This is interesting. There is a new study – you can read more here showing that frequent ejaculation reduces prostate cancer risk in men.
“risk for prostate cancer was 20% lower in men who ejaculated at least 21 times a month than in men who ejaculated 4 to 7 times a month. The 20% risk reduction was seen at ages 20 to 29 and 40 to 49, and for the lifetime average (P trend < .0001 for all)”.
This was observational study shows that the man who have more ejaculations per month have generally less chances of having prostate cancer. This does not tell us that increasing the number of ejaculations reduces this risk. The data is quite interesting so I recommend reading.