The effects of flavanone-rich citrus juice on cognitive function and cerebral blood flow: an acute, randomised, placebo controlled crossover trial in healthy young adults

One plausible mechanism underlying flavonoid-associated cognitive effects is increased cerebral blood flow (CBF). However, behavioural and CBF effects following flavanone-rich juice consumption have not been explored. The aim was to investigate whether consumption of flavanone-rich juice is associated with acute cognitive benefits and increased regional CBF in healthy young adults. An acute, single-blind, randomised crossover design was applied with two 500ml drink conditions; high flavanone (HF; 70.5mg) and an energy, vitamin C matched zero flavanone control. Twenty four healthy young adults aged 18-30 underwent cognitive testing at baseline and two hours post drink consumption. A further sixteen healthy young adults were recruited for fMRI assessment whereby CBF was measured with arterial spin labelling during conscious resting state at baseline, and two and five hours post drink consumption. The HF drink was associated with significantly increased regional perfusion in the inferior and middle right frontal gyrus at two hours relative to baseline and the control drink. In addition, the HF drink was associated with significantly improved performance on the Digit Symbol Substitution Test at two hours relative to baseline and the control drink, but no effects were observed on any other behavioural cognitive tests. These results demonstrate that consumption of flavanone-rich citrus juice in quantities commonly consumed can acutely enhance blood flow to the brain in healthy young adults. However, further work is required to establish a direct causal link between increased cerebral blood flow and enhanced behavioural outcomes following citrus juice ingestion