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

Not Applicable

Completed

• Conditions: Blood Pressure

• Registration Number: NCT07242066
• Lead Sponsor: University of Nottingham

Brief Summary

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.

Detailed Description

Not available

Study Timeline

• Study Start: 2024-11-25
• Study First Submitted: 2024-12-05
• Primary Completion: 2025-08-01
• Study Completion: 2025-08-22
• Status Verified: 2025-11
• Study First Submitted QC: 2025-11-18
• Last Update Submitted: 2025-11-18
• Study First Posted: 2025-11-21
• Last Update Posted: 2025-11-21

Recruitment & Eligibility

• Status: COMPLETED
• Sex: All
• Target Recruitment: 15

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: 25.0 - 40.0 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 & Design

• Study Type: INTERVENTIONAL
• Study Design: CROSSOVER

Primary Outcome Measures

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

Secondary Outcome Measures

Name	Time	Method
Flow-mediated dilation	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.
Saliva nitrate concentration	Pre and post 3 days supplementation	Colorimetric assays based on the Griess reaction will be used to measure nitrate concentration in saliva samples
Urinary nitrate concentration	Pre and post 3 days supplementation	Colorimetric assays based on the Griess reaction will be used to measure nitrate concentration in urine samples
Saliva nitrite concentration	Pre and post 3 days supplementation	Colorimetric assays based on the Griess reaction will be used to measure nitrite concentration in saliva samples
Urine vitamin C concentration	Pre and post 3 days supplementation	A colorimetric assay kit will be used to measure vitamin C in urine samples
Urine 8-isoprastane concentration	Pre and post 3 days supplementation	An Enzyme Linked Immuosorbant assay will be used to determine 8-isoprostane concentrations in urine.

Trial Locations

Locations (1)

David Greenfield Human Physiology Lab, Queens Medical Centre; 🇬🇧 Nottingham, Nottinghamshire, United Kingdom