The Advisory Report to the USDA and HHS on the 2015 Dietary Guidelines gave a thumbs up to moderate coffee consumption, noting that it is associated with a reduced risk for type 2 diabetes:
Strong evidence shows that consumption of coffee within the moderate range (3 to 5 cups per day or up to 400 mg/d caffeine) is not associated with increased long-term health risks among healthy individuals. In fact, consistent evidence indicates that coffee consumption is associated with reduced risk of type 2 diabetes and cardiovascular disease in adults. Moreover, moderate evidence shows a protective association between caffeine intake and risk of Parkinson’s disease.
The authors warn care should be taken to minimize calories from added sugar and dairy or non-dairy fats.