Coffee has negligible nutritional value. Coffee contains caffeine. Consuming more than 200 mg of caffeine doubles the risk of miscarriage in pregnant women. Caffeine blocks adenosine receptors, but the body adapts by creating more receptors unless a fatal dose is consumed. Caffeine lowers glucose levels impairing judgment. Caffeine stimulates insulin production and raises cortisol levels.
Coffee also contains kahweo palmitate and cafestol palmitate. These compounds raise glutathione levels in the liver, esp. the former. The latter is responsible raising cholesterol levels.
Thus in healthy people, coffee should probably only be consumed immediately before strenuous exercise, unless one is desperately trying to stay awake. Raising glutathione levels in the liver is helpful to those with chronic liver disease or those at risk.
Most everything published about coffee is biased opinion and not factual. Civilized people drink tea not coffee. In places where people live longer, they do not drink coffee.