Lee Swanson Research Update

Find Time for Tea to Slash Chance of Stroke

March 2009

Drinking three or more cups of green or black tea a day may reduce the risk of stroke by 21%. And the more you drink, the greater the cuts in stroke risk, according to a meta-analysis of nine studies involving 4,378 strokes among 194,965 individuals.

"What we saw was that there was a consistency of effect of appreciable magnitude,” said lead author Lenore Arab. "By drinking three cups of tea a day, the risk of stroke was reduced by 21%. It didn’t matter if it was green or black tea.”

The study was published in the journal Stroke, and the findings were also presented at the American Heart Association’s annual International Stroke Conference in San Diego, CA.

Green tea contains between 30% and 40% of water-extractable polyphenols, while black tea (green tea that has been oxidized by fermentation) contains between 3% and 10%.

The four primary polyphenols found in fresh tea leaves are epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG) and epicatechin (EC).

Arab and her co-workers pooled data from the nine studies, all of which reported stroke occurrence and tea consumption in humans. Compared to people who drank less than a cup of tea a day, drinking three cups a day was associated with a 21% reduction in the risk of stroke.

The researchers also report a linear association with another three cups reducing the risk by another 21%.

No one is certain which compounds in tea are responsible for these potential effects, said Arab. Some researchers have suggested that EGCG or the amino acid theanine may be responsible.

Stroke Published online ahead of print.

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