In terms of men's health issues, prostate cancer features high on the agenda. It's the second most diagnosed cancer in men globally - closely followed by lung cancer. And it's the most common cancer in men in the UK.
Author
Daniel Kelly
Senior Lecturer in Biochemistry, Sheffield Hallam University
As the prostate is a reproductive organ with its main job being to help make semen - the fluid that carries sperm in ejaculate - researchers have long questioned the effect of sexual factors on a man's prostate cancer risk. Specifically, does ejaculation protect against prostate cancer risk?
Interestingly, there is some evidence that supports this idea. A recent review looking at all the relevant medical investigations taking place over the last 33 years showed that seven out of the 11 studies reported some beneficial effect of ejaculation frequency on prostate cancer risk.
Although the mechanisms are not completely understood, these studies fit with the idea that ejaculation can reduce prostate cancer by decreasing the concentration of toxins and crystal-like structures that can accumulate in the prostate and potentially cause tumours.
Similarly, ejaculation may alter the immune response within the prostate reducing inflammation - a known risk factor for cancer development - or by increasing immune defence against tumour cells.
Alternatively, by reducing psychological tension ejaculation may lower the activity of the nervous system which then prevents certain prostate cells from dividing too rapidly and increasing the chance of them becoming cancerous.
Despite these suggested mechanisms, in the research implying ejaculation is protective, it appears that specifics are important.
Age plays its part. Sometimes frequency of ejaculation was only protective at ages 20-29, or 30-39, and sometimes only in later life (50s and older) and actually increased the risk in younger life (20s).
Other times, ejaculation in adolescence (when the prostate is still developing and maturing) had the greatest impact on the risk of prostate cancer decades later.
But how frequent is frequent? Well, very frequent in some cases.
A study from Harvard University found that men who ejaculated 21 or more times a month enjoyed a 31% lower risk of prostate cancer compared with men who reported four to seven ejaculations per month across their lifetimes.
Similar findings have come from Australia where prostate cancer is 36% less likely to be diagnosed before the age of 70 in men who averaged about five to seven ejaculations a week compared with men who ejaculated less than two to three times a week.
Other research has a much more modest view with greater than four per month being the ejaculation frequency to give protective effects in some age groups and patients.
No firm conclusion
Drawing overall conclusions from this research is difficult, especially when the studies differ so much in the way they were conducted.
Factors like the varied populations of men investigated, the numbers of men included in the analyses, and differences in the way ejaculation frequency is measured (whether this includes intercourse, masturbation and unprompted release usually at night) can all cloud the picture.
In fact, measurement of ejaculation frequency relies on self-reporting and often from many years and decades ago. So this is an estimate at best and can be biased by attitudes, both personal and societal, towards sexual activity and masturbation potentially leading to both over- and under-reporting.
There may also be a bias in the detection of prostate tumours with highly sexually active men delaying or not going to the hospital for the fear that cancer treatment may stop their sexual activity. These men with high ejaculation frequency may therefore actually have prostate cancer that goes unreported in these studies.
It is also possible that ejaculation may not guard against prostate cancer and the links may be due to other factors. For example, men who ejaculate more often might have healthier lifestyles that lower their chances of being diagnosed with cancer.
Reduced ejaculation frequency is related to increased body mass index (BMI), reduced physical activity and divorce - all factors related to poorer general health that in turn may contribute to cancer development.
Testosterone may be important
Testosterone, the main male sex hormone, is also a crucial part of the picture.
It is well known to increase sex drive, so a man with low levels of testosterone may not have the same desire for sexual activity leading to ejaculation as a man with higher levels.
Contrary to early opinions that high testosterone levels in men raise prostate cancer risk, the current view suggests that not only does it not elevate this risk, it is actually low testosterone concentrations that increase risk. This is particularly true for men with existing prostate cancer who have a worse disease outcome when their testosterone is low.
So it may be testosterone reducing a man's risk of prostate cancer and additionally driving their motivation for sexual activity.
Despite this, most studies do not measure testosterone levels and, at best, only recognise it as a possible influencing factor. One study that did measure the male sex hormone found that men who ejaculated frequently had higher testosterone levels. And it was these men who also had a reduced risk of prostate cancer.
There are benefits of sexual activity and ejaculation beyond the prostate including positive effects on the heart, brain, immune system, sleep and mood. So while the link between ejaculation frequency and prostate cancer is not fully understood and there is a real need for more research, frequent ejaculation (within reason) will certainly do no harm, probably does good and should therefore form part of a man's healthy lifestyle.
Daniel Kelly does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
