Men who are very sexually active in their 20s and 30s run a higher risk of prostate cancer, suggests a new study.
The study of more than 800 men, led by the University of Nottingham, also found that frequent sexual activity in a man's forties appears to have little effect and if done in fifties it could in fact offer protection from the disease.
However, the study by UK researchers led by Dr Polyxeni Dimitropoulou attributed most of the differences to masturbation rather than sexual intercourse.
The researchers looked at the sexual practices of more than 431 men who had been diagnosed with prostate cancer before the age of 60, together with 409 controls.
All the men were quizzed on all aspects of their sex life from their twenties onwards, including how old they were when they became sexually active, how often they masturbated and had intercourse, how many sexual partners they had had and whether they had had any sexually transmitted diseases.
"We were keen to look at the links between sexual activity and younger men as a lot of prostate cancer studies focus on older men as the disease is more prevalent in men over 50," said Dimitropoulou.
He added: "Hormones appear to play a key role in prostate cancer and it is very common to treat men with therapy to reduce the hormones thought to stimulate the cancer cells. A man's sex drive is also regulated by his hormone levels, so this study examined the theory that having a high sex drive affects the risk of prostate cancer.
"What makes our study stand out from previous research is that we focused on a younger age group than normal and included both intercourse and masturbation at various stages in the participants' lives.
"Overall we found a significant association between prostate cancer and sexual activity in a man's twenties and between masturbation and prostate cancer in the twenties and thirties. However there was no significant association between sexual activity and prostate cancer in a man's forties.
"A possible explanation for the protective effect that men in their fifties appear to receive from overall sexual activity, and particularly masturbation, is that the release of accumulated toxins during sexual activity reduces the risk of developing cancer in the prostate area. This theory has, however, not been firmly established and further research is necessary."