	baseline
Reaction time to positive stimuli	The average reaction time to correctly categorized happy faces in the facial expression task.	2 hours post-ingestion
Reaction time to negative stimuli	The average reaction time to correctly categorized angry faces in the facial expression task.	baseline
Reaction time to negative stimuli	The average reaction time to correctly categorized angry faces in the facial expression task.	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.	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.	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.	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.	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.	baseline
Choice reaction time (post-switch trials)	The average reaction time of correct responses to post-switch trials of the task-switching test.	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.	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.	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.	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.	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.	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.	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).	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).	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.	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.	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.	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.	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.	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.	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.	baseline
Serum monoamine oxidase B (MAO-B) inhibition	The activity of the enzyme MAO-B in serum will be analyzed using a fluorometric assay.	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.	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.	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.	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.	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.	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.	2 hours post-ingestion

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Recognition memory on RAVLT	In the final task of the Rey Auditory Verbal Learning Test, participants need to recognize the 15 words from List A from a list of 50 words. Recognition memory is defined as the number of correctly recognized words out of the total number of words.	baseline
Recognition memory on RAVLT	In the final task of the Rey Auditory Verbal Learning Test, participants need to recognize the 15 words from List A from a list of 50 words. Recognition memory is defined as the number of correctly recognized words out of the total number of words.	2 hours post-ingestion

Collaborators and Investigators

• Sponsor: University of Reading
• Collaborators: Wild Blueberry Association of North America (WBANA)

Study record dates

Study Major Dates

• Study Start (Actual): May 26, 2021
• Primary Completion (Actual): August 27, 2021
• Study Completion (Actual): August 27, 2021

Study Registration Dates

• First Submitted: May 27, 2021
• First Submitted That Met QC Criteria: June 9, 2021
• First Posted (Actual): June 22, 2021

Study Record Updates

• Last Update Posted (Actual): September 21, 2021
• Last Update Submitted That Met QC Criteria: September 20, 2021
• Last Verified: September 1, 2021

More Information

Terms related to this study

• Keywords: flavonoids; anthocyanins; blueberry
• Other Study ID Numbers: 21/09

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Sharing Supporting Information Type: SAP

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No