A meta-analysis of research studies focused on stroke and tea consumption for human subjects indicated that drinking three cups of green or black tea per day could reduce the risk of ischemic stroke by 20 percent. Data from nine studies covering 4,378 strokes and over 190,000 human subjects were analyzed. (This meta-analysis was conducted in 2009, but it is the most recent one concerning tea and stroke). The meta-analysis was conducted at UCLA. One of the researchers, Lenore Arab, PhD., was generous enough to answer some questions about their study.
What is your opinion on the potential effectiveness of green extract in pill form vs. drinking green tea?
All the research showing an effect is on tea as it is drunk- not as the pills. So I would not trust that the same effect would be seen in that form and those doses.
If I had a 1/5 chance of developing a stroke based on family history, could drinking green tea every day erase that 1/5 chance?
The probability is at the group level- just as with smoking and cancer. And the individual risk is influenced by other things that one does (such as body weight, physical activity, salt consumption). So, just like with other ‘risks’ you are less likely to get hit by a car if you wait for the light to change, it is not a guarantee.
Do you suspect that the impact on endothelial function is 100 percent strengthening blood vessels, or is it also maintaining their elasticity?
We really do not yet know how this works exactly- but we do know that it probably works through a nitrous oxide pathway, and that enhances the ability of the vessel to ‘bounce back’ into shape after being stretched.
Could green tea also reduce brain damage caused by a stroke? Are there any studies about this benefit?
There are animal studies of stroke where every animal gets an induced stroke but some get tea beforehand and others do not. And those studies show that the brain damage (infarction volume) can be reduced by 50 percent with tea.
Is the risk of stroke decreased even more by drinking 6 cups per day, or taking the equivalent in the extract form? Six cups sounds like a lot for most people.
Actually, the cup of tea is quite small, people drink the equivalent of six cups in one or two grande or venti coffees. In fact, there are cultures that do drink many small cups throughout the day.
Is there any indication that the effect of green tea is cumulative, for example, if one began drinking green tea every day at the age of 20 until the senior period, would that be more beneficial than starting to drink it at age 50?
We wish we knew the answer to this, it may be one effect on blood pressure and blood vessels and another on the brain. Animal studies suggest that for the infarction volume long term exposure is not needed. You just have to make sure you have drunk tea within a few hours prior to your stroke. But there is likely also benefit from keeping your blood vessels elastic.
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