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Will Coffee Raise My Blood Sugar?

Apr 25, 2011 | By Beth Greenwood
Will Coffee Raise My Blood Sugar?
Photo Credit Hot cup of coffee with smoke COFFEE image by Ivan Majtan from Fotolia.com

The level of sugar in the blood, known as the blood glucose, can be affected by a number of things. According to the American Heart Association, blood sugar that is too low can result in the condition called hypoglycemia, with symptoms of light-headedness, sweating and headache. Hyperglycemia, or a blood sugar that is too high can result in organ damage or the condition known as diabetic coma, which can be deadly. Coffee is one substance that seems to affect the blood sugar.

Coffee, Insulin and Blood Sugar

Caffeine is the active ingredient in coffee beans, tea leaves, chocolate and kola nuts. It is well-known as a stimulant and many people drink coffee for that purpose---to wake up in the morning, to gain a brief boost of energy during the day or to counteract the effects of a short night. Blood sugar and insulin are inextricably linked in the human body; when the blood sugar is too high, insulin is secreted to bring the sugar levels down. Caffeine affects the blood sugar in two ways. First it lowers insulin sensitivity, which means that the body is less likely to respond to insulin that is secreted to manage the blood sugar. Second, caffeine can actually increase blood sugar concentrations. Dr. Maria Collazo-Clavell, a specialist in internal medicine and endocrinology, points out in the Mayo Clinic Expert Answers that it is the impact of caffeine on insulin that results in blood sugar increases. According to Dr. Collazo-Clavell, 2 to 2 1/2 cups a day, the equivalent of about 250 mg of caffeine, can cause this effect.

Coffee and Blood Sugar

Dr. Rob van Dam, writing in the American Diabetes Organization's journal "Diabetes Care," in August 2004, reported on two studies which looked at coffee consumption. In the first study, healthy volunteers used one liter of coffee per day for four weeks and then for four weeks abstained from coffee and caffeine entirely. Researchers found that higher coffee intakes led to higher fasting blood sugars and higher insulin in the blood when compared to the no-coffee period. In the second study, volunteers rotated between caffeine capsules, regular paper-filtered coffee and placebo, given in random order over two week periods. In this study, the fasting blood sugar was essentially unaffected whether coffee, caffeine or placebo were ingested; however, fasting insulin levels were high with caffeine and coffee. The bottom line for both studies: higher caffeine intakes did result in higher insulin levels, and insulin affects blood sugar.

More Research

In a study reported in the May 2008 "American Journal of Clinical Nutrition", lead researcher L.L. Moisey of the Department of Human Health and Nutritional Sciences at the University of Guelph in Ontario, Canada, described another caffeine/blood sugar study. Volunteers -- all healthy males -- completed a randomized trial in which they ingested caffeinated coffee or decaffeinated coffee, followed by two different meals: one with foods that had a high glycemic index and one with foods that had a low glycemic index. The glycemic index is an indication of whether a food is likely to cause a blood sugar spike -- low glycemic index -- or less likely to do so, which is the case for high glycemic foods. Moisey stated the results showed caffeinated coffee significantly impaired blood glucose and insulin sensitivity when compared to decaf.

Considerations and Warnings

As Dr. Collazo-Clavell notes, if you are a diabetic struggling to control your blood sugar levels, it's worth limiting your caffeine intake. Diabetes is a chronic disease that should not be self-managed without input from a health care professional.

References

Article reviewed by Jenna Marie Last updated on: Apr 25, 2011

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