Tea and Forearm Blood Flow

Study Overview
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Brief Summary
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The study will explore the benefit of tea for microcirculation. Subjects will consume tea ar a placebo matched for taste and appearance in a blinded cross over design.

Detailed Description
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Epidemiological studies indicate that regular consumption of black tea reduces the risk of cardiovascular diseases. Tea consumption can result in improvements in endothelial function of conduit arteries as measured by flow mediated dilation. Less is known however about its effects in other vascular beds. The study will test the hypothesis that tea affects endothelial function in the muscle microcirculation. This will be done by assessment of forearm blood flow using venous occlusion plethysmography after consumption of black tea against or placebo in a randomised, full cross-over study in 20 healthy middle-aged to elderly subjects

Official Title
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Forearm Blood Flow Response to Acute Consumption of Black Tea

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 years) females Aged ≥ 45 and ≤ 75 years Body mass index (BMI) of ≥ 18.0 and ≤ 35.0 kg/m2 Judged to be in good health on the basis of medical history, physical examination and routine laboratory tests (total cholesterol, HDL cholesterol, LDL cholesterol, triglycerides, glucose, highly sensitive C-reactive protein). Normal blood coagulation as assessed by routine lab tests Exclusion Criteria: Strenuous exercise > 2 hours per week. Strenuous exercise is defined as exercise which induces sweating and causes sufficient breathlessness to limit conversation 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 or clinically significant arrhythmia Diabetes mellitus Blood pressure > 160/100 mmHg Taking medication that might affect endothelial function (as judged by the PI)

Ages Eligible for Study
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Minimum Age: 45 Years
Maximum Age: 75 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Quadruple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Black tea<br>Approximately 400 mg total polyphenols in 240 ml hot water (loading dose; 2 hours before the start of measurements; t=0) and 130 mg total polyphenols in 120 ml hot water (maintenance dose just before start of the measurements; t=120 min) | Other: Tea<br>* Black tea infusion equivalent to approximately 530 mg total polyphenols expressed as gallic acid equivalents<br>|
| Placebo Comparator: Placebo<br>Caramel colour, maltodextrin and tea flavour in 240 ml hot water (2 hours before the start of measurements; t=0) and 120 ml hot water (maintenance dose just before start of the measurements; t=120 min) | Other: Placebo<br>* Placebo matched to tea with respect to taste and appearance<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Forearm blood flow response to acetylcholine | Does tea ingestion change mean forearm blood flow response to acetylcholine when compared to placebo | During acetylcholine infusion 120-140 min after first tea/placebo intake | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Forearm blood flow response to sodium nitropusside | Does tea ingestion change mean forearm blood flow response to sodium nitropusside when compared to placebo | During sodium nitropusside infusion 170-190 min after first tea/placebo intake | 
| Forearm blood flow response to L-NMMA | Does tea ingestion change mean forearm blood flow response to L-NG-monomethyl Arginine (L-NMMA) when compared to placebo | During L-NMMA infusion 220-240 min after first tea/placebo intake |