title: Dietary nitrate modulates cerebral blood flow parameters and cognitive performance in humans: A double-blind, placebo-controlled, crossover investigation.
abstract: Nitrate derived from vegetables is consumed as part of a normal diet and is reduced endogenously via nitrite to nitric oxide. It has been shown to improve endothelial function, reduce blood pressure and the oxygen cost of sub-maximal exercise, and increase regional perfusion in the brain. The current study assessed the effects of dietary nitrate on cognitive performance and prefrontal cortex cerebral blood-flow (CBF) parameters in healthy adults. In this randomised, double-blind, placebo-controlled, parallel-groups study, 40 healthy adults received either placebo or 450 ml beetroot juice (~5.5 mmol nitrate). Following a 90 minute drink/absorption period, participants performed a selection of cognitive tasks that activate the frontal cortex for 54 min. Near-Infrared Spectroscopy (NIRS) was used to monitor CBF and hemodynamics, as indexed by concentration changes in oxygenated and deoxygenated-haemoglobin, in the frontal cortex throughout. The bioconversion of nitrate to nitrite was confirmed in plasma by ozone-based chemi-luminescence. Dietary nitrate modulated the hemodynamic response to task performance, with an initial increase in CBF at the start of the task period, followed by consistent reductions during the least demanding of the three tasks utilised. Cognitive performance was improved on the serial 3s subtraction task. These results show that single doses of dietary nitrate can modulate the CBF response to task performance and potentially improve cognitive performance, and suggest one possible mechanism by which vegetable consumption may have beneficial effects on brain function.
authors.affiliation: Brain, Performance and Nutrition Research Centre, School of Life Sciences, Northumbria University, Newcastle upon Tyne NE1 8ST, United Kingdom.
authors.forename: Emma L
authors.initials: EL
authors.lastname: Wightman
authors.affiliation: Brain, Performance and Nutrition Research Centre, School of Life Sciences, Northumbria University, Newcastle upon Tyne NE1 8ST, United Kingdom.
authors.forename: Crystal F
authors.initials: CF
authors.lastname: Haskell-Ramsay
authors.affiliation: Sport, Exercise and Wellbeing Research Centre, School of Life Sciences, Northumbria University, Newcastle upon Tyne NE1 8ST, United Kingdom.
authors.forename: Kevin G
authors.initials: KG
authors.lastname: Thompson
authors.affiliation: School of Sport and Health Sciences, St. Luke's Campus, University of Exeter, Exeter EX1 2LU, United Kingdom.
authors.forename: Jamie R
authors.initials: JR
authors.lastname: Blackwell
authors.affiliation: Peninsula College of Medicine and Dentistry, St. Luke's Campus, University of Exeter, Exeter EX1 2LU, United Kingdom.
authors.forename: Paul G
authors.initials: PG
authors.lastname: Winyard
authors.affiliation: Brain, Performance and Nutrition Research Centre, School of Life Sciences, Northumbria University, Newcastle upon Tyne NE1 8ST, United Kingdom.
authors.forename: Joanne
authors.initials: J
authors.lastname: Forster
authors.affiliation: School of Sport and Health Sciences, St. Luke's Campus, University of Exeter, Exeter EX1 2LU, United Kingdom.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Jones
authors.affiliation: Brain, Performance and Nutrition Research Centre, School of Life Sciences, Northumbria University, Newcastle upon Tyne NE1 8ST, United Kingdom. Electronic address: david.kennedy@northumbria.ac.uk.
authors.forename: David O
authors.initials: DO
authors.lastname: Kennedy
mesh_terms: D000293:Adolescent; D000328:Adult; D000339:Affect; D000704:Analysis of Variance; D001794:Blood Pressure / Q000502:physiology; D002540:Cerebral Cortex / Q000098:blood supply*; D003071:Cognition / Q000187:drug effects / Q000502:physiology*; D003430:Cross-Sectional Studies; D019587:Dietary Supplements; D004311:Double-Blind Method; D005260:Female; D000067030:Fruit and Vegetable Juices; D006339:Heart Rate / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology*; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests; D009566:Nitrates / Q000008:administration & dosage* / Q000097:blood; D019265:Spectroscopy, Near-Infrared; D055815:Young Adult
chemical_list: D006454:Hemoglobins; D009566:Nitrates
keywords: Beetroot; Cerebral blood flow; Cognition; Near-Infrared Spectroscopy; Nitrate (NO(3)(−)); Nitric oxide; Nitrite (NO(2)(−))