Not only that, but it looks like previous thoughts that coffee consumption negatively impacts heart disease, hypertension, cancer, and bone loss are all mistaken. Unfortunately, caffeine consumption does seem to have some positive correlation with weight gain. Fortunately, the positive health benefits are likely to more than make-up for this:
Hydration. [P]eople who consumed drinks with up to 550 milligrams of caffeine produced no more urine than when drinking fluids free of caffeine. So even a Starbucks grande, with 330 milligrams of caffeine, will not send you to a bathroom any sooner than if you drank 16 ounces of pure water. Drinks containing usual doses of caffeine are hydrating and, like water, contribute to the body’s daily water needs.
Well-being. Probably the most important effects of caffeine are its ability to enhance mood and mental and physical performance. At consumption levels up to 200 milligrams (the amount in about 16 ounces of ordinary brewed coffee), consumers report an improved sense of well-being, happiness, energy, alertness and sociability, Roland Griffiths of the Johns Hopkins School of Medicine reported, although higher amounts sometimes cause anxiety and stomach upset.Much more after the link. Also, read more about coffee here. [PDF]
Parkinson's Disease. Recent disease-related findings can only add to coffee’s popularity. A review of 13 studies found that people who drank caffeinated coffee, but not decaf, had a 30 percent lower risk of Parkinson’s disease.
Diabetes. Another review found that compared with noncoffee drinkers, people who drank four to six cups of coffee a day, with or without caffeine, had a 28 percent lower risk of Type 2 diabetes. This benefit probably comes from coffee’s antioxidants and chlorogenic acid.