Vascular Function
Conditions
Keywords
Flow mediated dilation, tea, blood pressure
Brief summary
Research indicate that people who regularly drink tea have a reduced risk of stroke or heart disease. In a number of studies in which people that normally do not drink showed that their blood vessels function improved when the drunk tea. The current study tests whether a specific black tea improves vessel function in non-tea drinking hypertensive subjects.
Detailed description
Epidemiological studies indicate that regular consumption of three cups of black tea per day reduces the risk of stroke or myocardial infarction. In a number of previous nutrition intervention studies tea has been shown to improve vascular function as assessed by Flow Mediated Dilation in various populations. The current confirmatory study tests a specific black tea against a placebo in a population of in non-tea drinking hypertensive subjects.
Interventions
OTHERTea
Single dose of black tea infusion containing approximately 400 mg flavonoids (expressed as gallic acid equivalents) with added sugar.
OTHERPlacebo
Placebo: tea flavour, colouring and sugar
Sponsors
King's College London
Unilever R&D
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Masking
QUADRUPLE (Subject, Caregiver, Investigator, Outcomes Assessor)
Eligibility
Sex/Gender
ALL
Age
18 Years to 65 Years
Healthy volunteers
No
Inclusion criteria
* Males and post menopausal (\> 1 year) females, not on hormone replacement therapy * Aged \>18 and \< 65 years * Body mass index (BMI) of \>=18.0 and =\<35.0 kg/m2 * Hypertension as previously diagnosed by primary care or hospital physician. * If untreated, office BP between 140/90 mmHg and 160/100 mmHg on screening * If treated, a controlled blood pressure (\<160/100) on stable medication for at least 4 weeks
Exclusion criteria
* Tea drinkers: having typically consumed \> 1 cup of black tea per week. * Current smoker or has stopped smoking less than 6 months before start of study * Self reported alcohol intake of \>21 units/week * Established cardiovascular disease other than hypertension * Clinically significant arrhythmia * Diabetes mellitus * Chronic Kidney Disease \> stage 2 * 10-year cardiovascular risk equivalent to 20% or greater using the QRisk2 calculator * Abnormality of laboratory blood tests considered clinically significant * Any other significant intercurrent condition/disease
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Flow Mediated Dilation | Before and 2 hours after test product intake | Flow mediated dilation (FMD) of the brachial artery was measured using vascular ultra sound and automated edge detection software: * 1 minute baseline scan to measure the baseline diameter of artery * 5 minutes of forearm occlusion at 250±30 mmHg, below the elbow (2-5 cm from antecubital crease) * 4 minutes FMD scan, which started immediately after release of occlusion Percentage FMD was calculated as the maximum increase in diameter after cuff release relative to the baseline diameter |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Endothelium-independent Vasodilation | 2.5 hours after test product intake | Endothelium-independent dilation after glyceryl trinitrate defined as maximal percent increase in diameter |
| Systolic Blood Pressure Supine | Before and 110 minutes after test product intake | Systolic blood pressure measured while lying down |
| Diastolic Blood Pressure Supine | Before and 110 minutes after test product intake | Diastolic blood pressure measured while lying down |
| Systolic Blood Pressure Sitting | Before and 90 minutes after test product intake | Systolic blood pressure measured while sitting |
| Diastolic Blood Pressure Sitting | Before and 90 minutes after test product intake | Diastolic blood pressure measured while sitting |
Countries
United Kingdom
Participant flow
Recruitment details
53 subjects were screened between August 2014 and and October 2015
Pre-assignment details
All 30 subjects meeting the inclusion criteria were randomised
Participants by arm
| Arm | Count |
|---|---|
| All Study Participants Participants who were randomised to either receive Tea first followed by Placebo or Placebo first followed by Tea | 30 |
| Total | 30 |
Baseline characteristics
| Characteristic | All Study Participants |
|---|---|
| Age, Continuous | 53 years |
| Body Mass Index | 26.3 kg/m^2 |
| Diastolic blood pressure | 92 mmHg |
| Gender Female | 7 Participants |
| Gender Male | 23 Participants |
| Systolic blood pressure | 145 mmHg |
Adverse events
| Event type | EG000 affected / at risk | EG001 affected / at risk |
|---|---|---|
| deaths Total, all-cause mortality | — / — | — / — |
| other Total, other adverse events | 1 / 30 | 1 / 30 |
| serious Total, serious adverse events | 0 / 30 | 0 / 30 |
Outcome results
Primary
Flow Mediated Dilation
Flow mediated dilation (FMD) of the brachial artery was measured using vascular ultra sound and automated edge detection software: * 1 minute baseline scan to measure the baseline diameter of artery * 5 minutes of forearm occlusion at 250±30 mmHg, below the elbow (2-5 cm from antecubital crease) * 4 minutes FMD scan, which started immediately after release of occlusion Percentage FMD was calculated as the maximum increase in diameter after cuff release relative to the baseline diameter
