Chronic and postprandial effect of blueberries on cognitive function, alertness, and mood in participants with metabolic syndrome – results from a six-month, double-blind, randomized controlled trial

Peter J. Curtis, Vera van der Velpen, Lindsey Berends, Amy Jennings, Laura Haag, Anne-Marie Minihane, Preeti Chandra, Colin D. Kay, Eric B. Rimm, Aedin Cassidy

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Background. Anthocyanin and blueberry intakes positively associate with cognitive function in population-based studies, and cognitive benefits in randomized controlled trials (RCTs) of adults with self-perceived or clinical cognitive dysfunction. To date, adults with metabolic syndrome (MetS), but without cognitive dysfunction, are understudied.

Objective. Cognitive function, mood, alertness, and sleep quality were assessed as secondary endpoints in MetS participants, postprandially (over 24h) and following 6-mo blueberry intake.

Method. A double-blind RCT was conducted, assessing the primary effect of consuming freeze-dried blueberry powder, compared against an iso-caloric placebo, on cardiometabolic health over 6 mo. and a 24h postprandial period (at baseline). In this secondary analysis of the main study, data from those completing mood, alertness, cognition, and sleep assessments are presented (i.e. n=115 in the 6 mo. study, n=33 in the postprandial study), using i) Bond Lader self-rated scores, ii) electronic cognitive battery (i.e. testing attention, working memory, episodic memory, speed of memory retrieval, executive function, picture recognition), and iii) the Leeds Sleep Evaluation Questionnaire. Urinary and serum anthocyanin metabolites were quantified, and apolipoprotein E genotype status determined.

Results. Postprandial self-rated calmness significantly improved after 1 cup blueberries (p=0.01; q=0.04; with an 11.6% improvement compared to baseline between 0 and 24h for the 1 cup group), but all other mood, sleep and cognitive function parameters were unaffected after postprandial and 6-mo blueberries. Across the ½ and 1 cup groups, microbial metabolites of anthocyanins and chlorogenic acid (i.e. hydroxycinnamic acids, benzoic acids, phenylalanine derivatives, hippuric acids) and catechin were associated with favorable chronic and postprandial memory, attention, executive function and calmness.

Conclusions. Whilst self-rated calmness improved postprandially, and significant cognition-metabolite associations were identified, our data did not support strong cognitive, mood, alertness or sleep quality improvements in MetS participants after blueberry intervention.
Original languageEnglish
JournalThe American Journal of Clinical Nutrition
Early online date6 Feb 2024
Publication statusE-pub ahead of print - 6 Feb 2024


  • Cognitive function
  • Metabolic syndrome
  • Blueberry anthocyanins
  • Anthocyanin-derived phenolic acid metabolites

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