Kuriyama S, Shimazu T, Ohmori K, et al: Green tea consumption and mortality due to cardiovascular disease, cancer, and all causes in Japan—the Ohsaki Study. JAMA. 2006;296:1255-1265.
Background.
Experimental data suggest that the polyphenols found in green tea may have a chemopreventive effect against cancer and cardiovascular disease. However, there are few data on the health benefits of green tea for humans. A Japanese insurance database was used to study the relationship between green tea consumption and all-cause and disease-specific mortality. Methods. The population-based study included data on 40,530 Japanese adults aged 40 to 79 years. At baseline in 1994, all subjects were free of stroke, coronary heart disease, and cancer. All-cause mortality was assessed over 11 years’ follow-up and mortality from cardiovascular disease and cancer over 7 years’ follow-up. At both times, the follow-up rate was over 86%.
Results.
Especially for women, greater consumption of green tea was associated with lower all-cause mortality and mortality from cardiovascular disease. On multivariate analysis, hazard ratios for all-cause mortality were 0.93 for men who drank 1 to 2 cups of green tea per day, 0.95 for 3 to 4 cups per day, and 0.88 for more than 5 cups per day (compared to less than 1 cup per day). For women, the hazard ratios were 0.98, 0.82, and 0.77, respectively. Green tea consumption had an even stronger inverse association with cardiovascular disease: for women, hazard ratios were 0.84 at 1 to 2 cups per day, 0.69 at 3 to 4 cups per day, and 0.69 at 5 or more cups per day. The cardiovascular protective effect of green tea appeared strongest for stroke mortality. There was no significant association between green tea consumption and cancer mortality.
Conclusion.
This large Japanese cohort study suggests that allcause and cardiovascular disease mortality are lower among subjects with higher consumption of green tea. Drinking green tea has no apparent protective effect against cancer mortality.
Commentary:
In this study, adults in Japan who consumed 5 or more cups of green tea a day had a 16% lower risk of all-cause mortality during the 11 years of follow-up, including cardiovascular disease. This inverse relationship between mortality and green tea consumption was stronger in women. Interestingly the relationship between black tea and mortality was much weaker. After water, tea is the world’s most commonly consumed beverage. The polyphenols in green tea have been the subject of much interest, particularly in the area of cardiovascular disease.
Copyright 2007, EXPLORE: The Journal of Science and Healing
Reprinted with permission.
For additional information on Green Tea and Cancer, visit http://aje.oxfordjournals.org/cgi/content/abstract/167/1/71?etoc