A surefire way of holding off that scourge of male health, prostate cancer, is to sleep with lots of women - according to the latest research. However, perhaps unfortunately for those gentlemen inclined that way, sleeping with a lot of other men has quite the opposite effect.

These bombshells originate in a study from Canadian health researchers, who have done a survey in which 3,208 men responded to a questionnaire which included questions on their sex lives. Of these men, 1,590 were diagnosed with prostate cancer, while 1,618 men were part of the control group.

We are told:

When a man has slept with more than 20 women during his lifetime there is a 28 per cent reduction in the risk of having prostate cancer (all types), and a 19 per cent reduction for aggressive types of cancer.

In many cases prostate cancer is non-aggressive, causing varying levels of discomfort but otherwise leaving the sufferer alone. However it sometimes becomes aggressive, spreading to other parts of the body with serious consequences, and as a result - it being very common, especially among older chaps - it's the second biggest killer cancer in men after lung cancer.

The prostate is heavily involved in sex, producing some of the stuff that makes up the seminal fluid. It would seem that putting it to frequent use can have beneficial consequences.

"It is possible that having many female sexual partners results in a higher frequency of ejaculations, whose protective effect against prostate cancer has been previously observed in cohort studies," Professor Marie-Elise Parent explains.

So it's good news for those Reg readers who have managed or are managing to get a few notches onto the old bedpost - or anyway, for the heterosexuals among this group. Lots of male partners appears to actually be a bad thing from the prostate cancer viewpoint:

The data indicate that having only one male partner does not affect the risk of prostate cancer compared to those who have never had sexual intercourse with a man. On the other hand, those who have slept with more than 20 men are twice as likely to be diagnosed with prostate cancer of all types compared to those who have never slept with a man. And their risk of having a less aggressive prostate cancer increases by 500% compared to those who have had only one male partner.

Parent and her colleagues have only "highly speculative" theories to explain this.

"It could come from greater exposure to STIs, or it could be that anal intercourse produces physical trauma to the prostate," speculates the prof.

The study is published in full in the journal Cancer Epidemiology. ®