The answer: more than 20(!), according to this study of over 3,000 men out of Montreal, Canada -- but only if they're female. (Apparently, having more than 20 male sexual partners is associated with an increased risk of prostate cancer.) Although this is just a correlation, it's certainly interesting. And if it's not the number of sexual partners that reduces prostate cancer risk, but something else these ladies men have in common, we definitely want to know what that is! But, meanwhile, do
