A small clinical trial has found that a twice-daily dose of peppermint oil modestly lowered systolic blood pressure in adults with mildly elevated readings, a result researchers call encouraging but preliminary given the study's size and short duration.
The trial, led by Dr. Jonnie Sinclair, a reader in sport and health sciences at the University of Lancashire in England, randomly assigned 40 adults ages 18 to 65 with prehypertension or stage 1 hypertension to take either 100 microliters of peppermint oil or a peppermint-flavored placebo twice a day for 20 days, following a protocol the team had registered in advance. Neither participants nor researchers knew who received the active oil until the trial ended. The results were published in PLOS One.
A modest but consistent drop
By the end of the 20-day period, the peppermint oil group's average systolic blood pressure — the top number in a reading — had fallen by 8.5 millimeters of mercury, while the placebo group showed no meaningful change. Participants taking the oil also had lower resting heart rates. Diastolic blood pressure, body measurements, blood test results, mood and sleep quality showed no significant differences between the two groups.
Peppermint's most abundant compound, menthol, is known from laboratory research to relax smooth muscle in blood vessel walls, and the researchers suggest that effect could partly account for the drop in systolic pressure, though the trial did not directly test the mechanism and the authors say more work is needed to confirm how the oil acts in the body.
Peppermint oil is low in calories and price so it's proved to be a very simple and cost-effective solution to potentially treat millions of people around the world.
Dr. Jonnie Sinclair, University of Lancashire
Sinclair noted that conventional blood pressure medications, while effective, do not suit every patient equally. "It's not always clear how well they work in the long-term, and they can cause unwanted side effects," he said, suggesting a low-cost dietary option could complement, rather than replace, existing treatment for people with mild, early-stage hypertension.
The trial's limitations are notable: with just 40 participants at a single site over only 20 days, the findings do not establish whether the effect persists, whether it would hold in people with more severe hypertension, or whether peppermint oil is safe to combine with blood pressure medications. Like much early-stage nutrition and supplement research, the results will need to be replicated in larger, longer trials before peppermint oil could be recommended as a treatment.
