WASHINGTON (AFP) ― More is better when it comes to drinking coffee to ward off the risk of deadly prostate cancer, according to a major U.S. study released by researchers at the Harvard School of Public Health.

Men who drank six or more cups per day had a 60 percent lower risk of developing the most lethal type of prostate cancer and a 20 percent lower risk of forming any type of prostate cancer compared to men who did not drink coffee, it said.

Even just one to three cups per day was linked to a 30 percent lower risk of developing lethal prostate cancer.

“Few studies have specifically studied the association of coffee intake and the risk of lethal prostate cancer, the form of the disease that is the most critical to prevent,” said Harvard associate professor and senior author Lorelei Mucci.

“Our study is the largest to date to examine whether coffee could lower the risk of lethal prostate cancer,” she said.

The effects were the same whether the coffee was caffeinated or decaffeinated, leading researchers to believe the lower risk could be linked to the antioxidant and anti-inflammatory benefits of coffee.

Prostate cancer is the most commonly diagnosed form of cancer in U.S. men, but it is not always deadly.

A blood test can detect it early, and the cancer can be graded on what is known as a Gleason score; the higher the score the more likely the cancer is to spread.

There are 16 million survivors of prostate cancer worldwide, and one in six men in the United States will get prostate cancer during their lifetime.

Risk factors are typically linked to Western high-fat diets, heredity, alcohol and exposure to chemicals.

The study examined 47,911 U.S. men who reported on how much coffee they drank every four years from 1986 to 2008.

Over the course of the study, a total of 5,035 cases of prostate cancer were reported, including 642 fatal, or metastatic, cases.

The lower risk seen in coffee drinkers remained even after researchers allowed for other factors that typically boost risk and were more often seen in coffee drinkers than in abstainers, such as smoking and failure to exercise.