"Ejaculating at least 21 times a month significantly reduces a man's risk of prostate cancer," is the headline on the Mail Online. This is based on research from the US that asked men how often they ejaculated per month and subsequent reporting of prostate cancer.
They found that men who ejaculated 21 times or more a month were less likely to report prostate cancer at follow-up than those ejaculating four to seven times per month.
However, it does not prove that ejaculating more frequently prevents cancer, only that it is associated with a reduction in risk. It might be that a range of other factors such as genetics, lifestyle, number of children, diet, nature of sexual activity and education contribute to this risk, but we cannot say for sure what factors might increase the risk.
The researchers offer a number of hypotheses why ejaculation may help reduce prostate cancer risk, such as reducing stress or keeping cell metabolism well regulated. But these suggestions remain in the realm of speculation.
Despite any lurid tales you may have heard growing up, masturbation is entirely safe. So if you want to do it as a preventative method then it wouldn't pose any health risks.
Initial signs of prostate cancer usually involve problems with urination, such as needing to urinate more frequently, due to the prostate getting larger. While prostate enlargement can occur as men grow older, it is important to check symptoms like these with your GP.
Where did the story come from?
The study was carried out by researchers from Boston University School of Public Health, Harvard T.H. Chan School of Public Health, and Harvard Medical School, all in the US. It was funded by the National Cancer Institute and grants from the Prostate Cancer Foundation Young Investigator Award.
The UK media reporting was generally accurate and, as you would imagine, some of the coverage, and the associated photos, were a little tongue in cheek.
The Sun's claim that "having 21 orgasms a month could be the key to preventing CANCER in men because it helps the prostate 'flush out toxins'" is unsupported. The claim that it flushes out toxins was not studied in this research and it is not proven that ejaculation is a "key to preventing cancer".
What kind of research was this?
This was a cohort study following up male health professionals from 1992 for 18 years. It was designed to look at multiple health outcomes. In this particular analysis, the researchers aimed to determine their ejaculation frequency at different ages and whether it was associated with likelihood of getting prostate cancer.
A cohort study is best for this type of research as it allows reporting of people's habits and lifestyles without interfering and means a lot of people can be followed over a long period of time to see long-term health outcomes. However, a cohort study cannot control for other factors that may affect outcomes, a randomised controlled trial would be needed for that – but they are very time consuming, expensive, and intrusive on people's lives.
What did the research involve?
Researchers took data from the Health Professionals Follow-up Study, a study that began in 1986 aiming to look at links between men's lifestyles and health outcomes. They took 31,925 men's answers to a questionnaire about ejaculation frequency and looked to see if there was an association with developing prostate cancer.
The men were aged between 40 and 75 at baseline in 1986 and were all health professionals. They were asked questions about medical history and lifestyle every two years. Ejaculation frequency was assessed in the 1992 questionnaire.
The specific question asked was: "On average, how many ejaculations did you have per month during these ages?: age 20-29; age 40-49; past year."
The frequency of ejaculation per month was recorded in the following categories:
- over 20
Follow-up was complete for 96% of the men still alive.
For men reporting they had prostate cancer, medical records were obtained to determine age at diagnosis; prostate specific antigen (PSA) level – PSA is a hormone associated with prostate enlargement; and tumour stage and grade.
To see if the link between ejaculation frequency and prostate cancer differed according to the specific characteristics of the cancer, clinical information was used to group prostate cancer into four risk categories:
- Low risk = T1/T2 tumour, PSA<10 nanograms (ng) per millilitre (ml), Gleason score 6 (the Gleason score is a measurement of how likely the cancer is to spread out of the prostate into surrounding tissue)
- Intermediate risk = T1/T2 tumour, PSA 10-20 ng/ml, Gleason score 7
- High risk = T3 tumour, PSA 20-50 ng/ml, Gleason score 8
Regional or distant metastases =
- T4/N1/M1 tumour, PSA ≥50 ng/ml
Analyses were adjusted for a range of potentially confounding factors, including:
- family history of prostate cancer
- vigorous physical activity
- body mass index
- marital status
- history of vasectomy
- history of PSA testing
What were the basic results?
