Does Sex Increase or Decrease Prostate Cancer Risk?

MichaelCastleman

Posted: Aug 27, 07 7:50pm

Might sex raise men's risk for prostate cancer? That disturbing possibility has been raised by several studies over the past 10 years:

• Italian researchers found that compared with men who never married, those who were married--and presumably had more sex--had significantly greater risk of prostate cancer. For men married more than twice, risk was three times that of never-married men.
• In two studies, University of Illinois and University of Iowa researchers correlated prostate cancer risk with men's lifetime number of women sex partners. The more sex partners, the greater their risk.

Fortunately, the latest, largest study shows just the opposite--that frequent sex protects against prostate cancer. This study, by researchers at Harvard, Johns Hopkins, and the National Cancer Institute surveyed 29,000 men, aged 46 to 81. They were asked to estimate their number of weekly ejaculations during their twenties, their forties, and during the past year. Compared with men who reported seven or fewer ejaculations per month (especially during their twenties), the men who experienced 21 or more were 33 percent less likely to develop prostate cancer.

What's going on? Does sex raise prostate cancer risk? Or protect against it?

The smart money says sex is protective. In medical research, the larger the study, the more valid it is likely to be. The studies showing that sex increases risk involved a few hundred men. The study showing that sex reduces it involved 29,000.

But if sex reduces risk of prostate cancer, it's only protective if men avoid sexually transmitted infections (STIs). In women, infection with genital warts substantially boosts risk of cervical cancer. In fact, many experts now consider cervical cancer an STI. Researchers wondered if STIs might also increase risk of prostate cancer.

Many studies--including the University of Iowa study mentioned above--show that a history of STIs, especially gonorrhea and syphilis, approximately doubles prostate cancer risk. It's not entirely clear how STIs spur development of prostate cancer, but these infections cause inflammation, which may either trigger cancerous cell changes or accelerates the growth of slow-growing cancers.

Many studies have linked sexual frequency and number of partners to increased risk of STIs. So it now seems likely that it's the STIs, not the sex per se, that increases prostate cancer risk in the studies showing that finding. It seems probable that, like cervical cancer, prostate cancer is, to some extent, sexually transmitted.

Other ways to reduce prostate cancer risk include:

• Eat less meat and whole-milk dairy items. The animal (saturated) fat in meat and dairy has been strongly linked to increased risk of prostate cancer.
• Eat more fruits and vegetables. The antioxidant nutrients found in plant foods help reduce risk of all cancers, including prostate.
• Eat more tomato foods. Among fruits and vegetables, tomatoes are the most strongly protective against prostate cancer. Tomatoes contain a form of vitamin A, lycopene, which has been shown to reduce risk. Any tomato products help, but the best involve cooked tomatoes: tomato soup, sauce, pizza, etc. Cooking makes lycopene more available to the body.
• Eat more fish. Fish tend to displace meat in the diet, and less meat means less risk of prostate cancer. In addition, cold water fish, especially salmon, contain omega-3 fatty acids that may help reduce prostate cancer risk.
• Take a multivitamin with selenium. Selenium is a potent antioxidant nutrient found in plant foods. But the amount in food depends on the the soil in which it was grown. Some soils are low in selenium. It's prudent to take a supplement. Look for multivitamins that contain 50 to 100 micrograms (mcg).
• Finally, to prevent STIs, if you or your partner is nonmonogamous, use condoms every time.