Abstract/Summary

Dietary Flavonoids and Human Cognition: Meta-analyses Background: Dietary flavonoids have been examined for their cognitive benefits with mixed findings. General conclusions over flavonoid efficacy have therefore not been possible. Objectives: to quantitatively examine the effects of flavonoid consumption on cognition. Methods: Flavonoid effects on cognitive performance and associated moderating factors were assessed by meta-analysis of human intervention studies (k=80). Results: Flavonoid consumption was shown to have a significant positive effect on cognition, determined by cognitive health status. Positive effects were found following berry, cocoa or GB supplementation, low and medium doses, in middle-aged and older adults, chronic studies and particularly in long-term memory, processing speed and mood. Conclusions: Flavonoid supplementation may support positive cognitive functioning. ROAB and BEAT trials Background: Significant flavonoid effects were found in older adults and following berry supplementation by meta-analysis. In particular, chronic treatment with wild blueberry extract (WBE) has been shown to improve EM and reduce SBP in older adults. Objectives: ROAB trial: to determine acute WBE effects on cognitive function and whether these are dose and time-dependent. BEAT trial: to replicate alleviation of cognitive decline during a predicted post-lunch dip following WBE 222. Methods: Both studies employed a randomised, double-blind, placebo-controlled, within-subject design to investigate the cognitive and cardiovascular effects of WBE in older adults (68-75 years). In ROAB, 28 participants received WBE doses of 111mg, 222mg, 444mg, 888mg and placebo, with measurements taken at 2 hours, 4 hours and 6 hours post-intervention. In BEAT (n=45), measurements were taken 1 hour after lunch at 14:00 to coincide with the post-lunch dip in cognitive performance. ii Results: ROAB trial: Benefits to EM and EF speed in more cognitively challenging tasks, and alleviation of a post-lunch decline in EF were found. SBP and DBP were significantly reduced following WBE 222. BEAT trial: This showed improved EF speed only. A post-lunch dip was not observed. Conclusions: These studies indicate that acute WBE supplementation may attenuate cognitive decline associated with the post-lunch dip and in keeping with proposed vasodilatory mechanisms, may also reduce BP. Summary: Dietary flavonoids were found to have positive effects on human cognition. Acute WBE showed benefits to EF speed, however EM speed and BP reductions were only apparent under conditions of increased cognitive fatigue, such as the post-lunch dip. Abbreviations: BEAT - Blueberry Extract Acute Trial BP – blood pressure DBP – diastolic blood pressure EF – executive function EM – episodic memory GB – Ginkgo biloba ROAB - Randomised Older Adult Blueberry Trial SBP – systolic blood pressure WBE – wild blueberry extract