Your blood glucose, or blood sugar, is controlled by the hormone insulin. According to a 2005 article published in "Metabolic Syndrome and Related Disorders," caffeine makes the body less sensitive to insulin, but coffee actually decreases the risk of developing type 2 diabetes, a disease in which blood sugar is consistently too high.
Coffee and Insulin
Dr. James Lane reported in the March 2011 "Journal of Caffeine Research" that at least 17 studies have shown caffeine in coffee, tea and soft drinks can decrease the body's ability to respond to insulin. This effect means blood sugar will rise after you eat carbohydrates, in spite of insulin secretion, because the insulin is not effective. Lane says the studies were performed on healthy volunteers and the dose of caffeine was roughly equivalent to 2 to 3 cups of brewed coffee.
Caffeinated Coffee and Blood Glucose
Dr. Rob van Dam adds that caffeinated coffee definitely does affect blood glucose. Van Dam reported a study in the August 2004 journal "Diabetes Care" in which healthy volunteers who drank one liter of coffee per day for four weeks had higher fasting blood sugar levels. During the four weeks when the volunteers abstained from caffeine in any form, their blood sugars were lower. Van Dam and his colleagues reported that caffeine's effect on insulin was the most likely cause of the elevated blood sugar levels in the study participants.
Caffeine and Blood Glucose
In another study reported in the October 2004 "Journal of Nutrition," researchers found that blood glucose was elevated and stayed elevated over a longer period after caffeine intake compared to a placebo. The patients in this study were diabetics, and the authors commented that their research could have implications for the use of caffeine by the diabetic population. However, these researchers also noted that they had used pure caffeine, and coffee contains a number of biologically active compounds that may act as an antagonist to caffeine.
Coffee, Diabetes and Blood Sugar
Although caffeine can cause the blood sugar to rise, coffee consumption actually seems to improve the body's ability to keep glucose under control and to decrease the risk of diabetes.
An article in the January 2006 "Nutrition, Metabolism and Cardiovascular Disease" reports that drinking regular and decaffeinated coffee was associated with a lower risk of type 2 diabetes. The author says it is likely other compounds in the coffee play a role and may counteract the effect of caffeine on insulin.
References
- "Journal of Caffeine Research"; Caffeine, Glucose Metabolism, and Type 2 Diabetes; James D. Lane, Ph.D.; March 2011
- Mayo Clinic; Type 2 Diabetes Expert Answers: Caffeine: Does it Affect Blood Sugar?; M. Collazo-Clavell M. D.; February 2010
- "Diabetes Care"; Effects of Coffee Consumption on Fasting Blood Glucose And Insulin Concentrations Randomized Controlled Trials in Healthy Volunteers; R. M. van Dam, P.H.D., et al.; August 2004
- "Journal of Nutrition"; Caffeine Ingestion Before an Oral Glucose Tolerance Test Impairs Blood Glucose Management in Men with Type 2 Diabetes; Lindsay E. Robinson, et al.; October 2008
- "Nutrition, Metabolism and Cardiovascular Disease"; Coffee and type 2 Diabetes: From Beans to Beta-Cells; R.M. van Dam; January 2006
