Effects of Peppermint Oil in Mild-moderate Hypertension.

Effects of Peppermint Oil in Cardiometabolic Outcomes in Participants With Mild-moderate Hypertension.

Cardiovascular and associated hypertensive diseases are the leading health burden and cause of mortality worldwide; therefore, the necessity for effective interventions is paramount. Dietary interventions to improve cardiovascular health are highly sought after as they possess less risk and financial burden than pharmacological drugs. Our previous randomized trial has shown that oral peppermint can improving systolic blood pressure and other cardiovascular/ blood lipids in healthy individuals. However, to date, no research has explored this using a placebo randomized intervention in patients with hypertension.

Therefore, the primary purpose of the proposed investigation is to test the ability of oral peppermint oil supplementation to improve cardiometabolic parameters in participants with mild-moderate hypertension.

Study Overview

• Status: Completed
• Conditions: Hypertension
• Intervention / Treatment: Other: Placebo; Dietary supplement: Peppermint oil

• Study Type: Interventional
• Enrollment (Actual): 40
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United Kingdom
  • Lancashire
    • Preston, Lancashire, United Kingdom, PR4 0PE
      • University of Central Lancashire

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 65 years (Adult, Older Adult)
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

1. Aged from 18-65 years
2. Systolic blood pressure 120 to 139 mmHg
3. Not taking prescribed medicine for blood pressure management
4. have the ability to complete written questionnaires independently
5. Able to provide informed consent

Exclusion Criteria:

1. diagnosed diabetes mellitus
2. known cardiovascular disease or clinically significant cardiovascular comorbidity, including coronary heart disease, symptomatic heart failure, clinically significant arrhythmia, or a history of stroke or transient ischaemic attack within the previous 6 months
3. known or suspected secondary hypertension, including renal, renovascular, or endocrine causes
4. known clinically significant renal impairment or severe hepatic disease
5. evidence or history of severe hypertension related target organ damage requiring specialist management
6. pregnant or lactating women
7. allergy to peppermint
8. habitual consumption of peppermint products
9. regular consumption of antioxidant supplements
10. body mass index larger than 40.0 kg/m²
11. current enrolment in other clinical trials or use of other external therapies likely to influence outcomes
12. condition(s) likely to compromise informed consent, protocol compliance, or outcome assessment, including severe psychiatric illness, cognitive impairment, or active substance or alcohol misuse.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Double

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Placebo Comparator: Placebo; Identical in taste and colour to the supplement juice, but with no peppermint content.	Other: Placebo; Placebo
Experimental: Peppermint oil; 50 uL of peppermint oil, which will be diluted with 100 mL of water - taken twice per day.	Dietary supplement: Peppermint oil; Peppermint oil

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Systolic blood pressure	Systolic blood pressure - measured using a digital blood pressure monitor	Baseline
Systolic blood pressure	Systolic blood pressure - measured using a digital blood pressure monitor	20 days

