Green tea and coffee may lower risk of stroke, especially when both are regularly consumed, according to research published by researchers at Japan's National Cerebral and Cardiovascular Center.
The study authors asked 83,269 Japanese adults about their green tea and coffee drinking habits, following them for an average of 13 years. The participants were 45 to 74 years old, almost evenly male and female, without any reported cancer or heart disease.
In this study, 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.
Similarly, those 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 is when a blood vessel bursts and bleeds inside the brain. About 13 percent of all strokes are hemorrhagic.)
During the 13 years of follow-up period, researchers reviewed participants' hospital medical records and death certificates and collected data about heart disease, strokes and causes of death. Next, they adjusted their findings to account for age, sex and lifestyle factors like smoking, alcohol, weight, diet and exercise.
They found that green tea drinkers in the study were more likely to exercise compared to non-drinkers.
It's not completely clear how green tea affects stroke risk. Compounds in green tea known as catechins - which have antioxidant anti-inflammatory properties, along with increasing plasma antioxidant capacity and anti-thrombogenic actions - may offer protection from stroke.
Chemicals in coffee beneficial for health include chlorogenic acid, which is believed to lower stroke risk by reducing the development of type 2 diabetes.
Previous research has shown an association between green tea and lower stroke risk; while other studies have only shown inconsistent links between coffee and stroke risk.
Clearly, further research is needed to understand exactly how coffee and green tea interact with each other to affect the risk for stroke.