Green Tea and Stroke Studies
Pathways To Recovery

Four green tea and stroke studies suggest how green tea may prevent and treat strokes.



Study #1:
Curtin University 2007 Review

Does drinking green tea reduce your risk of getting a stroke ? Dr. Fraser from the Curtin University of Technology investigated in his 2007 literature review.

According to him, two green tea and stroke population studies reported positive findings. A large number of studies have also proposed biological mechanisms on how consuming tea may reduce stroke risk.

But results have been inconsistent. Interpreting them is tricky. Populations can respond differently to tea drinking. The types of tea, how long it is being consumed and the types of stroke can sway the results either way.

Further studies are needed, but It is no point waiting for the scientists to prove it. Dr. Fraser concluded:

Green tea … consumption should be encouraged because it could potentially serve as a practical method for stroke prevention.

Green tea not only reduces stroke risk, it may one day be used to reverse cell damage after a stroke has occurred.

Green Tea and Stroke Study #2:
UCLA's School of Medicine 2009 Analysis

According to findings from a recent meta-analysis, drinking 3 or more cups of tea a day may help to reduce the risk of stroke and death from stroke by 21%.

The purpose of this green tea and stroke study was to thoroughly examine the human clinical and epidemiological data available to determine whether black or green tea, as a hot beverage, has an impact on the risk of stroke in humans.

Ten studies from 6 countries were included in the final meta-analysis: China, Japan, Finland, Netherlands, Australia and the US. These studies included 7 populations that drank primarily or exclusively black tea and 3 that drank primarily green tea.

The pooled meta-analyses show tea consumption to be associated with a reduced risk for occurrence of and mortality from stroke.

Subjects drinking 3 or more cups of tea per day appear to reduce their risk of a fatal or non-fatal stroke by around 21% compared with non-tea drinkers. This effect was observed across all the 6 countries studied despite different drinking customs.

A further meta-analysis was also conducted in 5 sub-groups to see if associations relating to the type of tea consumed (green or black) or ethnicity had any further effect. Results from these sub-group analyses showed similar results to the over-all risk reduction, meaning that the effect does not appear to be specific to black or green tea, or to Asian or non-Asian populations.

Being a review of observational studies, the mechanism by which tea may protect against stroke remains speculative. Whilst antioxidant function and anti-inflammatory actions are popular theories, other mechanisms may include beneficial effects on blood pressure and endothelial function, as well as the neuroprotective action of theanine.

The authors suggest that their findings may be one of the most actionable lifestyle changes to significantly reduce the risk of stroke.

Green Tea and Stroke Study #3:
Gallotannin (GT) Rescue Brain

Another 2007 study conducted by the University of California-San Francisco reported similar benefit, but through a different mechanism.

Researchers found that green tea extract gallotannin (called GT) can protect against post-ischemic brain damage. It does so by inhibiting the action of PARG, an enzyme that kills brain cells by inhibiting cell repair.

The researchers have previously found that GT inhibits PARG in cells culture. Now they have found the same benefits apply to laboratory rats. 

Green tea extract GT was administered intranasally – via the nose – up to 3 hours after reperfusion.

They also discovered that GT helps stroke patients in another way. It blocks movement of a protein called apoptosis inducing factor (AIF). This protein resides in a dormant state, but when activated can cause cell death.

Green Tea and Stroke Study #4:
EGCG Regenerate Organ Cells

A 2005 study conducted by the Institute of Child Health in the United Kingdom found that drinking green tea after a stroke may speed up the recovery process.

Heart attacks reduce the amount of oxygen and nutrients reaching the brain and heart, causing cell death and irreversible damage.

Laboratory testing on heart cells found that green tea contains an active compound called EGCG (epigallocatechin gallate) that reduces cell death after a heart attack or stroke.

EGCG also speeds up the recovery of heart cells and alleviates organ damage. It works by blocking the action of a protein called Stat 1, which plays a part in inducing cell death.

"We're extremely encouraged by these findings and hope to implement them in the clinical setting to minimize cell death activation levels in patients with acute coronary artery disease," said molecular biologist Dr. Anastasis Stephanou, who led the research.

He said more green tea and stroke research would have to be carried out before patients could be advised to drink it after a heart attack or stroke.

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References

Fraser ML, Mok GS, Lee AH (2007). Green tea and stroke prevention: Emerging evidence. Complement Ther Med. 2007 Mar;15(1):46-53. Epub 2006 Aug 30.

Arab, L., Liu, W. and Elashoff, D. (2009). Green and black tea consumption and risk of stroke. A meta-analysis. Stroke, DOI:10.1161/STROKEAHA.108.538470.

Paul A. Townsend, Tiziano M. Scarabelli, Evasio Pasini, Gianluca Gitti, Marta Menegazzi, Hisanori Suzuki, Richard A. Knight, David S. Latchman, and Anastasis Stephanou (2005). Epigallocatechin-3-gallate inhibits STAT-1 activation and protects cardiac myocytes from ischemia/reperfusion-induced apoptosis. The FASEB Journal Express Article doi:10.1096/fj.04-1716fje.

Media Release http://pub.ucsf.edu/newsservices/releases/200612283.

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