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Waist circumference	Waist circumference - measured using anthropocentric tape	Baseline
Waist circumference	Waist circumference - measured using anthropocentric tape	20 days
Waist to hip ratio	Ratio of waist to hip circumference - measured using anthropocentric tape	Baseline
Waist to hip ratio	Ratio of waist to hip circumference - measured using anthropocentric tape	20 days
Blood glucose	Capillary blood glucose - mmol/L	Baseline
Blood glucose	Capillary blood glucose - mmol/L	20 days
Blood triglycerides	Capillary blood triglycerides - mmol/L	Baseline
Blood triglycerides	Capillary blood triglycerides - mmol/L	20 days
Blood cholesterol (Total, HDL & LDL)	Capillary blood cholesterol - mmol/L	Baseline
Blood cholesterol (Total, HDL & LDL)	Capillary blood cholesterol - mmol/L	20 days
Triglyceride glucose index	Log transformed measurement of the blood glucose and blood triglyceride measures outlined above.	Baseline
Triglyceride glucose index	Log transformed measurement of the blood glucose and blood triglyceride measures outlined above.	20 days
Coop-Wonka chart	Psychological wellbeing - The Coop-Wonka chart is a six item questionnaire with a 1-5 scoring system for each thus the chart has a maximum score of 30 which indicates the lowest possible psychological Wellbeing.	Baseline
Coop-Wonka chart	Psychological wellbeing - The Coop-Wonka chart is a six item questionnaire with a 1-5 scoring system for each thus the chart has a maximum score of 30 which indicates the lowest possible psychological Wellbeing.	20 days
Beck Depression Inventory	Psychological wellbeing - the Beck Depression Inventory is a 21 questionnaire with questions that range in scoring from 0-3, thus the maximum score is 63 which is the highest depression score possible.	Baseline
Beck Depression Inventory	Psychological wellbeing - the Beck Depression Inventory is a 21 questionnaire with questions that range in scoring from 0-3, thus the maximum score is 63 which is the highest depression score possible.	20 days
State Trait Anxiety Inventory	Psychological wellbeing - the state trait anxiety inventory is a 40 item questionnaire with each question having a 1-4 score system, thus the maximum score is 80 which indicates the highest level of anxiety.	Baseline
State Trait Anxiety Inventory	Psychological wellbeing - the state trait anxiety inventory is a 40 item questionnaire with each question having a 1-4 score system, thus the maximum score is 80 which indicates the highest level of anxiety.	20 days
Insomnia Severity Index	Sleep quality - The Insomnia Severity Index is a brief instrument designed to assess the severity of both nighttime and daytime components of insomnia. The Insomnia Severity Index is a 7-item self-report questionnaire yielding a total score ranging from 0 to 28.	Baseline
Insomnia Severity Index	Sleep quality - The Insomnia Severity Index is a brief instrument designed to assess the severity of both nighttime and daytime components of insomnia. The Insomnia Severity Index is a 7-item self-report questionnaire yielding a total score ranging from 0 to 28.	20 days
Pittsburgh Sleep Quality Index	Sleep quality - The Pittsburgh Sleep Quality index, is a questionnaire that consists of 19 self-rated questions, grouped into 7 components. Each component is scored separately, weighted equally on a 0 - 3 scale and the scores of the 7 components are then added to give a global score, which has a range of 0 - 21 with higher scores indicating worse sleep quality.	Baseline
Pittsburgh Sleep Quality Index	Sleep quality - The Pittsburgh Sleep Quality index, is a questionnaire that consists of 19 self-rated questions, grouped into 7 components. Each component is scored separately, weighted equally on a 0 - 3 scale and the scores of the 7 components are then added to give a global score, which has a range of 0 - 21 with higher scores indicating worse sleep quality.	20 days
Epworth Sleepiness Scale	Sleep quality - The Epworth Sleepiness Scale is a self-administered questionnaire with 8 questions. Respondents are asked to rate, on a 4-point scale (0-3) with a maximum score of 24.	Baseline
Epworth Sleepiness Scale	Sleep quality - The Epworth Sleepiness Scale is a self-administered questionnaire with 8 questions. Respondents are asked to rate, on a 4-point scale (0-3) with a maximum score of 24.	20 days
Diastolic blood pressure	Diastolic blood pressure - measured using a digital blood pressure monitor	Baseline
Diastolic blood pressure	Diastolic blood pressure - measured using a digital blood pressure monitor	20 days
Percent bodyfat and fat mass	Participants percentage composition of fat - measured using bio-electrical impedance	Baseline
Percent bodyfat and fat mass	Participants percentage composition of fat - measured using bio-electrical impedance	20 days
Total and HDL cholesterol ratio	Ratio of total cholesterol to HDL cholesterol	Baseline
Total and HDL cholesterol ratio	Ratio of total cholesterol to HDL cholesterol	20 days
LDL and HDL cholesterol ratio	Ratio of LDL to HDL cholesterol	Baseline
Total and HDL cholesterol ratio	Ratio of LDL to HDL cholesterol	20 days

Collaborators and Investigators

• Sponsor: University of Central Lancashire
• Collaborators: University of Hertfordshire

Publications and helpful links

General Publications

• Sinclair J, Du X, Shadwell G, Dillon S, Butters B, Bottoms L. 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. PLoS One. 2025 May 7;20(5):e0321986. doi: 10.1371/journal.pone.0321986. eCollection 2025.

Study record dates

Study Major Dates

• Study Start (Actual): January 1, 2024
• Primary Completion (Actual): August 1, 2025
• Study Completion (Actual): August 10, 2025

Study Registration Dates

• First Submitted: September 26, 2022
• First Submitted That Met QC Criteria: September 26, 2022
• First Posted (Actual): September 30, 2022

Study Record Updates

• Last Update Posted (Actual): January 15, 2026
• Last Update Submitted That Met QC Criteria: January 13, 2026
• Last Verified: January 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Vascular Diseases; Cardiovascular Diseases; Hypertension; Physiological Effects of Drugs; Antiemetics; Autonomic Agents; Peripheral Nervous System Agents; Gastrointestinal Agents; Parasympatholytics; peppermint oil
• Other Study ID Numbers: Peppermint oil hypertension

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No