Flow Mediated Dilation in Response to Black Tea

Study Overview
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Brief Summary
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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
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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.

Official Title
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Flow Mediated Dilation in Response to Consumption of Black Tea Versus Artificial Tea, in Non-tea Drinking Hypertensive Subjects.

Conditions
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Vascular Function

Intervention / Treatment
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* Other: Tea
* Other: Placebo


Participation Criteria
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Eligibility Criteria
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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

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 65 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Quadruple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Tea<br>Black tea | Other: Tea<br>* Single dose of black tea infusion containing approximately 400 mg flavonoids (expressed as gallic acid equivalents) with added sugar.<br>|
| Placebo Comparator: Placebo<br>Placebo | Other: Placebo<br>* Placebo: tea flavour, colouring and sugar<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| 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 | Before and 2 hours after test product intake | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Endothelium-independent Vasodilation | Endothelium-independent dilation after glyceryl trinitrate defined as maximal percent increase in diameter | 2.5 hours after test product intake | 
| Systolic Blood Pressure Supine | Systolic blood pressure measured while lying down | Before and 110 minutes after test product intake | 
| Diastolic Blood Pressure Supine | Diastolic blood pressure measured while lying down | Before and 110 minutes after test product intake | 
| Systolic Blood Pressure Sitting | Systolic blood pressure measured while sitting | Before and 90 minutes after test product intake | 
| Diastolic Blood Pressure Sitting | Diastolic blood pressure measured while sitting | Before and 90 minutes after test product intake | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Flow mediated dilation, tea, blood pressure