Men who drink the most coffee have a 60 percent lower risk of aggressive prostate cancer than those who do not drink any, according to a new study from the Harvard Medical School.

Researchers said in a news release that it was too early to say drinking coffee is a healthy habit, because it was not clear what caused the relationship between java and cancer.

"Coffee has effects on insulin and glucose metabolism, as well as sex hormone levels, all of which play a role in prostate cancer," said Kathryn M. Wilson, of Harvard.

She said her study was the first to look at coffee and different types of cancer.

Caffeine was not a key factor, Wilson said.

The study was based on results from nearly 50,000 men who were surveyed every four years. During the study, about 5,000 developed prostate cancer.