A new study coming from scientists at UCLA has found that drinking at least three cups of green or black tea a day can significantly reduce the risk of stroke. Interestingly, the more you drink, the better your odds of holding back that stroke.
The study was published in the online edition of Stroke: Journal of the American Heart Association, were presented Feb. 19 at the American Heart Association's annual International Stroke Conference in San Diego, Calif.
The UCLA researchers examined nine studies describing 4,378 strokes among nearly 195,000 individuals, according to lead author Dr. Lenore Arab, a professor of medicine in the division of general internal medicine and health services research at the David Geffen School of Medicine at UCLA.
"What we saw was that there was a consistency of effect of appreciable magnitude. By drinking three cups of tea a day, the risk of a stroke was reduced by 21 percent. It didn't matter if it was green or black tea," said Dr. Arab. Oddly, the data shows this effect appears to be linear. For instance, if one drinks three cups a day, the risk falls by 21 percent; follow that with another three cups and the risk drops another 21 percent.
Note that this effect was found in tea made from the plant Camellia sinensis, both green and black varieties, and not from the many popular types of herbal teas on the market.
To date, there are very few known ways to reduce the risk of stroke. Developing medications for stroke victims is particularly challenging, given that the drug has to get to the stroke-damaged site quickly because damage occurs so fast. Arab said that by the time a stroke victim gets medical care, it's nearly too late to impede the damage.
"That's why these findings are so exciting," she said. "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."
Researchers have speculated that the antioxidant epigallocatechin gallate (EGCG) or the amino acid theanine may be what helps. Theanine is nearly 100-percent absorbed, Arab said. "It gets across the blood-brain barrier and it looks a lot like a molecule that's 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."
Although a randomized clinical trial is needed to confirm this effect, the findings suggest that drinking three cups of green or black tea a day could help prevent an ischemic stroke.