Effects of peppermint (Mentha piperita L.) oil in cardiometabolic outcomes in participants with pre and stage 1 hypertension: Protocol for a placebo randomized controlled trial

BACKGROUND: Hypertension is the predominant risk factor for cardiovascular disease morbidity and mortality, with significant healthcare utilization and expenditure. Pharmaceutical management is habitually adopted; although its long-term effectiveness remains ambiguous, and accompanying adverse effects are disquieting. Peppermint owing to its abundance of menthol and flavonoids, possesses a range of potential hypertensive benefits. RATIONALE: Our previous trial has shown that peppermint is able to mediate significant improvements in systolic blood pressure in healthy individuals. But there has yet to be any randomized placebo-controlled studies, examining the efficacy of peppermint supplementation in hypertensive individuals. OBJECTIVE: This study proposes a placebo randomized controlled trial, exploring the effects of daily peppermint oil supplementation on outcomes pertinent to hypertensive disease in individuals with pre and stage 1 hypertension. METHODS AND ANALYSES: This 20-day, parallel randomized, placebo-controlled trial will recruit 40 individuals, assigned to receive either 100μL per day of either Peppermint oil or a peppermint flavoured placebo. The primary trial outcome will be the between-group difference in systolic blood pressure from baseline to post-intervention. Secondary outcome measurements will be between-group differences in anthropometric, haematological, diastolic blood pressure/ resting heart rate, psychological wellbeing, and sleep efficacy indices. Statistical analysis will be conducted on an intention-to-treat basis using linear mixed effects models to contrast differences in the changes from baseline to 20-days between the two trial arms. ETHICS AND DISSEMINATION: Ethical approval has been granted by the University of Central Lancashire (HEALTH 01074) and the study has formally been registered as a trial (NCT05561543). Dissemination of the trial findings will be through publication in a peer-reviewed journal. TRIAL REGISTRATION: ClinicalTrials.gov NCT05561543. ETHICS: HEALTH 01074.