Meta Analysis Finds Lower Risk Of Stroke Among Tea Drinkers

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May 26, 2009

Meta-analysis finds lower risk of stroke among tea drinkers

Meta-analysis finds lower risk of strong among tea drinkers

The results of a meta-analysis published in the May 1, 2009 issue of the American Heart Association journal Stroke revealed that men and women who consumed at least three cups of green or black tea per day had a lower risk of stroke than those who consumed less than one cup.

For their review, Lenore Arab, PhD and her colleagues at UCLA's David Geffen School of Medicine selected 9 epidemiological studies that included data on tea intake and fatal or nonfatal stroke outcomes. The studies included a total of 194,965 participants in 6 different countries, among whom 4,378 strokes occurred.

The pooled analysis uncovered a 21 percent lower risk of fatal or nonfatal stroke among those who consumed three or more cups of tea per day compared to those whose intake was reported at less than one cup per day. The findings involved participants from diverse geographical areas and were consistent whether green or black tea was consumed.

Although the analysis did not break down stroke according to type, the authors believe that the association observed is likely to be due primarily to tea's effect on ischemic stroke. In their discussion of possible mechanisms for tea against stroke, they note that although tea's antioxidant and anti-inflammatory actions are frequently cited, green and black tea have also been demonstrated to reduce blood pressure in an experimental model of hypertension, a condition that is a strong risk factor for stroke. Additionally, tea has been shown to enhance endothelial function, which, when reduced, impairs cerebral blood flow. Furthermore, a compound found in tea known as theanine readily crosses into the brain, where it may provide a neuroprotective effect.

"The observational, epidemiological research in humans is strongly supportive of the hypothesis that tea consumption, at the level of greater than or equal to 3 cups per day, either as green or black tea, reduces the risk of occurrence of stroke, stroke volume, and mortality from stroke," the authors conclude.

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Stroke and cerebrovascular disease

There are two main kinds of stroke. The most common, an ischemic stroke, occurs when an artery in the brain is blocked by a blood clot, usually because of atherosclerosis (the deposition of plaque on the inside of artery walls). Alternatively, a hemorrhagic stroke can occur when a portion of the arterial wall weakens and bursts.

Ischemic stroke is responsible for 80 percent of all strokes (NINDS 2005). There are two kinds of ischemic stroke. The first, a thrombotic stroke, results from a blood clot (thrombus) forming in a vessel inside the brain and cutting off the blood supply to the tissues served by that vessel.

The second, an embolic stroke, occurs when a clot forms somewhere else in the body, breaks off, and travels to the brain. The clot can originate in a peripheral artery, in the heart itself, or in the arteries in the neck or brain. Among people with an abnormal heart rhythm called atrial fibrillation, clots can arise in the left atrium and travel through the left side of the heart and the aorta and into the brain. When the clot becomes lodged in the artery, the tissue beyond the blockage is starved of oxygen and begins to die.

Most strokes are caused by blood clots that form as a result of atherosclerosis (Gorelick PB 2002). Once known as “hardening of the arteries,” atherosclerosis occurs when the arteries become clogged with plaque deposits and the structure and function of the inner arterial wall (the endothelium) are compromised. If atherosclerotic plaque deposits become brittle and rupture, blood clots can form that lead to stroke.

Green tea catechins, which are rich in flavonoids, possess powerful antioxidant properties that have been studied in the context of limiting damage due to ischemic stroke. Animal studies have shown that green tea extract limits the size of stroke lesions in a dose-dependent manner when administered immediately after an ischemic episode, leading researchers to suggest that green tea may have promise in the acute treatment of ischemic stroke (Suzuki M et al 2004; Lee SY et al 2003). Another study found that animals that had a high intake of green tea experienced less cerebral damage after a stroke than did their counterparts who weren’t consuming green tea (Hong JT et al 2001).

Prostate Cancer Research Institute (PCRI)
2009 Prostate Cancer Conference

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September 12-13, 2009

The Prostate Cancer Conference 2009

The Prostate Cancer Research Institute (PCRI) mission is to improve the quality of men’s lives by supporting research and disseminating information that educates and empowers patients, families and the medical community. PCRI is pleased to announce the 11th major conference devoted to prostate cancer, planned and/or produced by members of The Prostate Cancer Research Institute. As in the past, this conference will provide insight for patients, caregivers and medical professionals.

Moderated by the highly regarded Dr. Mark Moyad and Dr. Mark Scholz, this year’s conference will again focus on quality of life Issues. Faculty will talk about important lifestyle and health issues including diet and dietary supplements, erectile dysfunction, hormone blockade side effects and other current issues relating to advanced disease. Exciting up-and-coming technology and research will also be presented.

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