Aggressive prostate cancers, known as "tigers," are far more likely to prove lethal than milder forms of the disease.

Study leader Dr Kathryn Wilson, from Harvard Medical School in Boston, said, "Coffee has effects on insulin and glucose metabolism as well as sex hormone levels, all of which play a role in prostate cancer. It was plausible that there may be an association between coffee and prostate cancer.

"Very few lifestyle factors have been consistently associated with prostate cancer risk, especially with risk of aggressive disease, so it would be very exciting if this association is confirmed in other studies. Our results do suggest there is no reason to stop drinking coffee out of any concern about prostate cancer."

Components in coffee other than caffeine were thought to be responsible for the findings. Coffee contains many biologically active compounds including antioxidants and minerals, said the scientists.

The results were presented at the American Association for Cancer Research meeting "Frontiers in Cancer Prevention Research" in Houston, Texas.

Helen Rippon, head of research management at The Prostate Cancer Charity, said, "Coffee is one of the most popular drinks in the world, and so it is important that we fully understand any impact drinking it has on health. The research evidence so far on the relationship between caffeinated drinks and prostate cancer has been quite mixed, and has largely focused on the risk of developing the disease and the role that drinks like tea and coffee might have in cancer prevention.

"This large scale study looked instead at whether coffee drinking might influence the aggressiveness of prostate cancer in men who do develop the disease. This research does provide a clue that coffee drinking might reduce the likelihood of a man being diagnosed with a more advanced prostate cancer, although there is still more research to do to confirm this and to uncover which component of coffee could be responsible.

"We would not recommend that men cultivate a heavy coffee drinking habit on the back of this research, not least because a high caffeine intake can cause other health problems. However, men who already enjoy a regular cup of coffee should be reassured that they do not need to give this up for the sake of their prostate."

Each year around 35,000 men are diagnosed with prostate cancer in the U.K., and 10,000 die from the disease.  

From the December 21, 2009, Prepared Foods E-dition