Coffee is the number one source of antioxidants in the American diet, according to a 2005 University of Scranton study, exceeding wine, chocolate, tea, fruits and vegetables. Antioxidants may help prevent diseases such as heart disease and cancer.

Research from 2006 involving more than 27,000 women indicates that one to three cups of coffee daily can lower the risk of cardiovascular disease. And a 2005 study of more than 90,000 people in Japan found that daily coffee drinkers had half the rate of liver cancer when compared with less frequent consumers.

Surprisingly, coffee contains a high level of soluble dietary fiber—more than other beverages like wine or orange juice. That may explain why a 2002 study of nearly 81,000 women found that those who drank four or more cups a day had about a 25 percent lower risk of gallstones than nondrinkers.

Something in coffee seems to help insulin do its job: Women who drank three to four cups a day had a 29 percent lower risk of diabetes, according to a study from Finland.

There's a grab bag of other preventive benefits, too: protection against chronic liver disease—such as alcohol-related cirrhosis—in people who are at high risk, for example. And food chemists have discovered a substance in coffee that may help ward off colon cancer.

You might even want to make a cup of joe your preworkout beverage: A small study published in March found that a dose of caffeine roughly equal to that in two cups of coffee reduced postexercise muscle soreness by nearly half. Caffeine blocks adenosine, the theory goes, which is a chemical linked to inflammation.