Caffeine impairs glucose metabolism in type 2 diabetes.


American Diabetes Association (Summary)

Authors:  James D. Lane, PhD, Christina E. Barkauskas, AB, Richard S. Surwit, PHD and Mark N. Feinglos, MD


Acute administration of caffeine impaired postprandial glucose metabolism in these diabetic patients. In contrast to nondiabetic subjects (3–5), our subjects demonstrated exaggerations of both glucose and insulin responses when caffeine was ingested with carbohydrates. Such effects could have implications for the clinical management of type 2 diabetes.

Caffeine only affected postprandial responses. Mealtime hyperglycemia may be a more accurate predictor of HbA1c (6) and cardiovascular mortality (7,8) than fasting hyperglycemia. Strategies for controlling postprandial glucose metabolism are gaining importance in diabetes management. Caffeine abstinence may have beneficial effects that compare favorably with oral agents used to control postprandial glucose. Acute abstention reduced glucose increases following the mixed meal by 21%, which compares favorably to the 30% reductions observed in clinical trials of acarbose (9) and the short-acting insulin secretagogue nateglinide (10). If the results of this acute study extrapolate to chronic abstinence, quitting caffeine could be beneficial.

These results are limited by a small sample size. Furthermore, the study tested the effects of caffeine only and not the effects of coffee or tea. Both beverages contain numerous organic compounds, some of which might augment or offset the effects of caffeine (11). Despite these limitations, our results raise concerns about the potential hazards of caffeine for patients with type 2 diabetes and possibly for individuals who are glucose intolerant or “pre-diabetic.” Repeated exaggerations of postprandial glucose, resulting from daily consumption of caffeinated beverages with meals, could produce higher average glucose levels that increase the risk of diabetes complications.

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