Reproductive health benefits.

According to at least one study, sex appears to decrease a man’s risk of prostate cancer, and the prevention of endometriosis in women. It also promotes fertility in women by regulating menstrual patterns.

In a nutshell, the health benefits of sex in a good, solid relationship are practically endless. Yet, in planning our New Year’s resolutions, how many of us are declaring, “I think I’ll have more sex with my lover” in fulfilling any 2008 health and self-improvement goals?

While exercise on a regular basis is important to your health, sex can do so much more for you and your relationship. So before signing any dotted line for a new gym membership, consider how time allotted to an athletic club could be far more effective in your boudoir.

You can get a lot more bang for your buck in the bedroom, double your “membership” benefits, and, with sex breeding the desire for more sex, thanks to a boost in testosterone, it’s a workout plan you’re likelier to stick to.

Immunity booster

Sex can also boost general health by stimulating the immune system. A study carried out in Pennsylvania, for example, showed that sexually active university students produced more of the bacteria-fighting antigen IgA than those who didn't have any sex.

Scientists have speculated that this could be because sexually active people are potentially exposed to more infections, so their immune systems are primed to deal with them.

Quality, not quantity, seems to be important, however: people who had very frequent sex had lower IgA levels than those who had no sex at all.

This, according to Dr Carl Charnetski, who carried out the study, could be because people who were having very frequent sex might have been in relationships that were causing stress, which can make IgA levels drop.

The association between health and the nature of sex is perhaps backed up by a Japanese study in which 19 out of 42 people who had had a stroke during sex were being unfaithful at the time.