Dear Michael,

I appreciate your pointing out that studies that conclude that the frequency of sex can reduce prostate cancer risks are contradictory and therefore inconclusive. Still, your conclusion that sexually transmitted disease may account for the connection between frequent sex and lowering one's risk for prostate cancer does not ring true. Here’s why:

(1) None of the studies you've referenced on sexual frequency and prostate cancer appear to raise sexually transmitted diseases as a factor leading to prostate cancer. Yet you've jumped to that conclusion based on other studies that don't appear to discuss sexual frequency. You need to point to additional studies that focus on both frequency and STI's , if there are any. Otherwise your conclusion is a big "leap".
(2) You stated that studies that sample more men are more likely to be valid than studies that look at a smaller number of men, and you stress that the studies with a larger population point to lowering prostate cancer risk.
My question is: Doesn't frequent sex imply greater likelihood of exposure to infectious diseases? Your conclusion therefore seems illogical - unless the studies you mention actually track subjects in terms of disease and also in terms of married versus unmarried men (one versus many partners), which you did not state and need to clarify.
(3) None of the studies you've mentioned are scientific, since there is no way to do a double-blind study in which a group of men in their twenties are randomly assigned to two groups: "abstainers/celebates" - meaning infrequent ejaculation over the years, or none at all; versus "studs", meaning frequent ejaculation from ages 20 through 60(by means of intercourse or masturbation).I elaborate further about this on my blog, ConquerProstateCancer.com., in reference to a major Australian study you didn't mention. Based on this journalists and others have incorrectly encouraged frequent sex or masturbation in order to lower prostate cancer risk. All such studies are inherently flawed.

Apart from this, as a prostate cancer survivor, I feel it's important to cite more recent overall statistics as I've mention in my book, Conquer Prostate Cancer: How Medicine, Faith, Love and Sex Can Renew Your Life. I refer here to NCI's projection that the annual number of men who get prostate cancer is no longer 230,000, but was about 186,000 last year, and is projected to be 193,000 during 2009 (37,000 less than you've noted).

In addition the number of those who die is no longer 30,000 a year but 28,600 last year and a projected 27,000 or so in 2009 (3,000 less than you stated). The current statistics on prostate cancer incidents and deaths are bad enough without citing higher numbers that were true three or more years ago.
--Rabbi Ed Weinsberg, Ed.D., D.D.

My figures on prostate cancer incidence came from the American Cancer Society Website. If they're off by a few thousand, that doesn't change the fact that this is a major cancer for men, approximately as prevalent as breast cancer in women.

You say that none of the studies I cited are "scientific" because it's impossible to assign men to abstain or be sexually active. You are correct that researchers cannot perform gold-standard studies of prostate cancer risk: randomized, double-blind, placebo-controlled (RDBPC) trials. However, the observational studies I cited are still scientifically valid, as far as they go. They were all published in the peer-reviewed medical literature. Observational studies may not be RDBPC, but they can still provide insights.

In 500-word blog posts, it's impossible to delve very deeply into medical/sexual research. Your criticisms are well taken. But I stand by my feeling that sex/ejaculation is more likely to be protective than to raise risk. Thank you for your comment.