Background: Animal experiments document effects of grape juice on cognitive performance and motor skills, and observational studies in humans suggest an inverse association between flavonoid intake and cognitive decline. These effects may be related to the antioxidant properties of polyphenols. Juice consumption and flavonoid intake may also affect appetite. Objective: To study the acute effects of grape juice consumption on appetite, mood and implicit memory during a time of increased lethargy - the post-lunch dip. Design: Thirty-five participants with a mean age of 26 years who smoked a mean of 11 cigarettes/day for 8 years were included in the study. It included a practice session and two treatment sessions. All sessions involved consumption of grape juice or an energy-matched placebo with lunch followed by assessments of mood, implicit memory, appetite and food intake. Results: Mood decreased over time for both treatments, but there were no differences after lunch between grape juice and placebo for any measure. Conclusion: This study did not document any acute effects of grape juice consumption on mood, implicit memory, appetite or food intake in smokers.
grape juice; polyphenols; appetite; implicit memory; post-lunch dip
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