Effect of coffee on endothelial function in healthy subjects: the role of caffeine

As I flippantly said to the friend who sent this to me. This doesn't apply to me since I'm not healthy, I've had a stroke. Way too much information for me, have your doctor analyze this and come back with specific recommendations.

Does caffeine impair endothelial function in our arteries?

Last year, a study entitled “Impact of Acute Caffeine Ingestion on Endothelial Function in Subjects With and Without Coronary Artery Disease” was published in the American Journal of Cardiology. They performed the most rigorous investigation to date, a randomized, double-blind, placebo-controlled cross-over study that found that caffeine significantly improved endothelial function. They concluded “In conclusion, acute caffeine ingestion significantly improved endothelial function assessed by brachial artery FMD in subjects with and without CAD and was associated with lower plasma markers of inflammation.” That was for the amount of caffeine found in about 2 cups of coffee, 4 cups of black tea, or 8 cups of green. Similar benefits were found previously at a higher dose (3, 6, and 12 cups respectively).
So why do studies on brewed coffee, espresso, and energy drinks show negative effects? These 3 studies show negative effects. Well, there are a lot of other substances in these beverages besides caffeine, some of which may also be removed in the decaffeination process. Since there appear to be compounds in coffee that both impair and improve endothelial function (whereas in tea, both green and black, it appears to be all improvement), one might turn to epidemiological studies to look at overall risk and benefit of coffee consumption (see, for example, my Update on Coffee and Coffee and Cancer).