Over follow-up, a total of 3,839 cases of prostate cancer were diagnosed. Frequency of ejaculation per month decreased with age. The proportion of men reporting average frequency of 13 or more ejaculations per month was 57% aged 20-29 but dropped to 32% at age 40-49.
Excluding men with erectile dysfunction, compared with men who ejaculated four to seven times per month:
- There was a 20% decreased risk of prostate cancer for those who ejaculated 21 times or more per month aged 20-29, (adjusted hazard ratio (aHR) 0.80, 95% confidence interval (CI) 0.69 to 0.92).
- There was an 18% decreased risk of prostate cancer in ages 40-49 for those who ejaculated 21 times or more per month, (aHR 0.82, 95% CI 0.70 to 0.96).
- There was a 26% reduction in risk of prostate cancer for men aged over 50 who had ejaculated 21 times or more per month in the previous year, (aHR 0.74, 95% CI 0.58 to 0.94).
- There was also a decreased risk of prostate cancer in ages 40-49 for those who ejaculated 13-20 times per month (aHR 0.81, 95% CI 0.72 to 0.90).
- There were similar yet smaller reductions in risk at all ages for men ejaculating 13 or more times per month.
For men ejaculating over 13 times per month compared with four to seven times per month:
- For ejaculation while aged 20-29, there was a 25% lower risk of getting "low risk" prostate cancer, (aHR 0.75, 95% CI 0.63 to 0.89).
- For ejaculation while aged 40-49, there was a 28% lower risk of getting "low risk" prostate cancer, (aHR 0.72, 95% CI 0.61 to 0.83).
- For ejaculation in the year before the questionnaire, while aged over 50, there was a 25% lower risk of getting "low risk" prostate cancer, (aHR 0.75, 95% CI 0.62 to 0.92).
- For ejaculation aged 20-29, there was a 27% lower risk of getting "intermediate risk" prostate cancer (aHR 0.73, 95% CI 0.61 to 0.88).
- No significant differences were found for ejaculation frequency at older ages and "intermediate risk" cancer, or for any age and "high risk" prostate cancer.
How did the researchers interpret the results?
The researchers concluded that "this large prospective study provides the strongest evidence to date of a beneficial role of ejaculation in prevention of prostate cancer".
They add that "more frequent ejaculation in the absence of risky sexual behaviours could represent an important means of reducing the profound medical costs and physical and psychological side effects of unnecessary diagnosis and treatment of low-risk tumours, even though it appears to be less strongly associated with aggressive disease".
This research showed an association between ejaculating more frequently and a lower chance of getting prostate cancer in three different age groups.
Before too much is read into these findings, there are some limitations of the research to consider:
- Three age groups were looked at; ages 20-29, 40-49 and 50 and over. It is not known what the differences are within these groups and it is not known what the outcomes would be if ejaculation was measured in different age categories.
- Although the authors adjusted for some variables, there are still some factors that might have influenced the results, such as sociodemographic background, education level and whether the men had children.
- The circumstances of ejaculation were not considered – in other words whether the occurrences were mostly through masturbation or with a sexual partner. This might have had an influence on the results.
- The questionnaire relied on self-reporting and considering past history, which may have led to recall bias where participants inaccurately reported their ejaculation history.
- Prostate cancer was self-reported through medical history and not specifically screened for. It might be that men who are more sexually active are less likely to seek cancer screening and therefore may be unaware of the presence of prostate cancer.
- The study was conducted on mostly white health professionals in the US and might not be generalisable to the entire UK male population – especially as prostate cancer tends to be more common in men of African-Caribbean or African descent.
Aside from ejaculating frequently, other methods that may help reduce your risk of prostate cancer include achieving or maintaining a healthy weight, and regular exercise.
Analysis by Bazian
Edited by NHS Website
Links to the headlines
Mail Online, 5 July 2017
The Sun, 5 July 2017
Links to the science
European Urology. Published online March 28 2016