Can green tea help to keep blood vessels healthy?
Publication Date:03/07/2008
Research extolling the virtues of green tea is rarely out of the news. Reports from the latest study suggest that this increasingly popular variety of tea might help to keep the blood vessels healthy. We take a closer look at the study.
What do we know already?
Drinking tea on a regular basis has been linked in some studies to a reduced risk of heart disease, although the link is not proven. Researchers think that it's the chemicals called flavonoids in tea that might exert this beneficial effect. Flavonoids act as antioxidants in the body and can prevent some harmful processes in the body. Certain other foods, such as red wine and dark chocolate, are rich in flavonoids, and these too are thought to have a protective effect against heart disease.
If you have heart disease, clumps of fat build up on the lining of your blood vessels. Instead of being smooth these blood vessels become stiffer and narrower, which makes it harder for blood to flow through them. This can lead to high blood pressure. If a fatty deposit gets bigger it can block the blood vessels and cause a heart attack.
Most people in the UK drink black tea, and research has previously suggested that this type of tea may help keep the cells that line the blood vessels healthy. Some studies have suggested that coffee has a similar effect.
The present study was done to find out what effect, if any, green tea has on blood vessels.
What does the new study say?
The new study found that green tea slightly increases a measure of how elastic the blood vessels were. This effect was seen 30 minutes after volunteers drank a large cup of green tea made with 6 grams of green tea. But the blood vessels had returned to their original state 90 minutes after drinking the tea.
The researchers also looked at what happened to the volunteers' blood vessels after they had a drink which contained the amount of caffeine that's found in an ordinary cup of tea and after they drank a cup of hot water. Neither of these two drinks had any effect on the blood vessels.
Where does the study come from?
This study was done by researchers from Athens Medical School in Greece. It was published in a journal called the European Journal of Cardiovascular Prevention and Rehabilitation. The researchers do not say how the study was funded.
How reliable are the findings?
This study involved only 14 volunteers and it only looked at what happened to the blood vessels immediately after drinking green tea. To find out if green tea can really play any part in preventing heart disease, you'd need to compare a large group of people who drank green tea regularly for a long time with another group who did not drink green tea, to see who developed heart disease. No one has done this kind of research yet.
The researchers didn't compare the effects of green tea with black tea or coffee, which might have been useful.
What does this mean for me?
All this study shows is that in healthy people, drinking a cup of green tea seems to make the blood vessels slightly more elastic 30 minutes later, but that this effect disappears after an hour and half. The study was in healthy volunteers with an average age of 30, so we don't know if this happens to older people who drink green tea. We don't know from this study if drinking green regularly for a number of years protects against heart disease.
However, we do know that several other things affect your chances of getting heart disease. Some of the most important are whether heart disease runs in your family, whether you smoke, whether you are overweight, how much you exercise and whether you have other conditions, such as high blood pressure, high cholesterol and diabetes. Your overall diet is also important.
What should I do now?
You can reduce your risk of getting heart disease by following a healthy lifestyle, for example by eating healthily, exercising regularly and not smoking. Treating conditions such as high blood pressure, high cholesterol and diabetes can also reduce your chances of having a heart attack. We can't say for certain yet whether drinking green tea helps keep the blood vessels healthy in the long term, or how it impacts on heart disease. But if you like the taste of green tea, there's certainly no reason not to drink it.
From:
Alexopoulos N, Vlachopoulos C, Aznaouridis K, et al. The acute effect of green tea consumption on endothelial function in healthy individuals. European Journal of Cardiovascular Preventions and Rehabilitation. 2008; 15: 300-305.
To learn more about heart disease see our information on heart attack.
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This information does not replace medical advice. If you are concerned you might have a medical problem please ask your Boots pharmacy team in your local Boots store, or see your doctor.
