The answer is … maybe. For many years now, conflicting studies have been published that alternately tout coffee for its beneficial properties, then condemn it as the scourge of healthy people everywhere. What’s a coffee lover to do?

One of the most widely-quoted studies of recent years indicated that coffee may reduce the risk of developing type 2 diabetes.[1] This study from Finland found that adults who drink the greatest amount of coffee (10 cups or more) cut their risk of developing diabetes from 55% (men) to 79% (women). A separate study, however, emphasizes that “is premature to advocate high coffee consumption as a means to lower risk for type 2 diabetes”, as not enough research has substantiated claims of health benefits yet.[2]

Some studies focus on caffeine rather than coffee as a whole. One such study shows that the consumption of caffeine (such as that found in coffee) significantly reduces insulin sensitivity.[3] In layman’s terms, when you consume caffeine, the insulin in your bloodstream cannot process glucose as efficiently – an obvious problem for diabetics. A study from Duke University seems to support this finding, and further suggests that drinking caffeinated beverages with meals may make the problem even worse.[4] If a diabetic has a meal (increasing the glucose to the blood) and at the same time consumes a cup of coffee (lowering the ability of the body to metabolize the increased glucose), the potential for dangerous blood sugar levels increases. Dr. James Lane, the leader of the study, advises that diabetics should probably avoid caffeine, and consequently, caffeinated coffee.

Decaffeinated coffee, on the other hand, may have much greater benefits for potential diabetics. A study from the University of Minnesota found that women who drank decaffeinated coffee significantly reduced their risk of developing diabetes in comparison to women who drank caffeinated coffee.[5] At this time, it is unclear what component(s) of coffee may be providing these benefits, nor is it clear whether the same benefits are experienced by people who have already developed diabetes.

The upshot is, the jury’s still out on how coffee affects diabetics and potential diabetics. Until more conclusive evidence is offered as to the efficacy of coffee in improving health for diabetics, moderation is probably the wisest course. And next time you reach for a cup of java, you might want to make it a decaf!

If you’d like to know more about the effects of coffee and caffeine on diabetes, speak with your health care practitioner.

[1] Jaakko Tuomilehto; Gang Hu; Siamak Bidel; Jaana Lindstrom; Pekka Jousilahti
Coffee Consumption and Risk of Type 2 Diabetes Mellitus Among Middle aged Finnish Men and Women
JAMA 2004 291: 1213-1219

[2] Rob M. van Dam, Wilrike J. Pasman, and Petra Verhoef
Effects of Coffee Consumption on Fasting Blood Glucose and Insulin Concentrations: Randomized controlled trials in healthy volunteers
Diabetes Care 27: 2990-2992.

[3] SoJung Lee, Robert Hudson, Katherine Kilpatrick, Terry E. Graham, and Robert Ross
Caffeine Ingestion Is Associated With Reductions in Glucose Uptake Independent of Obesity and Type 2 Diabetes Before and After Exercise Training
Diabetes Care 28: 566-572.

[4] James D. Lane, Christina E. Barkauskas, Richard S. Surwit, and Mark N. Feinglos
Caffeine Impairs Glucose Metabolism in Type 2 Diabetes
Diabetes Care 27: 2047-2048.

[5] Mark A. Pereira; Emily D. Parker; Aaron R. Folsom
Coffee Consumption and Risk of Type 2 Diabetes Mellitus: An 11-Year Prospective Study of 28 812 Postmenopausal Women
Arch Intern Med 2006 166: 1311-1316