April 6, 2004 -- Frequent ejaculation, whether it happens during sexual intercourse, masturbation, or a dream, isn't likely to increase men's risk of prostate cancer. In fact, new research suggests it may have the opposite effect and help protect the prostate.

Researchers say it's too soon to recommend that men change their sexual habits in an attempt to lower their prostate cancer risk. However, the study raises interesting questions about the role of ejaculation and sexual behavior in the development of prostate cancer.

Previous studies have linked frequent sexual activity to a higher risk of prostate cancer, but this new, large study found ejaculation frequency was not associated with prostate cancer risk except in the highest category. Men who ejaculated most often actually had a 33% lower lifetime risk of prostate cancer, and this relationship grew stronger as men grew older.

For example, men who reported 21 or more ejaculations per month in their 40s had a 32% lower risk of prostate cancer later in life compared with those who reported between four and seven ejaculations per month. Men who reported more than 21 monthly ejaculations in the previous year had a 51% lower risk of prostate cancer.

Overall, an average of 21 or more ejaculations a month during a man's lifetime decreased the risk of prostate cancer later in life by 33%. And each increase of three ejaculations per week during a man's lifetime was associated with a 15% reduction in prostate cancer risk.