Effects of Daily Wild Blueberry Consumption on Cognitive and Vascular Function in Healthy Older Individuals: A Randomized Double Blind Controlled Trial (the Bluflow Study)

Abstract Objectives To investigate the effects of 12-week daily consumption of wild blueberry (poly)phenols on cognitive performance, vascular function, cerebral blood flow and gut microbiome in healthy older individuals. Methods A parallel, double blind, placebo controlled RCT was conducted in 61 healthy individuals, aged 65–80 years. The impact of wild blueberry (poly)phenols on cognition, vascular function (flow-mediated dilation; FMD, and blood pressure; BP), active and resting cerebral blood flow (CBF; using transcranial doppler ultrasound) was assessed. Measurements were taken at baseline and 12-weeks following daily consumption of 26 g freeze-dried blueberry powder containing 260 mg anthocyanins (equivalent to 178 g fresh wild blueberries) or a placebo powder matched for colour, taste, nutrients and fibre. Faecal samples were collected in both visits to measure changes in the gut microbiome using 16s rRNA sequencing. Blood and 24 h urine samples were also collected for the analysis of plasma and urinary (poly)phenol metabolites using LC-MS and authentic standards. Results Linear mixed modelling analysis with baseline performance as a covariate, revealed that accuracy scores for the switching task targeting executive function, significantly improved for the wild blueberry (WBB) group compared to placebo at 12 weeks (F(1,90,12) = 5.13, P = 0.026)). Additionally, immediate recall measure (AVLT) examining short-term recall memory revealed a significant improvement for the WBB compared to placebo at 12 weeks (F(1,46) = 4.321, P = 0.043)). FMD improved by 0.86% (F(1,54) = 32.8, P < 0.001) in the WBB group compared with the placebo group after 12-weeks daily consumption. Systolic 24 h ambulatory BP decreased by −3.59 mmHg (F(1,51) = 4.6, P = 0.037) in the WBB group compared to the placebo group. No changes in active or resting CBF were observed between groups. Conclusions This data suggests that daily consumption of wild blueberries may improve cognitive and vascular function in older adults. The role of circulating (poly)phenol metabolites and the gut microbiome on the effects observed is currently under investigation. Funding Sources Wild Blueberry Association of North America.