fréquente protège des hommes...

A recent US study, which followed nearly 30,000 men over eight years, showed that those that ejaculated most frequently were significantly less likely to develope prostate cancer. The results confirm the results of a smaller Australian study revealed by New Scientist in July 2003. In the latest study, the group with the highest lifetime average of ejaculation - 21 times per month - were a third less likely to develop the cancer than the reference group, who ejaculated four to seven times a month.

Michael Leitzmann, at the National Cancer Institute in Maryland, and colleagues set out to test a long-held theory that suggested the opposite - that a higher ejaculation rate raises the risk of prostate cancer. "The good news is it is not related to an increased risk," he told New Scientist. In fact, it "may be associated with a lower risk."

"It goes a long way to confirm the findings from our recent case-control study," says Graham Giles, who led the Australian study. He praises the study's large size - including about 1500 cases of prostate cancer. 

Furthermore, it was the first to begin by following thousands of healthy men. This rules out some of the biases which might be introduced by asking men diagnosed with prostate cancer to recall their sexual behaviour retrospectively.

At the start of the study, the men filled in a history of their ejaculation frequency and then filled in further questionnaires every two years. Men of different ages varied in how often they ejaculated, so the team used a lifetime average for comparisons.

Compared to the reference group who ejaculated four to seven times a month, "each increase of three ejaculations per week was associated with a 15 per cent decrease in the risk of prostate cancer", says Leitzmann. "More than 12 ejaculations per month would start conferring the benefit - on average every second day or so," he says.

However, while the findings are statistically significant, Leitzmann remains cautious. "I don't believe at this point our research would warrant suggesting men should alter their sexual behaviour in order to modify their risk." 

A further caveat is that the benefit of ejaculation was less clear in relation to the most dangerous, metastasising form of prostate cancer, compared to the organ-confined or slow-growing types.

Leitzmann and Giles both agree that there are biologically plausible ways that ejaculating frequently might prevent prostate cancer. "Increased ejaculation may allow the prostate gland to clear itself of carcinogens or of materials that form a substrate for the development of carcinogens," Giles told New Scientist.

Another theory is that frequent drainage of prostate fluid stops tiny crystalloid microcalcifications - which have been associated with prostate cancer - from forming in the prostate duct, says Leitzmann.

Giles notes that neither study examines ejaculation during the teenage years - which may be a crucial factor. But he says: "Although much more research remains to be done, the take home message is that ejaculation is not harmful, and very probably protective of prostatic health - and it feels good!"

Commenting on the study, Hastings based sex philosopher Seb Cox said "Now I know what goes on at colleges. The study is great, but, misses a couple of very serious points. What they don't take into consideration is the stenght of ejaculation. The stronger the ejacualtion, the better it is for the health of your prostate. It's not good enough just to encourage men to be wankers, we have to encourage them to become EXCELLENT, to stick their fingers up their arses, to get in tune with their prostate and to have orgams that make them nearly pass out, physically. Then they, both the intellectuals and the wankers, will be ready for the slightly more advanced study, The Comradeship of Shared Masculinity."

Journal reference: Journal of the American Medical Association (vol 291, p 1578) 

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