Around 1 in 7 men will be diagnosed with prostate cancer in their lifetime. But a new study – which is likely to be welcomed by many men – claims that having more than 20 female sexual partners in a lifetime may significantly reduce the risk of developing the disease. Sleeping with more than 20 men in a lifetime, however, is associated with increased risk of prostate cancer. Share on Pinterest Men who had slept with more than 20 women throughout their lives were 28% less likely to develop prostate cancer, according to researchers. The research team, from the University of Montreal’s School of Public Health in Canada, publish their findings in the journal Cancer Epidemiology. According to the researchers, the link between sexual activity and prostate cancer risk remains controversial. Some studies have associated high sexual activity with a greater risk of the disease, while others have suggested the opposite. In this study, the team set out to determine whether the number of sexual partners men have throughout their lifetime influences their risk of prostate cancer. They analyzed 3,208 men who were part of the Prostate Cancer & Environment Study (PROtEuS) in Montreal, Canada. Of these, 1,590 were diagnosed with prostate cancer between 2005 and 2009, while the remaining 1,618 men were free of the disease. As part of this study, all men were required to complete a questionnaire that asked about their sexual activity, as well as sociodemographic, environmental and lifestyle factors.

28% lower prostate cancer risk among men who slept with more than 20 women The team was not surprised to find that men who had a relative with prostate cancer were twice as likely to have the disease themselves. A family history of prostate cancer is a well-established risk factor. However, the researchers found that a man’s prostate cancer risk also appeared to be influenced by the number of sexual partners he had in his lifetime. Men who reported never having a sexual partner were twice as likely to develop prostate cancer than those who reported having sexual partners. However, the team found that men who had slept with more than 20 women in their lives had a 28% lower risk of developing all types of prostate cancer and a 19% lower risk of developing aggressive prostate cancer, compared with those who had slept with fewer than 20 women. Hypothesizing the reasons behind this finding, study co-author Marie-Élise Parent says: “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.” The researchers explain that some studies have suggested that the more a man ejaculates, the lower the concentrations of cancer-causing substances in his prostatic fluid. Other studies have indicated that a higher frequency of ejaculations may also reduce the production of intraluminal crystalloids in the prostate, which have been linked to higher risk of cancer. The number of sexually transmitted infections (STI) participants contracted in their lifetime did not appear to influence the risk of prostate cancer, the researchers say, noting that only 12% of men reported having at least one STI in their lives. In addition, the team found no association between the age at which the men first had sexual intercourse and prostate cancer risk.