Twenty-one a month, followed for eighteen years
The largest study of its kind found the frequent end of the scale did better.
Nearly 32,000 men in the American Health Professionals Follow-up Study reported how often they ejaculated and were then followed for eighteen years. Men reporting 21 or more ejaculations a month had roughly a fifth lower risk of a prostate cancer diagnosis than men reporting four to seven.
It is an observational study, it cannot prove which way the arrow points, and the authors say so. Healthier men may simply have more sex. What it does rule out is the opposite claim, repeated for two centuries: there is no sign in this data that frequent ejaculation harms the prostate.
What to do with it
This is not a prescription, and no urologist would write one from an observational study. Treat it as the reassurance it is: there is no documented harm on this side of the scale.
What is worth acting on is the ordinary screening advice for your age, and any change in urinating, blood, or persistent pain, which belongs with a doctor the same week rather than in a search box.
