October 10, 2015

The Archives of Internal Medicine, published by the American Medical Association (AMA), has recently released a comprehensive report on the benefits of coffee and tea for prevention of type 2 diabetes. The report is a review of published studies and a pooled analysis of all the data (called a “meta-analysis”).

Drinking coffee, decaf coffee, green tea or black tea was associated with a reduction in the risk of developing diabetes. For coffee, the reduction was dose-dependent, which is to say that the more coffee or tea drunk, the greater the reduction in risk, about 7% per cup up to six cups a day.

The authors state that the effects may be due to the presence of phenolic compounds in coffee or tea that increase sensitivity to the effects of insulin, the hormone responsible for keeping blood sugar levels low.

The research described in this review is all observational: it follows the dietary habits of people and observes what diseases they develop. Observational research is sometimes inconclusive. To demonstrate the reality of the effect, a controlled interventional study would need to be done in which people were given pills of coffee or tea or a placebo and then followed for several years.