A single dose of beetroot juice can improve brain blood-flow and potentially improve cognitive performance.
In a clinical study, 40 healthy adults received either placebo or 450 ml beetroot juice. Following a 90-minute drink/absorption period, participants performed a selection of cognitive tasks that activate the frontal cortex for 54 minutes. The results show that single doses of dietary nitrate can modulate the cerebral blood-flow response to task performance and potentially improve cognitive performance.
Reference:
Wightman, E.L., et. al. (2015). Dietary nitrate modulates cerebral blood flow parameters and cognitive performance in humans: A double-blind, placebo-controlled, crossover investigation. Physiology & Behavior, vol. 149, 149-158.