An interventional study of Peppermint Oil and Placebo in Pre-metabolic Syndrome, sponsored by University of Central Lancashire. Completed at 1 site in United Kingdom. Open to participants aged 18 Years to 65 Years. Per ClinicalTrials.gov, last updated 2026-09-11.
Sponsored by University of Central Lancashire · Not applicable, Interventional, and Treatment
Cardiovascular and metabolic diseases are leading causes of morbidity and mortality worldwide; therefore, the development of effective preventive interventions is paramount. Pre-metabolic syndrome, characterised by the presence of cardiometabolic risk factors without meeting the full diagnostic criteria for metabolic syndrome, may represent an important opportunity for early intervention. Dietary interventions are particularly attractive because they may carry fewer risks and impose a lower financial burden than pharmacological treatments. Our previous randomised trial showed that oral peppermint oil supplementation improved systolic blood pressure and selected blood lipid parameters in healthy adults. However, no placebo-controlled randomised trial has examined the effects of peppermint oil supplementation in adults with pre-metabolic syndrome.
Therefore, the primary purpose of the proposed investigation is to determine whether oral peppermint oil supplementation improves cardiometabolic parameters in adults with pre-metabolic syndrome.
Aged 18-65 years. Meet two of the five metabolic syndrome criteria. Not taking prescribed medication specifically intended to manage blood pressure, blood glucose or blood lipids.
Able to complete written questionnaires independently. Able to provide informed consent.
Exclusion Criteria:
Diagnosed diabetes mellitus. 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 six months.
Known or suspected secondary hypertension, including renal, renovascular or endocrine causes.
Known clinically significant renal impairment or severe hepatic disease. Evidence or history of hypertension-related target-organ damage requiring specialist management.
Pregnant or lactating. Allergy or known intolerance to peppermint or any ingredient contained in the intervention or placebo.
Habitual consumption of peppermint products. Regular consumption of antioxidant or other dietary supplements likely to influence cardiometabolic outcomes.
Body mass index greater than 40.0 kg/m². Current enrolment in another clinical trial or use of another intervention or therapy likely to influence the study outcomes.
Any condition likely to compromise informed consent, protocol compliance or outcome assessment, including severe psychiatric illness, cognitive impairment, or active substance or alcohol misuse.
50 uL of peppermint oil, which will be diluted with 100 mL of water - taken twice per day.
Dietary Supplement: Peppermint Oil
Identical in taste and colour to the supplement juice, but with no peppermint content.
Radiation: Placebo
50 uL of peppermint oil, which will be diluted with 100 mL of water - taken twice per day.
Identical in taste and colour to the supplement juice, but with no peppermint content.
Systolic blood pressure
Systolic blood pressure - measured using a digital blood pressure monitor
Time frame: Baseline
Systolic blood pressure
Systolic blood pressure - measured using a digital blood pressure monitor
Time frame: 20 days
Diastolic blood pressure
Diastolic blood pressure - measured using a digital blood pressure monitor
Time frame: Baseline
Diastolic blood pressure
Diastolic blood pressure - measured using a digital blood pressure monitor
Time frame: 20 days
Percent bodyfat and fat mass
Participants percentage composition of fat - measured using bio-electrical impedance
Time frame: Baseline
Percent bodyfat and fat mass
Participants percentage composition of fat - measured using bio-electrical impedance
Time frame: 20 days
Waist circumference
Waist circumference - measured using anthropocentric tape
Time frame: Baseline
Waist circumference
Waist circumference - measured using anthropocentric tape
Time frame: 20 days
Waist to hip ratio
Ratio of waist to hip circumference - measured using anthropocentric tape
Time frame: Baseline
Waist to hip ratio
Ratio of waist to hip circumference - measured using anthropocentric tape
Time frame: 20 days
Blood glucose
Capillary blood glucose - mmol/L
Time frame: Baseline
Blood glucose
Capillary blood glucose - mmol/L
Time frame: 20 days
Blood triglycerides
Capillary blood triglycerides - mmol/L
Time frame: Baseline
Blood triglycerides
Capillary blood triglycerides - mmol/L
Time frame: 20 days
Blood cholesterol (Total, HDL & LDL)
Capillary blood cholesterol - mmol/L
Time frame: Baseline
Blood cholesterol (Total, HDL & LDL)
Capillary blood cholesterol - mmol/L
Time frame: 20 days
Total and HDL cholesterol ratio
Ratio of total cholesterol to HDL cholesterol
Time frame: Baseline
Total and HDL cholesterol ratio
Ratio of total cholesterol to HDL cholesterol
Time frame: 20 days
LDL and HDL cholesterol ratio
Ratio of LDL to HDL cholesterol
Time frame: Baseline
LDL and HDL cholesterol ratio
Ratio of LDL to HDL cholesterol
Time frame: 20 days
Triglyceride glucose index
Log transformed measurement of the blood glucose and blood triglyceride measures outlined above.
Time frame: Baseline
Triglyceride glucose index
Log transformed measurement of the blood glucose and blood triglyceride measures outlined above.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 20 days
Plan to share: No
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University of Central Lancashire