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(10):1255-65.
This is a prospective study initiated in 1994 in Japan involving 40,530 adults, aged 40-79 years. The subjects did not have stroke, coronary heart disease, or cancer at baseline. They were followed for 11 years for deaths due to all causes and for seven years for cause-specific mortality. Researchers observed an inverse relationship between green tea consumption and deaths due to cardiovascular disease and other causes in both men and women. However, no such association was found for decrease in the number of deaths due to cancer.
Although the sample size of the study is large, the number of cardiovascular disease and cancer cases was small therefore, the statistical power may not be sufficient. Other limitations of the study include patients lost to follow-up and obtaining data from self-administered questionnaires that may not be accurate. Therefore, well-designed clinical trials are needed to confirm the protective effects of green tea.
Li Q, et al. Green tea consumption and lung cancer risk: the Ohsaki study. Br J Cancer. 2008 Oct 7; 99(7):1179-84.
The Ohsaki study was a population-based cohort study of 41,440 individuals (40-79 years of age). Upon completion of a questionnaire, green tea consumption and lung cancer risk was assessed in these participants over a 7 year follow-up period. Incidence of lung cancer was no different in those who consumed green tea (¡Ý1 cup/day) and those who almost never or occasionally did (<1 cup/day). Because this study only assessed an individual's frequency of green tea consumption at the beginning of the study, individuals who altered their green tea consumption would have been misclassified.
Stockfleth E, et al. Topical Polyphenon E in the treatment of external genital and perianal warts: a randomized controlled trial. Br J Dermatol. Jun 2008;158(6):1329-1338.
The use of Polyphenon E, a defined green tea extract, for the treatment of external genital and perianal warts was analyzed in the randomized, double-blind, vehicle-controlled phase III study of 503 individuals. Polyphenon E (15 or 10%) or placebo was applied topically (3 times daily) for up to 4 months after which a 12-week follow-up period assessed recurrence in those who achieved complete clearance. Adverse events were also assessed during the treatment period. Treatment with either 15% or 10% Polyphenon E resulted in complete clearance in 53% and 51% of the participants, respectively as compared to 37% in the placebo group, and 5.9% and 4.1% recurrence rates were seen in patients using 15 or 10% Polyphenon E, respectively. Most adverse events were contained within the local application site and described as mild or moderate. Although this study showed that Polyphenon E was useful and safe for the treatment of external genital and perianal warts, its safety and efficacy for intra-anal or vaginal warts must be assessed in further studies.