Berry-derived polyphenols found in purple grape juice have been associated with a number of health benefits in humans, including better episodic memory( Reference Kesse-Guyot, Fezeu, Andreeva, Touvier, Scalbert and Hercberg 1 ) and improved endothelial function(see Reference Vislocky and Fernandez 2 for review). Previous intervention studies of Concord grape juice have demonstrated improvement to memory in age-associated mild cognitive impairment following at least 12 weeks supplementation, as well as increased brain activation (assessed with fMRI) following 16 weeks intervention. Anthocyanin-rich berry extracts have also been observed to improve sustained attention when measured acutely in healthy young adults( Reference Watson, Haskell and Scheepens 3 ) but no studies to date have demonstrated acute cognitive effects of grape juice.
This randomised, placebo-controlled, double-blind, balanced-crossover study, assessed the effects of a single dose of 200 ml Concord purple grape juice or sugar and flavour-matched placebo in 20 healthy young adults. Computerised measures of cognition and mood were completed at baseline and following a 20-min absorption period, chosen due to a peak in native anthocyanins at ∼30 minutes post-ingestion.
Following a single serve of Concord purple grape juice, a significant increase in calm ratings (p<0.05) and an improvement in speed of attention (p<0.05) were observed. There were no effects on memory. This supports a previous demonstration of improved sustained attention following berry fruit, possibly implicating this as an anthocyanin effect, which account for 46% of the polyphenolic content of the grape juice administered. However, the phenolic acids, flavanols and flavonols also present are liable to play a role in any neurocognitive effect. These findings in a small sample of healthy young adults suggest that further investigation of the efficacy of purple grape juice in preventing age-associated cognitive decline is warranted to ascertain peak dose effects as well as exploring the active compound(s) responsible for such effects.