Flow Mediated Dilation in Response to Black Tea

Not Applicable

Completed

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.

Recruitment & Eligibility

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

Arm && Interventions

Group	Intervention	Description
Placebo	Placebo	Placebo
Tea	Tea	Black tea

Primary Outcome Measures

Name	Time	Method
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 Outcome Measures

Name	Time	Method
Systolic Blood Pressure Supine	Before and 110 minutes after test product intake	Systolic 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
Diastolic Blood Pressure Supine	Before and 110 minutes after test product intake	Diastolic blood pressure measured while lying down
Endothelium-independent Vasodilation	2.5 hours after test product intake	Endothelium-independent dilation after glyceryl trinitrate defined as maximal percent increase in diameter