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

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: Completed
• Conditions: Blood Pressure
• Intervention / Treatment: Dietary supplement: Nitrate-depleted beetroot juice plus placebo tablet; Dietary supplement: Beetroot juice plus vitamin C tablet; Dietary supplement: Beetroot juice plus placebo tablet

• Study Type: Interventional
• Enrollment (Actual): 15
• Phase: Not Applicable

Contacts and Locations

Study Locations

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

Participation Criteria

Eligibility Criteria

• 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

How is the study designed?

Design Details

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

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
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

Outcome Measure	Measure Description	Time Frame
Cardiac function	Resting cardiac function using a non-invasive methodology (Finometer)	Pre and post 3 days of supplementation
Blood pressure	Resting diastolic and systolic blood pressure using portable automated monitor	Pre, 24 hours, 48 hours and 72 hours after supplementation

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Flow-mediated dilation	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	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	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	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	A colorimetric assay kit will be used to measure vitamin C in urine samples	Pre and post 3 days supplementation
Urine 8-isoprastane concentration	An Enzyme Linked Immuosorbant assay will be used to determine 8-isoprostane concentrations in urine.	Pre and post 3 days supplementation

Collaborators and Investigators

• Sponsor: University of Nottingham

Publications and helpful links

General Publications

• Deanfield JE, Halcox JP, Rabelink TJ. Endothelial function and dysfunction: testing and clinical relevance. Circulation. 2007 Mar 13;115(10):1285-95. doi: 10.1161/CIRCULATIONAHA.106.652859. No abstract available.
• Forstermann U. Nitric oxide and oxidative stress in vascular disease. Pflugers Arch. 2010 May;459(6):923-39. doi: 10.1007/s00424-010-0808-2. Epub 2010 Mar 21.
• Gori T, Munzel T. Oxidative stress and endothelial dysfunction: therapeutic implications. Ann Med. 2011 Jun;43(4):259-72. doi: 10.3109/07853890.2010.543920. Epub 2011 Feb 1.

Study record dates

Study Major Dates

• Study Start (Actual): November 25, 2024
• Primary Completion (Actual): August 1, 2025
• Study Completion (Actual): August 22, 2025

Study Registration Dates

• First Submitted: December 5, 2024
• First Submitted That Met QC Criteria: November 18, 2025
• First Posted (Estimated): November 21, 2025

Study Record Updates

• Last Update Posted (Actual): December 2, 2025
• Last Update Submitted That Met QC Criteria: November 24, 2025
• Last Verified: November 1, 2025

More Information

Terms related to this study

• Keywords: Cardiovascular disease; Vitamin C; endothelial function; nitrate
• Additional Relevant MeSH Terms: Cardiovascular Diseases; Organic Chemicals; Carbohydrates; Sugar Acids; Acids, Acyclic; Carboxylic Acids; Hydroxy Acids; Ascorbic Acid
• Other Study ID 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