Effects of Dietary Nitrate and Vitamin C Co-supplementation on Blood Pressure and Endothelial Function in Overweight Individuals

November 24, 2025 updated by: Kostas Tsintzas, University of Nottingham
The investigators have shown in two short-term studies in healthy, young participants that the combined supplementation of inorganic nitrate with vitamin C has beneficial effects on blood pressure and blood vessel wall stiffness. However, the effects of the combined supplementation have not been tested in individuals at greater cardiovascular disease risk. The investigators would like to show whether inorganic nitrate and vitamin C will produce greater effects on blood pressure and endothelial function when compared to inorganic nitrate alone versus the placebo treatment in people at greater risk of cardiovascular disease.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Completed

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Actual)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
15

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • United Kingdom
    • Nottinghamshire
      • Nottingham, Nottinghamshire, United Kingdom, NG7 2UH
        • David Greenfield Human Physiology Lab, Queens Medical Centre

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  • Participant is willing and able to give informed consent for participation in the study.
  • Participant is willing and able to comply with the requirements of the study protocol.
  • Non-smoking men and women.
  • Aged between 50-75 years.
  • Overweight and obese (BMI: over 25.0 kg/m2).

Exclusion Criteria:

  • Having taken part in a research study in the last 3 months involving invasive procedures or an inconvenience allowance.
  • Vegetarian.
  • Smoking.
  • Resting systolic blood pressure greater than 160 mmHg; diastolic blood pressure greater than 100 mmHg.
  • Active cancer and any diagnosis of malignant cancer in the last 5 years.
  • Excessive alcohol intake (>21 units per week).
  • Allergy or intolerance to the intervention food (Beetroot juice).
  • Diagnosis of chronic or acute metabolic and inflammatory conditions that may interfere with the study outcomes.
  • Major surgical operations.
  • Use of prescribed psychiatric drugs (antidepressants, sedatives, antipsychotics), diuretics, organic nitrates, statins and proton pump inhibitors.
  • Use of prescribed hormonal therapies (oestrogens, thyroxin, and progesterone), anti-hypertensive (Calcium++ channel blockers, beta-blockers, and angiotensin-converting-enzyme (ACE) inhibitors), only if the prescription had started, or the dose had been started/changed, in the previous three months.
  • Non-prescribed dietary supplements if not stopped at least for 2 weeks before starting the trial.
  • Use of the mouthwash during the study was not allowed as it interferes with the conversion of oral nitrate into nitrite.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Basic Science
  • Allocation: Randomized
  • Interventional Model: Crossover Assignment
  • Masking: Double

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Placebo Comparator: Placebo
Placebo beetroot juice and tablet
Dietary supplement: Nitrate-depleted beetroot juice plus placebo tablet
nitrate-depleted beetroot juice (70ml in the morning and 70 ml in the evening) plus placebo tablets (containing 500 mg of the non-nutritive sweetener aspartame)
Experimental: Beetroot juice + Vitamin C
Beetroot juice and Vitamin C
Dietary supplement: Beetroot juice plus vitamin C tablet
Concentrated beetroot juice (70 ml in the morning before breakfast and 70 ml in the evening before dinner) plus Vitamin C tablets (500mg/tablet)
Experimental: Beetroot juice + placebo
Beetroot juice + placebo tablet
Dietary supplement: Beetroot juice plus placebo tablet
Concentrated beetroot juice (70ml in the morning and 70 ml in the evening) plus placebo tablets (containing 500 mg of the non-nutritive sweetener aspartame)

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Cardiac function
Time Frame: Pre and post 3 days of supplementation
Resting cardiac function using a non-invasive methodology (Finometer)
Pre and post 3 days of supplementation
Blood pressure
Time Frame: Pre, 24 hours, 48 hours and 72 hours after supplementation
Resting diastolic and systolic blood pressure using portable automated monitor
Pre, 24 hours, 48 hours and 72 hours after supplementation

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Flow-mediated dilation
Time Frame: Pre and post 3 days of supplementation
Assess endothelial function through changes in brachial artery diameter in response to reactive hyperaemia using high-resolution B-mode ultrasound.
Pre and post 3 days of supplementation
Saliva nitrate concentration
Time Frame: Pre and post 3 days supplementation
Colorimetric assays based on the Griess reaction will be used to measure nitrate concentration in saliva samples
Pre and post 3 days supplementation
Urinary nitrate concentration
Time Frame: Pre and post 3 days supplementation
Colorimetric assays based on the Griess reaction will be used to measure nitrate concentration in urine samples
Pre and post 3 days supplementation
Saliva nitrite concentration
Time Frame: Pre and post 3 days supplementation
Colorimetric assays based on the Griess reaction will be used to measure nitrite concentration in saliva samples
Pre and post 3 days supplementation
Urine vitamin C concentration
Time Frame: Pre and post 3 days supplementation
A colorimetric assay kit will be used to measure vitamin C in urine samples
Pre and post 3 days supplementation
Urine 8-isoprastane concentration
Time Frame: Pre and post 3 days supplementation
An Enzyme Linked Immuosorbant assay will be used to determine 8-isoprostane concentrations in urine.
Pre and post 3 days supplementation

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
University of Nottingham

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
November 25, 2024

Primary Completion (Actual)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
August 1, 2025

Study Completion (Actual)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
August 22, 2025

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
December 5, 2024

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
November 18, 2025

First Posted (Estimated)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
November 21, 2025

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
December 2, 2025

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
November 24, 2025

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
November 1, 2025

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • FHMS 128-0224

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

UNDECIDED

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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