Green Tea, Coffee May Guard Against Stroke

Megan Brooks

April 03, 2013

Green tea and coffee consumption may help protect against stroke, according to a large Japanese population-based study.

The study showed that people who drank green tea or coffee regularly had about a 20% lower risk for stroke than their peers who seldom drank these beverages.

"This is the first large-scale study to examine the combined effects of both green tea and coffee on stroke risks," Yoshihiro Kokubo, MD, PhD, head of the Department of Preventive Cardiology, National Cerebral and Cardiovascular Center in Osaka, said in a statement.

Their findings were published online March 14 in Stroke.

Inverse Link

The study involved 82,369 Japanese adults aged 45 to 65 years without cardiovascular disease or cancer at baseline who were followed for a mean of 13 years. "Green tea and coffee consumption was assessed by self-administered food-frequency questionnaire at baseline," Dr. Kokubo told Medscape Medical News.

During more than 1 million person-years of follow-up, the researchers documented 3425 strokes (1964 cerebral infarctions, 1001 intracerebral hemorrhages, and 460 subarachnoid hemorrhages) and 910 coronary heart disease (CHD) events (489 definite myocardial infarctions and 28 sudden cardiac deaths).

In multivariate analysis, higher coffee and green tea consumption were inversely associated with risk for cardiovascular disease (CVD) and stroke.

For example, people who drank at least 1 cup of coffee daily had a 20% lower risk for any stroke (adjusted hazard ratio [aHR], 0.80; 95% confidence interval [CI], 0.72 - 0.90) compared with those who seldom drank coffee.

People who drank 2 to 3 cups of green tea daily had a 14% lower risk for any stroke (aHR, 0.86; 95% CI, 0.78 - 0.95), and those who consumed at least 4 cups had a 20% lower risk (aHR, 0.80; 95% CI, 0.73 - 0.89), compared with those who seldom drank green tea.

The risk reduction for intracerebral hemorrhage was 17% (aHR, 0.83; 95% CI, 0.68 - 1.02) with consumption of at least 1 cup of coffee daily and 23% (aHR, 0.77; 95% CI, 0.63 - 0.92) for 2 cups of green tea daily compared with rare consumption of either beverage.

There was no significant association between coffee and tea consumption and CHD, largely mirroring findings from other studies.

Experts Weigh In

Victoria J. Burley, PhD, senior lecturer in nutritional epidemiology, School of Food Science and Nutrition, University of Leeds, United Kingdom, who wasn't involved in the study, called it "very interesting."

She noted that "both high-fiber foods and these particular beverages may have anti-inflammatory properties. Whole grains, fruit and vegetables, and these beverages are all rich in polyphenols, which appear to have multiple potential actions on markers of CVD risk: blood pressure, glucose homeostasis, lipid metabolism, and so on."

"This appears to be a well-conducted study," Dr. Burley said, "with good power (plenty of cases), with long follow-up and a respectable method of assessing green tea and coffee intake (for these dietary aspects I think an FFQ [food-frequency questionnaire] is likely the best approach)."

She cautioned, however, that the intakes of green tea in this Japanese cohort "far exceed" usual consumption in western populations and that, conversely, intakes of coffee may generally be somewhat lower in Japan.

"The highest coffee intake category was 2-3 cups per day, which is not particularly high. Other studies (eg, conducted in Sweden) have reported elevated CVD risk in people with much higher intakes ( > 7 cups per day), so in setting their highest category this low these study authors may not have been able to pick up evidence of increased CVD risk with greater intakes," Dr. Burley said.

"Overall, it's encouraging data that suggest people who incorporate coffee and green tea in their diet may experience lower CVD risk in later life," she added.

Commenting on the coffee findings, Susanna C. Larsson, PhD, from the Unit of Nutritional Epidemiology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden, found it "interesting that such a small amount as 1 cup of coffee per day reduces the risk of stroke by 20% (quite a large reduction in risk)."

"Otherwise, this Japanese study confirms results from studies conducted in the US and Europe showing an inverse association between coffee consumption and stroke risk. This study adds further support that moderate coffee consumption may lower the risk of stroke," said Dr. Larsson, who was not involved in the study.

The study was supported by Grants-in-Aid for Cancer Research and the Third-Term Comprehensive Ten-Year Strategy for Cancer Control from the Ministry of Health, Labor and Welfare of Japan. The authors, Dr. Burley, and Dr. Larsson have disclosed no relevant financial relationships.

Stroke. Published online March 14, 2013. Abstract