Is a cup of Joe that bad? A cup is fine but four cups a day is linked to a higher mortality rate as compared to non-coffee drinkers, a study found.

The Aerobics Center Longitudinal Study found that drinking four cups of coffee per day is liked to a higher mortality rate - 21 percent to be exact. The mortality rate goes higher for those under 55, reports show.

The study done in a span of 16 years with subjects ages 20 to 87 shows that those who drank more of the brew died earlier than moderate drinkers or those who did not drink coffee at all. The study reveals that an increased death risk of 56 percent affects those under the age of 55.

While the study makes coffee look bad, it does not reverse previous studies done about the brew and how good it is for the body. In a study published by the National Institutes of Health last year, it shows that older adults who regularly had a cup of Joe had a "lower risk of death" thanks to its antioxidant contents.

"We're not saying that coffee is the cause of death; we just noticed coffee is associated with increased risk of death," says Dr. Carl Lavie of the Department of Cardiovascular Diseases in New Orleans' Ochsner Medical Center.

"There is some evidence that small amounts may have some beneficial effects, but we didn't find that in this cohort," Lavie adds.

"I do think it would be reasonable to use some caution at doses of four cups a day and above, and realize that a cup is probably a 6- to 8-oz. cup and not the grandes and supergrandes that are now available," the doctor said. "It appears to be safe in small to moderate amounts, and there may even be some benefits."