Ejaculation Frequency and Prostate Cancer Risk: What the Evidence Actually Shows

最終更新日： 8月 25, 2026

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Prostate cancer is among the commonest cancers diagnosed in men, and most of the cancers found are slow-growing. It causes no symptoms in its early stages, which is why it is looked for with a blood test rather than waiting for something to go wrong. Men understandably want to know whether anything they do can lower their risk — and one particular study gets quoted more than any other in answer.

It is worth looking at properly, because it is more interesting and considerably weaker than the headlines suggest.

What the study found

A large prospective cohort study from the United States, published in 2016, followed nearly 32,000 men for eighteen years and asked them how often they ejaculated in their twenties and again in their forties.

• Typical frequency in the group was around 8 to 12 times a month.
• Men reporting 21 or more times a month had a modestly lower rate of prostate cancer than men reporting the least.
• The association was seen for low- and intermediate-risk disease.
• No association was seen with aggressive, high-risk cancer — the form that causes almost all the deaths.

Why this is not the same as a preventive measure

An earlier version of this article carried a caveat in the text saying the evidence was observational — and then answered yes, frequent ejaculation reduces prostate cancer risk in its own FAQ. The two contradicted each other, and the FAQ has been corrected. That matters, because the FAQ is the part search engines quote.

Three specific problems sit between this association and any claim of cause and effect:

• Sexual frequency travels with everything else. Men who ejaculate more often tend to be healthier, more likely to have a partner, less depressed, and to have higher testosterone. Any of those could be doing the work, and no statistical adjustment fully separates them.
• Cause and effect may run backwards. Prostate disease reduces sexual function years before it is diagnosed. Some of the men in the lowest-frequency group may have had low frequency because of an undetected prostate problem, rather than developing one because of low frequency.
• What it counts is diagnoses, not disease. The association concerns the low-risk cancers that are largely found by screening — many of which would never have harmed anyone. A difference in how often such cancers are detected is not the same as a difference in how often men get ill.

The most telling point is the last line of the findings. Whatever the association represents, it does not touch aggressive prostate cancer — which is the only kind that determines whether a man lives or dies of this disease.

So what should a man take from it?

Something reassuring, and not a target. There is no reason to think a normal sex life carries any prostate risk, and this study is decent evidence that it does not — a question men genuinely worry about and are often too embarrassed to ask. That is worth saying plainly.

What it is not is a number to hit. Treating 21 a month as a prescription reads far more into observational data than it can carry, and a man who cannot reach it has not failed at anything. An earlier version of this article presented the figure as actionable advice; it is better understood as a description of the group in whom the association was strongest.

The factors with better evidence behind them for cancer outcomes generally remain the dull ones — not smoking, keeping weight down, staying active — and they act on heart disease at the same time, which is what will actually kill most men. See also diet and prostate cancer, 、および what the evidence on lycopene really supports.

And about screening

Nothing described here changes the screening question, and the earlier version of this article overstated it by presenting PSA testing as a routine part of a health check for men over fifty.

Whether to have a PSA test is a decision, not a default. It depends on age, family history, ethnicity, general health, and — most of all — on what a man would want done with an abnormal result, since PSA testing leads to biopsies and to the detection of cancers that would never have caused trouble. It is a conversation worth having properly rather than a box to tick. That discussion is set out in should I have a PSA test.

Symptoms that need assessment regardless

None of the above applies to a man who already has symptoms. In an emergency in Thailand, call 1669.

• Visible blood in the urine or in the semen.
• New bone pain, particularly in the back, hips or ribs.
• Unexplained weight loss.
• Inability to pass urine with a painful full bladder — this needs same-day treatment.
• A PSA result you have been given and do not understand. Bring the number itself and any previous readings.

お客様からよくいただくご質問

Does frequent ejaculation reduce the risk of prostate cancer?

It has not been shown to. A large observational study found that men reporting the highest ejaculation frequency developed low- and intermediate-risk prostate cancer somewhat less often, but an association of that kind cannot establish cause and effect — sexual frequency travels alongside general health, partnership and testosterone, and early prostate disease itself reduces sexual activity years before diagnosis. An earlier version of this article answered this question with a plain yes, which was too strong.

Is 21 times a month a target I should aim for?

No. That figure describes the group in whom the association was strongest in one study; it is not a prescription and there is no evidence that reaching a particular count changes anything. A man whose frequency is lower has not done anything wrong.

Does it protect against aggressive prostate cancer?

No association was found with high-risk disease — which is the form responsible for almost all deaths from prostate cancer. This is the single most important limitation of the finding.

Should I have a PSA test?

That is a decision to make deliberately rather than a routine part of a health check. It depends on your age, family history, general health and what you would want done with an abnormal result, because PSA testing leads to biopsies and to finding cancers that would never have caused harm. An earlier version of this article presented it as a routine recommendation for men over fifty, which has been corrected.

Is there any prostate risk from a very active sex life?

There is no evidence of harm, and this study is reasonable reassurance on that point. Men ask about it far more often than they admit, and the answer is that a normal sex life at any frequency is not a prostate risk.

相談の手続きをする

For a PSA discussion or prostate assessment, Dr. Soarawee Weerasopone sees patients at バンコク病院本部 そしてチョンブリー県のサミティベート・シーラチャ病院にて 088-022-1445. Bring every previous PSA result with its date — the trend over time says more than any single number.

バンコク病院の遠隔医療は、来院が困難な患者様（海外からの患者様を含みます）を対象にご利用いただけます。泌尿器科宛てに事前にメールでご手配ください。 bhquro@bdms.co.th. サミティベート・シラチャは対面診療のみです。料金に関するお問い合わせは当ウェブサイトではなく、病院にお問い合わせください。.

免責事項 この記事の内容は、バンコク病院本社（Bangkok Hospital Headquarters）の認定泌尿器科医であるソラウィー・ウィーラソポン医師（Dr. Soarawee Weerasopone）が執筆および監修したものであり、教育目的のみを意図しています。これは医学的なアドバイス、診断、または個別の処方ではなく、個人的なメッセージングチャンネルやソーシャルメディアを通じてアドバイス、診断、処方が行われることはありません。ソラウィー医師は公開のソーシャルメディアアカウントを運営していません。彼の名前で個人的な相談を提供しているアカウントはすべて詐欺です。タイで緊急事態が発生した場合は、以下にお電話ください。 1669.