During this year’s annual meeting of the American Urological Association in New Orleans, researchers affirmed what may be the first modifiable risk factor for prostate cancer: ejaculation.

A modifiable risk factor refers to the risks people can prevent through healthy habits, such as diet and exercise. Most of the risk factors for cardiovascular disease, for example, are modifiable; the Centers for Disease and Control Prevention (CDC) reported healthy habits could prevent at least 200,000 of the deaths caused by heart attack and stroke. But for something like prostate cancer, the risks stem more from individual genes and family history.

A 2004 JAMA study was among the first to suggest a modifiable risk factor, finding “high ejaculation frequency” may be associated with lower risk for prostate cancer. The present research builds upon these findings with the “high quality data” collected from nearly 32,000 men participating in the Health Professionals Follow-up study; the men were followed for a total of 18 years.

At the start of the study, men aged 20 to 29 and 40 to 49 were asked to calculate the average number of times they ejaculated per month, including the number of times they ejaculated during the previous year. Researchers then used both averages to compute a lifetime average.

The results showed men who ejaculated at least 21 times a month reduced their risk for prostate cancer by 20 percent compared to men who ejaculated four to seven times a month. Although Dr. Jennifer Rider, an epidemiologist at the Harvard T.H. Chan School of Public Health in Boston, said “we shouldn’t dwell on the numbers, but instead should focus on the dose-response relation.”

Rider added these findings have “three outstanding strengths:” it’s prospective, versus the usual retrospective; it’s the largest cohort, or long-term study done on this relationship; and it gets specific about ejaculation. It is further evidence safe sex may improve prostate health.

The Science of Orgasm, written by Barry R, Jinusayrjm Carlos Beyer-Flores, and Beverly Whipple, cited research from the late 70s that found mortality risk was 50 percent lower among men who had frequent orgasms (two or more per week), even when controlling for other factors such as age and smoking.

But how exactly could ejaculation protect against cancer? The orgasm itself has protective benefits, Dr. Rider said. Research shows the hormones oxytocin and dehydroepiandrosterone (DHEA) are released during orgasm; oxytocin has the power to lower blood pressure in women, reducing their risk for cardiovascular disease at the same time, while DHEA has been linked to lower risk for breast and cervical cancer.

Although breast cancer is rare in men, BBC reported, Greek resarchers found men who had fewer than six orgasms per month were significantly more likely to develop breast cancer. Additionally, increased levels of DHEA have been shown to improve memory, boost brain function, as well as also lower risk for cardiovascular disease. So these chemicals released during orgasm, not so much ejaculation itself, could account for improved health.

It’s important to note frequent ejaculation was associated with incident prostate cancer, not risk for what researchers consider lethal prostate cancer. The National Cancer Institute defines incidence rate as “the number of new cancers of a specific type occurring in a specified population during a year.” This rate does not include recurrence.

Prostate cancer is the second most common form of cancer among American men. The American Cancer Society estimates there will be about 220,800 new cases in 2015, with about 27,540 deaths from prostate cancer. It can be serious, but a diagnosis isn’t a death sentence; more than 2.9 million men in the U.S. who have been diagnosed are still alive today.

Source: American Urological Association Annual Meeting. 2015.