A cross-sectional study examining long-term tea consumption has observed a reduced prevalence of type 2 diabetes (DM 2) among elderly people living in the Mediterranean islands. Analysis revealed that drinking 1 - 2 cups of tea per day was associated with the greatest benefit on blood glucose levels; drinking more provided no further benefit. An increase of one cup per day was associated with a 70% lower likelihood of having diabetes (95% CI 41%-86%), after adjusting for confounding variables.

Panagiotakos, D.B., Lionis, C., Zeimbekis, A., Gelastopoulou, K., Papairakleous,N., Das, U. N. and Polychronopoulos, E. (2009). Long-Term Tea Intake is Associated with Reduced Prevalence of (Type 2) Diabetes Mellitus among Elderly People from Mediterranean Islands: MEDIS Epidemiological Study. Yonsei Med. J. 50(1): 31-38.