Investigating the Effects of Green Tea on Blood Viscosity

December 19, 2024 updated by: Jeremy Paul Edward Spencer, University of Reading

Investigating the Effects of Green Tea on Whole Blood Viscosity

A diet high in flavonoids is becoming more established as beneficial to human health. Recent data suggest that the regular consumption of flavanols can reduce the numbers of deaths by cardiovascular disease at a population level. The mechanisms for these reductions in deaths by cardiovascular disease are still debated and little is known about their impacts on factors affecting blood viscosity. The metabolism of flavanols is complex, with different metabolites being predominant in the blood at different time points. Therefore, in this study, we will investigate the effects of green tea, a well-known source of flavanols, on blood viscosity at different time points. This will be assessed in healthy individuals with no history of cardiovascular disease aged 65+ years old. Blood viscosity will be measured before, and 2hours and 8hours after the consumption of green tea.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Detailed Description

Participants will first be screened via a questionnaire on RedCap. This will include a list of exclusion and inclusion criteria. Examples of what will be included are: must be a non-smoker, no history of CVD or CVD in immediate family, no history of metabolic diseases, no food allergies, or intolerances and not be on any medication for cardiovascular purposes (e.g. aspirin or blood pressure medication).

Before confirmation, a screening visit will be undertaken where checks for regular haematocrit, blood pressure, plasma triglycerides, blood glucose and inflammatory markers and BMI will be taken. This will involve a 4.5 ml blood sample. Additionally, the research nurse will assess the potential participant's veins, and participants who do not have 2 'good' veins for giving blood will be excluded from the trial.

Following recruitment, participants will be asked to follow a set of criteria for the 24 hours prior to participating in the study. This will include, following a low polyphenol diet and not consuming any over the counter medication, caffeine or alcohol for 24 hours prior to participating. Participants will also be asked to attend fasted for 12 hours. Participants will also be asked to not take part in any vigorous/aerobic exercise in the 24 hours leading up to the study.

Following recruitment, and on arrival, participants will be asked to confirm they have followed the requirements for the previous 24 hours and full informed consent will be obtained from the participant. Participants will complete a spot urine test to measure osmolality as a measure of hydration. Participants will be asked to sit in a rested position for 15 min prior to each blood sample. Blood pressure will then be measured followed by a blood sample (17.5ml). The blood sample will be passed through the viscometer to assess whole blood and plasma viscosity and part of the blood sample will be used to measure haematocrit, inflammatory markers and blood lipids. The participant will then be given 200 mL green tea. They will be asked to consume this within 15 minutes. The intervention will be provided in an opaque cup with a lid on and the participant will be asked not to remove the lid so that the contents is not revealed to them. This will be followed by a low flavonoid breakfast. The same blood sample and urine test will then be taken at 2 hours and 8 hours after the start of consuming the drink, and these will be processed in the same way. A low flavonoid meal will also be provided between the 2- and 8-hour blood sample. A second visit will involve the exact same protocol; however, the participants will be given hot water as a control condition.

On the first of two visits, the participant will be asked to fill out a food frequency questionnaire. The order of green tea/control visits will be randomised and counterbalanced. In the 12-hours leading up to the visit, participants will be asked to consume 500 mL of water (a bottle will be provided). Throughout the visit, participants will be provided with unlimited water to drink and the total volume that has been consumed between each blood sample throughout the study will be recorded. On the second visit, the participant will be asked to replicate this amount.

Study Type

Interventional

Enrollment (Estimated)

35

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

Study Locations

  • United Kingdom
      • Reading, United Kingdom
        • Hugh Sinclaire Unit of Human Nutrition, Departmeant of Food and Nutrition, University of Reading
        • Contact:
        • Contact:
          • Jeremy P E Spencer, PhD

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Older Adult

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  • Participants ages 65 years and older
  • Non-smoker Participants with at least 2 'good' veins for giving blood

Exclusion Criteria:

  • Participants under (BMI <18.5 kg/m2) or extremely over-nourished (BMI >30 kg/m2)
  • Participants on prescription medication for CVD or regularly taking blood thinning drugs such as aspirin.
  • Participants with a history of CVD or CVD in immediate family/ high resting blood pressure
  • Participants with any food allergies/intolerances
  • Participants with a history of metabolic diseases/ high resting blood glucose
  • Participants with high resting levels of inflammatory markers (CRP)
  • Participants on hormone replacement therapy
  • Participants with abnormal red blood cell count or low haemoglobin stores

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Prevention
  • Allocation: Randomized
  • Interventional Model: Crossover Assignment
  • Masking: Double

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Green Tea
200 mL green tea on first visit
Dietary supplement: Green Tea
200 mL Green Tea
Dietary supplement: Control (Hot Water)
200 mL hot water
Placebo Comparator: Hot Water
200 mL hot water on first visit
Dietary supplement: Green Tea
200 mL Green Tea
Dietary supplement: Control (Hot Water)
200 mL hot water

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Time Frame
Whole Blood Viscosity
Time Frame: Baseline to 2 hours and 8 hours
Baseline to 2 hours and 8 hours

Secondary Outcome Measures

Outcome Measure
Time Frame
Plasma Viscosity
Time Frame: Baseline to 2 hours and 8 hours
Baseline to 2 hours and 8 hours
Blood Triglycerides
Time Frame: Baseline to 2 hours and 8 hours
Baseline to 2 hours and 8 hours
C-reactive protein
Time Frame: Baseline to 2 hours and 8 hours
Baseline to 2 hours and 8 hours

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

University of Reading

Collaborators

Biotechnology and Biological Sciences Research Council
Royal Berkshire NHS Foundation Trust

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

January 1, 2025

Primary Completion (Estimated)

May 1, 2025

Study Completion (Estimated)

May 1, 2025

Study Registration Dates

First Submitted

December 13, 2024

First Submitted That Met QC Criteria

December 13, 2024

First Posted (Actual)

March 25, 2025

Study Record Updates

Last Update Posted (Actual)

March 25, 2025

Last Update Submitted That Met QC Criteria

December 19, 2024

Last Verified

December 1, 2024

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • UREC 24/22

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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