There is growing evidence that more frequent ejaculation may have a role in preventing prostate cancer. The reason is still unknown – e.g. whether it is a clearing of tumour-triggering agents, some other mechanism or the possibility that regular ejaculators tend to be in better general health. Research published in 2016 provides the strongest evidence so far that men who reported more frequent ejaculation during their adult life are less likely to be diagnosed with prostate cancer. The US study, involving more than 31,000 men, found men who reported ejaculating 21 times per month when aged in their 20s and 40s were 20 per cent less likely to develop prostate cancer than those who ejaculated four to seven times per month. The association was first reported in 2003 by Australian researchers. A Cancer Council Victoria study into the relationship between prostate cancer and ejaculation in men aged under 70 found that the more frequently men ejaculated between the ages of 20 and 50, the less likely they were to develop prostate cancer in older age. Men who reported ejaculating on average seven or more times per week when in their 20s were one-third less likely to develop prostate cancer than men who ejaculated less than three times a week at that age. More evidence is required before we can conclude that frequent ejaculation actually prevents prostate cancer. For example, researchers couldn’t rule out that men who reported more frequent ejaculation were healthier or had another “vitality factor” that could explain their lower prostate cancer risk. The impact of sexual activity on health is complex due to its multifaceted nature and possible co-factors. A 2016 Cancer Council NSW study of around 2000 men associated an increased risk of prostate cancer with sexual activity, with men who reported a greater number of lifetime sexual partners or started sexually active earlier having a higher risk of prostate cancer.