Coffee or green tea drinker? Don't put that cup down: Those beverages may lower your stroke risk if they're a regular part of your daily diet.
"This is the first large-scale study to examine the combined effects of both green tea and coffee on stroke risks," Dr. Yoshihiro Kokubo, chief doctor in the department of preventive cardiology at the National Cerebral and Cardiovascular Center in Osaka, Japan, said in a press release. "You may make a small but positive lifestyle change to help lower the risk of stroke by adding daily green tea to your diet."
The study, which was published on Mar. 14 in Stroke: Journal of the American Heart Association, looked at 83,269 Japanese adults between the ages of 45 to 74. They were questioned about their green tea and coffee drinking habits, and researchers looked at their rates of heart disease, strokes and causes of death for about 13 years. Age, sex and lifestyle factors like smoking, alcohol, weight, diet and exercise were factored into the results.
Researchers discovered that people who drank at least one cup of coffee a day lowered their stroke risk by about 20 percent compared to those who drank it rarely. Though early study results showed that drinking two cups of coffee a day increased coronary heart disease rates, the association was mitigated once cigarette smoking was factored in.
Those who drank two to three cups of green tea daily had a 14 percent lower chance of having a stroke compared to rare green tea drinkers. And, those who drank four or more cups a day? They were able to lower their stroke risk by 20 percent. Green tea drinkers were also more likely to exercise than non-drinkers.
Compared to those who rarely drank either beverage, those who drank at least one cup of coffee or two cups of green tea a day had a 32 percent lower chance of having an intracerebral hemorrhage, a type of stroke that occurs when a blood vessel bursts and bleeds inside the brain. Intracerebral hemorrhages account for 13 percent of strokes.
"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."
Dr. Ralph Sacco, a past president of the American Heart Association who was not involved in the study, pointed out to HealthDay that this study cannot for sure prove drinking coffee or tea lowers stroke risk, but just highlights an association.
"Such association studies are still limited in [the] ability to tell whether it is some ingredients in the coffee or tea or some other behavior common to coffee and tea drinkers that is driving the protective effects," he said.
One important thing to note is a cup of coffee or tea in Japan is only six ounces.
Scientists aren't sure why green tea and coffee lower stroke risk, but they believe a compound in green tea called catechins, an antioxidant with an anti-inflammatory, may play a role. Coffee benefits may be due to a chemical called chlorogenic acid, which lowers the chances of developing Type 2 diabetes and as a results cuts stroke risk.
"We welcome this study which suggests that the benefits of antioxidants in coffee and green tea may offset the potential harm from caffeine. The results demonstrate higher consumption of green tea and coffee might reduce the risks for stroke, especially for inter-cerebral hemorrhage. We would like to see further research to understand the underlying biological mechanisms for these findings," Dr. Dale Webb from the U.K.'s Stroke Association told the Telegraph. He was not involved in the study.