Drinking caffeinated green tea and coffee could protect women and overweight men from type 2 (non-insulin dependent) diabetes. Researchers from the Osaka University, Japan analysed 17,413 men and women aged 40 to 65 years, who were free of diabetes at baseline. New cases of diabetes occurred in 231 men and 213 women over a 5-year follow up period. Those who reported drinking six or more cups of green tea per day were 33 percent less likely to develop type 2 as compared to subjects who did not consume tea. Those who reported drinking three or more cups of coffee per day were 42 percent less likely to develop the condition than non-coffee drinkers. Drinking black Chinese tea did not appear to protect against type 2 diabetes. The apparent protection was most pronounced in women and overweight men - persons at higher risk for insulin resistance, a precursor to diabetes. These findings from a Japanese population resemble results obtained in European and US populations in which people who drank seven or more cups of coffee per day had a 29 to 52 percent reduced risk of diabetes as compared to those who drank fewer cups of coffee per day or none at all. These associations are mostly due to caffeine, because green tea and coffee are both major sources of caffeine in Japan. However, further clinical studies are needed to confirm the protective effect of green tea and coffee for type 2 diabetes.
Annals of Internal Medicine,
April 2006