Well, I do know from MUCH testing and observation that coffee caffeine makes my blood sugar go UP UP UP!! (I'm diabetic and I test *everything* I eat--many times if necessary to determine exactly what kind of affect on my BG it has) I do occasionally drink sodas with caffeine and I drink tea, but I haven't found that they have any affect at all. Which I find interesting. Decaf coffee has virtually no affect at all.