After giving a very long, in-depth essay of myriad studies relating dairy consumption and prostate cancer in men, The Cancer Project (headed up by Neal D. Barnard, M.D.) gives us this conclusion:
"Evidence from international, case-control, and cohort studies suggests that men who avoid dairy products are at lower risk for prostate cancer incidence and mortality, compared with others. In case-control and cohort studies, the relative risk of prostate cancer among subgroups with the most frequent milk consumption, compared with those at the lowest consumption levels, falls in the range of 1.3 to 2.5. These findings raise two important questions: Does the observed relationship represent cause and effect, and is available evidence sufficient to justify a recommendation that milk-drinking men alter their dietary habits?
Findings supporting a cause-and-effect relationship include the relative consistency of this association in diverse populations, evidence of a dose-response relationship, plausible biological mechanisms that underlie the observed associations, and no reasonable alternative explanation for these findings. Perspective is lent to the second question by a comparison with evidence linking alcohol use and breast cancer risk. Although somewhat fewer studies have addressed the association between milk and prostate cancer, their demonstrated effect, strength, and consistency of evidence approach those relating alcohol to breast cancer risk, an association that is now widely accepted and incorporated into the Dietary Guidelines for Americans.44"
Okay, so if we have all these powerful studies linking dairy products to prostate cancer, why don't we see the Dietary Guidelines for Americans changed to suit what we know? Or why have most Americans never heard of said correlation? (To see all the research quoted for the above conclusion, read href="http://www.cancerproject.org/diet_cancer/diet/prostate_dairy.php">.)
Perhaps because that would be bad for business?