In a supplement to the December 2013 issue of the American Journal of Clinical Nutrition that covered the Fifth International Scientific Symposium on Tea and Human Health, researchers from the University of California, Los Angeles report their conclusion of a protective effect for tea drinking against stroke.
“Considerable observational human evidence suggests a preventive association of tea or flavonoid intake on specific subcategories of cardiovascular disease,” the authors write. “When the outcome is restricted to stroke incidence or mortality, the association seems to be the strongest and most consistent.”
Lenore Arab and her colleagues reviewed five meta-analyses of human studies of tea or flavonoid consumption and cardiovascular disease or stroke published between 2001 and 2011. (The disease-preventive properties of tea have been attributed to its flavonoid content.) The meta-analyses included 15 case-control studies, 43 cohort studies, and 1 cross-sectional study involving green and/or black tea intake. A 21% lower risk of both stroke incidence and mortality from stroke was observed among those with high tea intake in comparison with low, and for those with a high intake of flavonoids, the risk was 20% lower. A similar reduction was associated with each three cups of tea consumed. A search for new studies published subsequent to the meta-analyses included in the current research revealed additional studies that supported the protective effect of tea-drinking against stroke.
Protective mechanisms for tea suggested by the authors include a reduction in blood pressure and improved endothelial function.