Drinking more coffee or tea appears to lower the risk of developing type 2 diabetes, according to an analysis of previous studies reported in the Archives of Internal Medicine.
Rachel Huxley, DPhil, of The George Institute for International Health, University of Sydney, Australia, and colleagues identified 18 studies involving 457,922 participants and assessing the association between coffee consumption and diabetes risk published between 1966 and 2009.
Six studies involving 225,516 individuals also included information about decaffeinated coffee, whereas seven studies with 286,701 participants reported on tea consumption.
When the authors combined and analyzed the data, they found that each additional cup of coffee consumed in a day was associated with a 7% reduction in the excess risk of diabetes.
Individuals who drank three to four cups per day had an approximately 25% lower risk than those who drank between zero and two cups per day.
In addition, in the studies that assessed decaffeinated coffee consumption, those who drank more than three to four cups per day had about a 1/3 lower risk of diabetes than those who drank none. Those who drank more than three to four cups of tea had a 1/5 lower risk than those who drank no tea.
The apparent protective effect of tea and coffee consumption appears to be independent of a number of potential confounding variables raises the possibility of direct biological effects, the authors wrote. Because of the association between decaffeinated coffee and diabetes risk, the association is unlikely to be solely related to caffeine.
The identification of the active components of these beverages could open up new therapeutic options for the primary prevention of diabetes mellitus. The findings also pose the question of whether patients most at risk for diabetes mellitus may in the future be advised to increase their consumption of tea and coffee in addition to increasing their levels of physical activity.