Between 1986 and 2006, nearly 50,000 US men working as health professionals were asked to report their average daily coffee intake every four years.
Over the 20 year period, 5,035 of the study participants were diagnosed with prostate cancer, 642 of which were fatal cases.
The results of the study which have been published in the Journal of the National Cancer Institute, revealed that those who drank six or more cups of coffee a day stood a 20 per cent reduced risk of developing cancer. Other findings included men who drank the most coffee stood a 60 per cent reduced risk of developing fatal cancer and those who drank one to three cups per day experienced a 30 per cent reduced risk of developing cancer.
The researchers found no difference between caffeinated and decaffeinated coffees, suggesting that it is not caffeine which contains the cancer fighting agent but compounds in the actual coffee.
Charities have said that the study evidence is still unclear and they do not recommend that men take up coffee drinking or drink extra in the hope of preventing prostate cancer.