type 2 diabetes
Potential mechanisms
The one thing still lacking with these associations, between consumption of regular coffee and decaffeinated coffee or tea and a lower risk of developing type 2 diabetes, is a plausible mechanism.
Caffeine unlikely to play a role
Since coffee and tea are the main sources of caffeine in the diet in most countries, it is difficult to directly separate an effect of caffeine from either coffee or tea. However, since decaffeinated coffee is reported to have a similar effect to regular coffee, it is unlikely that caffeine plays a role in the negative association for development of type 2 diabetes.
Antioxidant effect?
The most recent hypothesis looks at the effect of other coffee constituents, in particular antioxidants like chlorogenic acid and trigonelline. These could have a role to play through an effect on subclinical inflammation.
A Finnish study tested the effects of a progressively increasing coffee consumption (1st month abstinence, 2nd month 4 cups/day, 3rd month 8 cups/day) in obese volunteers in a medium term intervention trial. Coffee consumption appeared to have beneficial effects on some markers of subclinical inflammation, considered to be risk factors for type 2 diabetes10.
Because of its high content in antioxidant compounds11, coffee could contribute to the total antioxidant capacity of the diet that is necessary to reduce oxidative stress, in turn leading to unfavourable conditions for the development of type 2 diabetes12. This hypothesis has not yet been confirmed.
