@carorees, as one of our resident science geeks, could you parse these studies and report back? I did look at one, and it appeared that they used a dose of 870mg of caffeine for the study, which is MUCH more than I ever take in. I had done some research on this, as I was hoping that my black coffee on an empty stomach was not causing an insulin response. However, having done this for some months now, I think it's pretty clear that at least for me, black coffee does NOT lead to insulin response or otherwise mess with my blood sugar (doesn't make me hungry or shaky, just awake). I did not see that the study controlled for the addition (or not) of whiteners or sweeteners; seems that (especially the latter) would be significant. Some of my earlier research also indicated that having coffee by itself or with food made a difference in its effects.
There have been a number of observational studies that show coffee intake as related to a lower risk of diabetes and dementia. Of course, nothing in nutrition is that simple; you might have one good result and two bad, or vice versa. Plus, genetics is in its infancy; perhaps one day we'll be able to get a blueprint telling us our ideal diet, but until that day, we all have to make decisions about what works for us. My friend, who used to down 5-shot mochas, now drinks only tea; he finds that coffee makes him "edgy" (translate: ripping heads off). I believe it's because he needs a little theanine (a calming amino acid found in tea) with his caffeine. I have one cup of coffee per day, sometimes two, then switch to tea (all colors, including herbal). Although I appreciate the wake-up power of coffee, I drink it because I love it; I make my own using an Aeropress (look it up, it's great!). Living in the land of Starbucks, I seldom buy a premade coffee; don't like Starbucks drip, so have an Americano the once in a great while I do have coffee there. I have no use for energy drinks, and in any case, don't do high fructose corn syrup (another one of those personal health decisions). I bet most people here are familiar with that horrible shaky feeling you get when you try to compensate for sleep deprivation by overindulging in stimulants.
but coffee instead of cake (or other carb laden food) is good 
but don't add sugar to your coffee! Or...stick to having decaf with your cakes 
