Green tea, coffee may help lower stroke risk
Green tea and coffee may help lower your risk of having a stroke, especially when both are a regular part of your diet, according to research published in Stroke: Journal of the American Heart Association.
"This is the first large-scale study to examine the combined effects of both green tea and coffee on stroke risks," said Yoshihiro Kokubo, M.D., Ph.D., F.A.H.A., F.A.C.C., F.E.S.C., lead author of the study at Japan's National Cerebral and Cardiovascular Center. "You may make a small but positive lifestyle change to help lower the risk of stroke by adding daily green tea to your diet."
Researchers asked 83,269 Japanese adults about their green tea and coffee drinking habits, following them for an average 13 years. They found that the more green tea or coffee people drink, the lower their stroke risks.
- People who drank at least one cup of coffee daily had about a 20 percent lower risk of stroke compared to those who rarely drank it.
- People who drank two to three cups of green tea daily had a 14 percent lower risk of stroke and those who had at least four cups had a 20 percent lower risk, compared to those who rarely drank it.
- People who drank at least one cup of coffee or two cups of green tea daily had a 32 percent lower risk of intracerebral hemorrhage, compared to those who rarely drank either beverage. (Intracerebral hemorrhage happens when a blood vessel bursts and bleeds inside the brain. About 13 percent of strokes are hemorrhagic.)
Participants in the study were 45 to 74 years old, almost evenly divided in gender, and were free from cancer and cardiovascular disease.
During the 13-years of follow-up, researchers reviewed participants' hospital medical records and death certificates, collecting data about heart disease, strokes and causes of death. They adjusted their findings to account for age, sex and lifestyle factors like smoking, alcohol, weight, diet and exercise.
Green tea drinkers in the study were more likely to exercise compared to non-drinkers.
Previous limited research has shown green tea's link to lower death risks from heart disease, but has only touched on its association with lower stroke risks. Other studies have shown inconsistent connections between coffee and stroke risks.
Initial study results showed that drinking more than two cups of coffee daily was linked to increasing coronary heart disease rates in age- and sex-adjusted analysis. But researchers didn't find the association after factoring in the effects of cigarette smoking — underscoring smoking's negative health impact on heart and stroke health.
A typical cup of coffee or tea in Japan was approximately six ounces. "However, our self-reported data may be reasonably accurate, because nationwide annual health screenings produced similar results, and our validation study showed relatively high validity." Kokubo said. "The regular action of drinking tea, coffee, largely benefits cardiovascular health because it partly keeps blood clots from forming."
Tea and coffee are the most popular drinks in the world after water, suggesting that these results may apply in America and other countries.
It's unclear how green tea affects stroke risks. A compound group known as catechins may provide some protection. Catechins have an antioxidant anti-inflammatory effect, increasing plasma antioxidant capacity and anti-thrombogenic effects.
Some chemicals in coffee include chlorogenic acid, thus cutting stroke risks by lowering the chances of developing type 2 diabetes. Further research could clarify how the interaction between coffee and green tea might help further lower stroke risks, Kokubo said.
High and moderate consumption of tea are linked with reduced heart disease
High and moderate consumption of tea are linked with reduced heart disease, according to a study published in Arteriosclerosis, Thrombosis, and Vascular Biology: Journal of the American Heart Association.
Researchers in The Netherlands found:
- Drinking more than six cups of tea per day was associated with a 36 percent lower risk of heart disease compared to those who drank less than one cup of tea per day.
- Drinking three to six cups of tea per day was associated with a 45 percent reduced risk of death from heart disease, compared to consumption of less than one cup per day.
Green, black tea can reduce stroke risk
Drinking at least three cups of green or black tea a day can significantly reduce the risk of stroke, a new UCLA study has found. And the more you drink, the better your odds of staving off a stroke.
The study results, published in the online edition of Stroke: Journal of the American Heart Association, were presented Feb. 19, 2009 at the American Heart Association's annual International Stroke Conference in San Diego, Calif.
The UCLA researchers conducted an evidence-based review of all human observational studies on stroke and tea consumption found in the PubMed and Web of Science archives. They found nine studies describing 4,378 strokes among nearly 195,000 individuals, according to lead author 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," said Arab, who is also a professor of biological chemistry. "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."
And extrapolating from the data, the effect appears to be linear, Arab said. 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. This effect was found in tea made from the plant Camellia sinensis, not from herbal teas.
There are very few known ways to reduce the risk of stroke, Arab said. And 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. Though no one is certain which compounds in tea are responsible for this effect, researchers have speculated that the antioxidant epigallocatechin gallate (EGCG) or the amino acid theanine may be what helps. Antioxidants are believed to help prevent coronary artery disease.
"And we do know that 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," she added.
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.
