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.