Not yet recruitingNAINTERVENTIONAL

Investigating the Effects of Green Tea on Blood Viscosity

This study, called 'Investigating the Effects of Green Tea on Blood Viscosity,' is exploring how drinking green tea might affect the thickness of your blood. We already know that certain plant compounds, found in foods like green tea, can be good for your health and might help reduce the risk of heart diseases. However, scientists don't fully understand *how* these compounds work in the body, especially when it comes to blood thickness. This research aims to find out if green tea can change how thick your blood is over a few hours. This is important because blood that's too thick can make it harder for your heart to pump and can increase your risk of heart problems. The study will involve healthy individuals aged 65 and older and will compare the effects of green tea to just drinking hot water.

At a glance

Status

Not yet recruiting

Phase

Sponsor

University of Reading

Enrolment target

Start

01 Jan 2025

Estimated completion

01 May 2025

Cardiovascular Disease

What is this study about?

This research wants to understand if drinking green tea can affect how thick your blood is. You might have heard that eating foods rich in 'flavonoids' (special plant compounds) is good for you. Scientists have noticed that people who regularly consume these compounds tend to have a lower risk of heart and blood vessel diseases. However, we don't fully know all the ways these compounds help protect our hearts.

Blood thickness, also known as blood viscosity, is important because if your blood is too thick, your heart has to work harder to pump it around your body. This can put strain on your heart and increase your risk of various heart-related issues. Green tea is a great source of these helpful plant compounds. This study will carefully look at how green tea impacts blood thickness at different times after you drink it, to see if there's a positive effect. They will compare these results to drinking regular hot water to see if green tea makes a real difference.

The study will involve healthy individuals who are 65 years old or older and do not have any history of heart or blood vessel problems. By understanding how green tea affects blood thickness, researchers hope to learn more about how these plant compounds might help keep our hearts healthy as we get older.

Key takeaways

Study looks at how green tea affects blood thickness.
Aimed at healthy people aged 65 and over.
Compares green tea to just drinking hot water.
Requires blood samples to measure changes.
Helps understand potential heart health benefits of green tea.
Participants must follow specific diet/activity rules before the study day.

Who may be eligible?

To join this study, you need to be 65 years old or older and generally healthy. You also need to be a non-smoker and have at least two veins in your arms that are suitable for taking blood samples. This is important because blood samples will be taken several times during the study.

There are several reasons why you might not be able to join. For example, if you are very underweight or very overweight (with a BMI outside certain limits), if you are taking medication for heart conditions or blood thinning drugs like aspirin, or if you have a history of heart disease yourself or in your immediate family. Also, if you have high blood pressure, diabetes, certain metabolic diseases, or high levels of inflammation, you might not be eligible.

Additionally, if you have any food allergies or intolerances, are on hormone replacement therapy, or have abnormal red blood cell counts or low iron stores (haemoglobin), you would not be able to take part. These checks are put in place to make sure the study is safe for you and that the results are as clear as possible.

Quick self-check

Are you 65 years old or older?
Are you a non-smoker?
Are you free from heart disease, diabetes, or other major metabolic conditions?
Are you not taking medicines for heart conditions or blood thinning drugs (like regular aspirin)?
Are you generally healthy, with a BMI not too low or too high?
Do you have good veins for giving blood samples?

This is a guide only — the research team will confirm whether you can take part.

What does participation involve?

If you decide to take part, you'll first complete a health questionnaire to see if you meet the initial requirements. Then, you'll have a screening visit where a nurse will check your blood pressure, measure your height and weight (BMI), and take a small blood sample (about 4.5ml, or roughly a teaspoon) to check for things like blood sugar and cholesterol. They'll also make sure you have suitable veins for future blood tests.

If you're accepted into the study, you'll be asked to prepare for 24 hours before your main study visit. This means avoiding certain foods (a 'low polyphenol diet'), not taking any over-the-counter medicines, caffeine, or alcohol. You'll also need to fast (not eat anything) for 12 hours before the visit and avoid any strenuous exercise. On the day of the study, you'll confirm you've followed these rules, give your full consent, and provide a small urine sample to check your hydration.

During the study visit, you'll have your blood pressure checked and several blood samples will be taken (each 17.5ml, about 3.5 teaspoons) to measure blood thickness and other factors. You'll sit quietly for 15 minutes before each blood sample is taken. They will be measuring your blood before you drink anything (either green tea or hot water) and then again 2 hours and 8 hours after you drink it. The entire study visit will last for a portion of a day.

Potential risks and benefits

Taking part in any research study has potential benefits and risks. A potential benefit of this study is contributing to our understanding of how green tea might help support heart health as we age. You won't personally receive medical advice or treatment from this study, but your participation helps scientists gather important information. The main risks involved are related to giving blood samples, which can sometimes cause slight bruising, tenderness, or a brief feeling of dizziness. There's also the time commitment involved and the specific diet and activity restrictions you'll need to follow. Remember, your participation is completely voluntary, and you have the right to withdraw from the study at any time without giving a reason, and this will not affect your usual medical care.

Locations (1)

Hugh Sinclaire Unit of Human Nutrition, Departmeant of Food and Nutrition, University of Reading
Reading, United Kingdom

Common questions

What is 'blood viscosity'?

Blood viscosity simply means how thick or sticky your blood is. Thicker blood makes the heart work harder.

Will I know if I receive green tea or just hot water?

The study design usually means you won't know if you're getting green tea or hot water until after the study is over. This helps make the results fairer.

Do I need to buy my own green tea?

No, the study will provide all the green tea (or hot water) needed as part of your participation.

How many times will I have to come to the study centre?

After an initial screening visit, the main study itself will involve one day's visit where you'll have multiple blood samples taken.

What happens if my blood tests show something unexpected?

While the study focuses on research, if any serious abnormalities are found in your screening blood tests they would be communicated to you and your GP.

How to find out more

Jeremy P E Spencer, PhD

j.p.e.spencer@reading.ac.uk +44 (0) 118 378 8724 Official trial record

Always speak to your GP or specialist before deciding to take part in a study.