Tea Drinking Significantly Reduces Risk of Stroke

Data from nine studies involving 4,378 strokes among 194,965 individuals were pooled.

Results published in the February 19, 2009, online edition of Stroke, a Journal of the American Heart Association, revealed that regardless of their country of origin, individuals consuming at least three cups of tea per day had a 21% lower risk of stroke than those consuming less than one cup per day. The tea could be black or green as long it was from the classical tea plant Camellia sinensis and not an herbal tea.

So far, researchers have failed to identify the compounds in tea responsible for the stroke-reducing effect. Speculation points to the antioxidant epigallocatechin gallate (EGCG) or the amino acid theanine. Theanine is especially interesting, as it is related to glutamine and can cross the blood-brain barrier. Since it can enter the brain, theanine has psychoactive properties. Theanine has been shown to reduce mental and physical stress and produce feelings of relaxation.

"What we saw was that there was a consistency of effect of appreciable magnitude,” said first author Dr. Lenore Arab, professor of biological chemistry at the University of California, Los Angeles. "By drinking three cups of tea a day, the risk of a stroke was reduced by 21%. It did not matter if it was green or black tea. That is why these findings are so exciting. If we can find a way to prevent the stroke, or prevent the damage, that is simple and not toxic, that would be a great advance. We do know that theanine is nearly 100% absorbed. It gets across the blood-brain barrier and it looks a lot like a molecule that is very similar to glutamate, and glutamate release is associated with stroke. It could be that theanine and glutamate compete for the glutamate receptor in the brain.”

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University of California, Los Angeles