07/20/2026
A randomised placebo-controlled trial examined whether peppermint oil could improve blood pressure and related cardiometabolic outcomes in adults with pre- and stage 1 hypertension. Forty participants were randomised to receive either peppermint oil (50 μL (about one drop) twice daily diluted in water; total 100 μL/day) or a peppermint-flavoured placebo for 20 days. The primary endpoint was systolic blood pressure (SBP), with secondary outcomes including diastolic BP, resting heart rate, anthropometry, lipids, glucose, psychological wellbeing and sleep indices.
The main finding was a statistically and clinically meaningful reduction in blood pressure in the peppermint group. Adjusted systolic BP fell by 8.48 mmHg versus placebo (p=0.005; effect size d=−0.94), while diastolic BP fell by −4.57 mmHg (p=0.043) and resting heart rate by −8.92 bpm (p=0.041). Mean SBP in the peppermint arm dropped from 130.1 to 122.0 mmHg over only 20 days, whereas the placebo group remained essentially unchanged. These are surprisingly large effect sizes for such a brief low dose herbal intervention, particularly given that many lifestyle interventions struggle to produce an 8 mmHg SBP reduction in three weeks.
Mechanistically, the authors speculate that menthol-mediated activation of TRPM8 receptors. TRPM8 receptors (Transient Receptor Potential Melastatin 8 channels) are temperature- and chemical-sensitive ion channels. Activated by cool temperatures and compounds such as menthol, they allow calcium and sodium ions to enter cells, generating sensory and physiological signalling responses. TRPM8 receptors are expressed in vascular tissue, autonomic sensory nerves, the gastrointestinal tract and parts of the nervous system, where they appear to play broader regulatory roles. In blood vessels, TRPM8 activation may promote vasodilation through endothelial calcium signalling, nitric oxide production and relaxation of vascular smooth muscle, while also potentially influencing autonomic balance by enhancing parasympathetic activity and reducing sympathetic tone. From a broader systems perspective, TRPM8 receptors can be viewed as environmental and phytochemical sensing channels that help integrate thermal perception, vascular tone, autonomic regulation and protective reflexes. Peppermint’s physiological effects likely extend beyond simple flavour or sensory stimulation into these wider neurovascular signalling networks.
Assessed biochemical parameters, including total cholesterol, LDL cholesterol, HDL cholesterol, triglycerides, glucose and the triglyceride-glucose index, were not significantly altered by peppermint treatment compared with placebo.
The study had several strengths. It was preregistered, placebo-controlled and reasonably well blinded, with only 47% correctly guessing allocation, suggesting the placebo strategy was effective. Compliance was high (93%), attrition was very low, and dietary intake appeared stable between groups. The investigators also appropriately used baseline-adjusted regression models and intention-to-treat analysis with imputation for missing data.
However, several limitations temper the study’s findings. First, this was a very small pilot-style study (n=40, effectively n=38 completers), meaning the impressive effect sizes may partly reflect random variation, or exaggerated small-study effects. The confidence intervals were relatively wide. Second, the intervention duration was short at only 20 days. Blood pressure is inherently variable, and short-term reductions do not necessarily translate into durable antihypertensive effects. The authors themselves also acknowledged that longer studies with ambulatory blood pressure monitoring are needed. On that last point, the study used standard clinic-style BP measurements rather than 24-hour ambulatory monitoring, which is now considered more robust in hypertension research because it reduces white-coat effects and day-to-day variability.
Overall, this is an intriguing and surprisingly positive proof-of-concept study suggesting peppermint oil may have genuine vascular and/or autonomic effects capable of significantly lowering blood pressure in mild hypertension. The effect size is large enough to warrant further investigation and is certainly biologically plausible. One wonders what the impact on BP might be from higher doses, for example of peppermint oil capsules (enteric-coated to reduce the risk of gastro-oesophageal reflux). These are readily available as treatments for irritable bowel syndrome and typically contain 0.2 to 0.4 mL per capsule.
These findings also raise the intriguing possibility that peppermint oil may exert broader physiological effects beyond simple vasodilation, potentially helping to moderate aspects of “sympathetic dominance” through TRPM8-mediated influences on vascular tone and autonomic balance.
For more information see:
https://pubmed.ncbi.nlm.nih.gov/42024666/
https://www.lancashire.ac.uk/news/peppermint-oil-blood-pressure
