In a study of over 40,000 Japanese adults enrolled in the Ohsaki National Health Insurance Cohort Study initiated in 1994, it was found that those who drank five or more cups of green tea a day had a death rate that was 26% lower than non tea drinkers at seven years into the study, and 16% at eleven years. Green tea was particularly effective in reducing the risk of heart disease, but did not apparently reduce the risk of cancer. (Green tea consumption and mortality due to cardiovascular disease, cancer and all causes in Japan. JAMA. 2006; 296:1255-1265).

A study of 1003 Japanese men indicates that higher consumption of green tea is associated with a lower prevalence of cognitive impairment. Less benefit was found for black and oolong tea, and no benefit from coffee. (Green tea consumption and cognitive function: a cross-sectional study from the Tsurugaya Project. Am J Clin Nutr 2006; 83: 355-61).

In a Chinese study, women who drank tea daily were found to have a significantly reduced risk of developing biliary stones or gallbladder cancer. Among men, who were more likely to be cigarette smokers, there was a slight non-significant reduction of risk. (Tea drinking and the risk of biliary tract cancers and biliary stones: a population-based case-control study in Shanghai, China. Int J Cancer 2006; 118: 3089-94).