Coffee acutely modifies GI hormone secretion and glucose tolerance: glycemic effects of chlorogenic acid and caffeine. For me, coffee falls into the “everything in moderation” category (incidently, broccoli and other veggies from the brassica family are not in the moderation category–overindulge). What I do have a problem with is coffee drinkers who cannot function until their fifth gallon of coffee–these people usually have adrenal insufficiency that they are trying to override with super-physiologic doses of caffeine. For everyone else, coffee has shown to have benefits from their polyphenols.
AJCN — Abstracts: Johnston et al. 78 (4): 728