As far as how it affects blood glucose—the jury still appears to be out.
One could do their own experiment to see what happens by checking blood glucose before caffeine and then one hour after. But it becomes challenging because so many other factors could impact your results. For starters–what is the source of caffeine? Caffeine from coffee may cause a different reaction compared to caffeine from Mountain Dew. Then of course, how much caffeine is in your “cup” of coffee and how much is in your “glass” of Mountain Dew? Are there carbohydrates in the beverage that could also impact blood sugar?
The bottom line: Caffeine probably does not have a great effect on blood glucose. But consult your doctor regarding caffeine use, especially if you have had a stroke or have high blood pressure. Most people can tolerate 200 mg to 400 mg caffeine daily (the amount in 1-2 8-ounce cups of coffee). If you are pregnant, then no more than 200 mg is generally recommended. Caffeine can cause sleeplessness. And it could increase anxiety or the “jitters.”
For more information refer to one of my favorite newsletters, Nutrition Action Healthletter. It is a great newsletter I have subscribed to for many years. There are no advertisements and the newsletter is published by a not-for-profit organization, the Center for Science in the Public Interest. The December 2012 issue had a very interesting article about caffeine, at this link.
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