Neural Effects of Green Tea Extract on Dorsolateral Prefrontal Cortex

Study Overview
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Brief Summary
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Green tea is being recognized as a beverage with potential benefits for human health and on cognitive function. In vitro and in vivo studies provide preliminary evidence that green tea intake may play a positive role in improving effects on cognitive functions. The investigators aim to examine the neural effects of green tea extract on brain activation in humans.

Detailed Description
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As functional neuroimaging provides a means of examining how green tea extract acts on the brain, we used functional magnetic resonance imaging (fMRI) to study healthy volunteers while they performed a working memory task following intra-gastric administration of either 250 ml or 500 ml Rivella green® (RG), a milk whey based green tea extract containing soft drink, or Rivella blue® (RB), a milk whey based soft drink without green tea extract as sham condition in a double-blind, controlled design. Based on the literature on pharmacological and behavioural effects of green tea, we hypothesized - a priori - that green tea extract would subtly modulate the engagement of the dorsolateral prefrontal cortex (DLPFC), a brain region critically involved in many cognitive functions such as working memory processing. A double-blind, controlled, within-subject study with counterbalanced order of substance administration using an established protocol (6-8) was conducted over 4 sessions (250 ml or 500 ml Rivella green® (including green tea extract; RG), 250 or 500 ml Rivella blue® (RB). Each participant was scanned four times with a one-week interval between scans. The order of substance administration across sessions was counterbalanced across subjects, such that equal numbers followed each substance sequence.

Conditions
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Exploratory Behavior

Intervention / Treatment
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* Dietary Supplement: Single intragastric instillation of 250 ml green tea extract
* Dietary Supplement: Single intragastric instillation of 500 ml green tea extract
* Dietary Supplement: Single intragastric instillation of 250 ml control solution
* Dietary Supplement: Single intragastric instillation of 500 ml control solution


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: right-handed healthy males, no drugs, non-smoking Exclusion Criteria: drug abuse, smoker, left-handed

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 35 Years

Sexes Eligible for Study
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Male

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Green tea extract, 250 ml<br>Single intragastric instillation of 250 ml green tea extract | Dietary Supplement: Single intragastric instillation of 250 ml green tea extract<br>* Intragastric instillation by feeding tube<br>|
| Active Comparator: Green tea extract, 500 ml<br>Intragastric instillation of 500 ml green tea extract solution | Dietary Supplement: Single intragastric instillation of 500 ml green tea extract<br>* Intragastric instillation by feeding tube<br>|
| Placebo Comparator: Control solution, 250 ml<br>Intragastric instillation of 250 ml control solution | Dietary Supplement: Single intragastric instillation of 250 ml control solution<br>* Intragastric instillation by feeding tube<br>|
| Placebo Comparator: Control solution, 500 ml<br>Single intragastric instillation of 500 ml control solution | Dietary Supplement: Single intragastric instillation of 500 ml control solution<br>* Intragastric instillation by feeding tube<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Functional magnetic resonance imaging (fMRI) in healthy volunteers while they performed a working memory task | Whole brain analysis with a cluster-level threshold was followed by an a priori defined region of interest analysis of the dorsolateral prefrontal cortex including a cluster-level threshold and family-wise error adjustment for multiple comparisons. | 0 and 45 min |