A Randomized Placebo-Controlled Clinical Trial Exploring the Short-Term Cognitive and Cerebrovascular Effects of Consuming Peppermint Tea: A Mediation Study.

The cognitive-enhancing effects of peppermint have been widely reported. Vasodilation, causing an increase in cerebral blood flow (CBF) in the prefrontal cortex, has been implicated as a possible mediator. We tested this here. A total of N = 25 individuals, all aged over 18 years, were recruited via convenience sampling. A randomized, single blind placebo-controlled, independent groups design was used to assess whether groups (peppermint vs. placebo control) could be differentiated with respect to change in cognition, assessed via a computerized battery, and change in cerebral blood flow, assessed with Near-Infrared-Spectroscopy (NIRS), from pre-post intervention. Groups disparities in both cognitive and cerebrovascular change scores (from pre-post intervention) emerged. Improvements in cognitive performance were better in the peppermint group. Increases in hemodynamic activity, indexed by Oxygenated (Oxy-Hb) and Total hemoglobin (Total-Hb), were also greater in the peppermint group. Cerebrovascular changes from pre-to post-intervention were unrelated to cognitive changes over the same period, ruling out mediation effects. In conclusion, 200 mL of peppermint, consumed as tea, effectively boosted cognition and cerebral blood flow in otherwise healthy adults. Increased cerebral blood flow, however, did not mediate the cognitive-enhancing effects of peppermint. Future research incorporating larger samples and exploring other neurophysiological mediators is encouraged.