Inorganic nitrate intake, cognitive function and cerebral blood flow: an updated systematic review and meta-analysis

Authors:
Preprint
Publisher website
Google Scholar
Abstract
Inorganic nitrate, reduced in vivo to nitric oxide via the nitrate-nitrite pathway, has been proposed to influence brain health through vasoactive and neurovascular mechanisms. A 2019 meta-analysis found no effect of nitrate supplementation on cognition or cerebral blood flow, but evidence was then limited to small, short trials in healthy adults. We updated this systematic review, searching MEDLINE, Embase and PsycINFO to June 2026, and extended it to observational studies of habitual dietary nitrate intake. Two reviewers independently screened studies, extracted data and assessed risk of bias (RoB 2; ROBINS-E). Standardised mean differences from 22 randomised trials were pooled in random-effects models; supplementation did not improve cognition (14 trials, 383 participants; SMD 0.100, 95% CI -0.023 to 0.224), resting cerebral blood flow (9 trials; SMD 0.102, 95% CI -0.161 to 0.364) or stimulated cerebral blood flow (6 trials; SMD 0.226, 95% CI -0.064 to 0.516). Seven observational studies could not be pooled, but all five prospective cohorts reported associations favouring higher habitual nitrate intake for brain health outcomes. These findings confirm the earlier null trial result; small, short, underpowered trials and heterogeneous but promising cohort evidence leave open whether dietary nitrate benefits brain health.