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.
Ejaculation May Lower Prostate Cancer Risk
The findings, published in the April 7 issue of The Journal of the American Medical Association, are based on data collected from nearly 30,000 predominately white men aged 46 to 81.
At the start of the study, men provided information on ejaculation frequency in their 20s, 40s, and in the previous year (1991). Ejaculation frequency included sexual intercourse, masturbation, and nighttime ejaculations that can occur during sleep. The men were then monitored for eight years.
Researchers found most categories of ejaculation frequency were unrelated to prostate cancer risk. But when they looked at men in the highest category of ejaculation frequency, they found evidence of a protective effect.
"When you look at the data in a little bit more detail, you do see that not only is there not an increased risk, but there is potentially even the possibility of a slight decrease in risk with high ejaculation frequency," says researcher Michael Leitzmann, MD, an investigator at the National Cancer Institute in Bethesda, Md. Leitzmann conducted the research during a post-doctoral fellowship at Harvard University.
Leitzmann says researchers suspected that ejaculation frequency might be a marker of a healthier, more active lifestyle. But when they accounted for diet, exercise, and other risk factors for prostate cancer, the link between frequent ejaculation and lower prostate cancer risk remained.
Study Raises Biological Questions
Researchers say the findings raise several questions about the biological role of sexual activity and ejaculation in the development of prostate cancer.
Leitzmann says that until now, sexual activity had been associated with prostate cancer risk due to the hormone hypothesis. The male sex hormone testosterone is known to spur the growth of prostate cancer cells and it also fuels the male sex drive. Therefore, it had been proposed that very sexually active men had a higher risk of prostate cancer because they had higher testosterone levels.
But he says this theory has its shortcomings because testosterone levels alone do not predict prostate cancer risk and they do not appear to correlate with sexual desire as much as previously thought.
Instead, researchers say ejaculation may protect the prostate through a variety of biological mechanisms that merit further research, such as:
- Flushing out cancer-causing substances. Frequent ejaculation may help flush out retained chemical carcinogens in the prostate glands.
Reducing tension. The release of psychological tension that accompanies ejaculation may lower nervous activity associated with stress and slow the growth of potentially cancerous cells in the prostate.
Promoting rapid turnover of fluids. Frequent ejaculation may help prevent the development of mini-crystals that can block ducts within the prostate gland, reducing cancer risk.
The Fine Print
Although researchers found frequent ejaculation appeared to lower the risk of developing prostate cancer, it's unclear how ejaculation may affect men destined to develop or already in the early states of prostate cancer. Men who reported high ejaculation frequency throughout their lives and in the last year appeared to have a higher risk of developing advanced prostate cancer, but researchers say the numbers were too small to draw any firm conclusions.
Since the study consisted of white men predominantly, researchers also say that the study results only apply to middle-aged white men. Black men are more likely to develop prostate cancer than white or Asian men.
Martin Resnick, MD, chairman of the department of urology at Case Western Reserve University in Cleveland, says it's always been a question of whether prostate function as indicated by sexual activity might affect prostate cancer risk either positively or negatively.
"There have been some studies in the past that showed individuals that have been more promiscuous, had more sexual partners, or had an earlier onset of sexual activity had higher incidence of prostate cancer," says Resnick. "But those are old studies."
He says this study offers new information that sexual activity may not be negatively associated with prostate cancer, and it's reasonable to believe that a "use it or lose it" principle may apply to overall prostate health.
But researchers stress that until more is known about the role of ejaculation and prostate cancer, researchers say men shouldn't change their sexual behavior.
"This one study doesn't warrant any recommendations. Men shouldn't go out and start changing their habits," says Leitzmann.
According to the American Cancer Society, prostate cancer is the most common type of cancer found in American men, other than skin cancer. They estimate that about 230,900 new cases of prostate cancer will be diagnosed this year in the U.S., and close to 30,000 American men will die of this disease.
The exact cause of prostate cancer is unknown, and the only proven risk factors for the disease are increasing age, family history of the disease, and race or nationality (prostate cancer is most common in North America and Europe). A diet high in fat or red meat and lack of physical activity are also thought to increase the risk of prostate cancer. Many experts believe that regular screenings for prostate cancer by a doctor can help find prostate cancer early -- when it's curable.