Time frame: Before and 2 hours after test product intake
Population: All participants who received at least one dose of each intervention and completed all study visits
| Arm | Measure | Group | Value (LEAST_SQUARES_MEAN) | Dispersion |
|---|---|---|---|---|
| Tea Beverage | Flow Mediated Dilation | FMD before test product intake | 5.24 percentage of change in diameter | Standard Deviation 2.42 |
| Tea Beverage | Flow Mediated Dilation | FMD two hours after test product intake | 6.05 percentage of change in diameter | Standard Deviation 2.33 |
| Placebo Beverage | Flow Mediated Dilation | FMD before test product intake | 5.02 percentage of change in diameter | Standard Deviation 2.14 |
| Placebo Beverage | Flow Mediated Dilation | FMD two hours after test product intake | 5.74 percentage of change in diameter | Standard Deviation 2.66 |
Comparison: Estimated effect of tea vs placebop-value: 0.430.23% CI: [-0.37, 0.83]Mixed Models Analysis
Secondary
Diastolic Blood Pressure Sitting
Diastolic blood pressure measured while sitting
Time frame: Before and 90 minutes after test product intake
Population: All participants who received at least one dose of each intervention and completed all study visits
| Arm | Measure | Group | Value (LEAST_SQUARES_MEAN) | Dispersion |
|---|---|---|---|---|
| Tea Beverage | Diastolic Blood Pressure Sitting | Before test product intake | 86.1 mmHg | Standard Deviation 10.3 |
| Tea Beverage | Diastolic Blood Pressure Sitting | After test product intake | 90.7 mmHg | Standard Deviation 10.5 |
| Placebo Beverage | Diastolic Blood Pressure Sitting | Before test product intake | 87.7 mmHg | Standard Deviation 10.5 |
| Placebo Beverage | Diastolic Blood Pressure Sitting | After test product intake | 89.4 mmHg | Standard Deviation 10 |
95% CI: [-0.73, 4.09]Mixed Models Analysis
Secondary
Diastolic Blood Pressure Supine
Diastolic blood pressure measured while lying down
Time frame: Before and 110 minutes after test product intake
Population: All participants who received at least one dose of each intervention and completed all study visits
| Arm | Measure | Group | Value (LEAST_SQUARES_MEAN) | Dispersion |
|---|---|---|---|---|
| Tea Beverage | Diastolic Blood Pressure Supine | Before test product intake | 85.1 mmHg | Standard Deviation 10.2 |
| Tea Beverage | Diastolic Blood Pressure Supine | After test product intake | 88.9 mmHg | Standard Deviation 10.9 |
| Placebo Beverage | Diastolic Blood Pressure Supine | Before test product intake | 85.7 mmHg | Standard Deviation 10.2 |
| Placebo Beverage | Diastolic Blood Pressure Supine | After test product intake | 89.5 mmHg | Standard Deviation 10.5 |
95% CI: [-2.16, 1.37]Mixed Models Analysis
Secondary
Endothelium-independent Vasodilation
Endothelium-independent dilation after glyceryl trinitrate defined as maximal percent increase in diameter
Time frame: 2.5 hours after test product intake
Population: All participants who received at least one dose of each intervention and completed all study visits
| Arm | Measure | Value (LEAST_SQUARES_MEAN) |
|---|---|---|
| Tea Beverage | Endothelium-independent Vasodilation | 12.1 percentage of change in diameter |
| Placebo Beverage | Endothelium-independent Vasodilation | 11.4 percentage of change in diameter |
Comparison: Estimated effect of tea vs. placebop-value: 0.295% CI: [-0.4, 1.82]Mixed Models Analysis
Secondary
Systolic Blood Pressure Sitting
Systolic blood pressure measured while sitting
Time frame: Before and 90 minutes after test product intake
Population: All participants who received at least one dose of each intervention and completed all study visits
| Arm | Measure | Group | Value (LEAST_SQUARES_MEAN) | Dispersion |
|---|---|---|---|---|
| Tea Beverage | Systolic Blood Pressure Sitting | Before test product intake | 134.7 mmHg | Standard Deviation 13.7 |
| Tea Beverage | Systolic Blood Pressure Sitting | After test product intake | 146.4 mmHg | Standard Deviation 13.1 |
| Placebo Beverage | Systolic Blood Pressure Sitting | Before test product intake | 137.2 mmHg | Standard Deviation 13.8 |
| Placebo Beverage | Systolic Blood Pressure Sitting | After test product intake | 148.5 mmHg | Standard Deviation 15 |
95% CI: [-4.65, 0.87]Mixed Models Analysis
Secondary
Systolic Blood Pressure Supine
Systolic blood pressure measured while lying down
Time frame: Before and 110 minutes after test product intake
Population: All participants who received at least one dose of each intervention and completed all study visits
| Arm | Measure | Group | Value (LEAST_SQUARES_MEAN) | Dispersion |
|---|---|---|---|---|
| Tea Beverage | Systolic Blood Pressure Supine | Before test product intake | 135.5 mmHg | Standard Deviation 14.2 |
| Tea Beverage | Systolic Blood Pressure Supine | After test product intake | 145.0 mmHg | Standard Deviation 16.2 |
| Placebo Beverage | Systolic Blood Pressure Supine | Before test product intake | 138.1 mmHg | Standard Deviation 14 |
| Placebo Beverage | Systolic Blood Pressure Supine | After test product intake | 147.2 mmHg | Standard Deviation 15.7 |
95% CI: [-5.26, 2.55]Mixed Models Analysis