Glucose tests provide a way to measure your blood sugar levels. Normally, your doctor recommends a fasting glucose test after not eating overnight, usually doing the test first thing in the morning. After meals, blood sugar levels show whether blood sugar rises abnormally high after eating. Drinking or taking caffeine may affect blood sugar results, even if you take it in a form that contains no calories, like capsules. This effect has occurred in people with and without diabetes in some, but not all, clinical studies.
Importance
Keeping track of your blood sugar levels plays an important role both in diabetes management and prevention. If you're diabetic, your doctor may base your medication doses on your blood sugar levels. If you're prediabetic, checking blood sugar levels provides information on how well measures such as diet and exercise are working on preventing you from developing diabetes.
Studies in Diabetics
Several studies have shown that caffeine intake affects blood sugar levels in people with diabetes. A Duke University study reported in the August 2004 issue of the American Diabetes Association's magazine "Diabetes Care" found that ingesting 250 mg of caffeine did not affect fasting blood sugar levels in diabetics compared to placebo. However, when diabetics ingested another 125 mg of caffeine followed by a meal, post-prandial blood sugars rose higher in the group that took the caffeine. A Canadian study published in the October 2004 issue of the "Journal of Nutrition" found similar results in men with diabetes.
Studies in Healthy Subjects
A Canadian study conducted by the University of Guelph and published in the July 2001 issue of the "Canadian Journal of Physiology and Pharmacology" tested the effects of a 5 mg/kg dose of caffeine vs. placebo on healthy males. Fasting blood glucose levels did not change in those who took the caffeine dose and then had their blood sugar levels drawn; however, both insulin levels, which control blood glucose and blood glucose levels, rose for the last 90 minutes after ingestion of 75 g of glucose in the oral glucose tolerance test. A review of data from the Nurses' Health Study II conducted by researchers from the Harvard School of Public Health and published in the February 2006 issue of "Diabetes Care" found that coffee drinkers had a lower risk of developing diabetes.
Considerations
Caffeine intake could not only raise blood glucose levels after eating but could also keep levels higher for longer.Caffeine also may increase insulin resistance, a factor in the development of type 2 diabetes. Some studies, on the other hand, have shown a reduced risk of developing diabetes in coffee drinkers. If you have or are at risk for developing type 2 diabetes, talk with your doctor about your caffeine intake to determine how much caffeine ingestion is safe for you.
References
- "Diabetes Care"; Caffeine Impairs Glucose Metabolism in Type 2 Diabetes; James Lane, Ph.D.; August 2004
- Mayo Clinic; Caffeine: Does It Affect Blood Sugar?
- "The Journal of Nutrition"; Caffeine Ingestion Before an Oral Glucose Tolerance Test Impairs Blood Glucose Management in Men with Type 2 Diabetes; Lindsay Robinson, et al.; October 2004
- "Diabetes Care"; Coffee, Caffeine, and Risk of Type 2 Diabetes ; Rob van Dam, et al.; February 2006
- "Canadian Journal of Physiology and Pharmacology"; Caffeine Ingestion Elevates Plasma Insulin Response in Humans During an Oral GlucoseTolerance Test; T. Graham, et al.; July 2001
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