Abstract
Prostate cancer is one of the most common malignancies worldwide, with an estimated 400,000 new cases diagnosed annually. Its incidence and mortality have been associated with milk or dairy product consumption in international and interregional correlational studies. As a result, case-control and cohort studies have further investigated this association and are described in this review. Of 12 case-control studies, six found significant associations, as did five of 11 cohort studies, with relative risk of prostate cancer among those with the most frequent dairy product consumption ranging between 1.3 and 2.5, with evidence of a dose-response relationship. Mechanisms that may explain this association include the deleterious effect of high-calcium foods on vitamin D balance, the tendency of frequent dairy intake to increase serum insulin-like growth factor I (IGF-I) concentrations, and the effect of dairy products on testosterone concentration or activity.
Conclusions
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 A pooled analysis of cohort studies showed that the adjusted relative risk of incident breast cancer for women consuming two to five drinks (30-60 grams of alcohol) per day was 1.41 (95% CI, 1.18-1.69).45 In a 1997 review by the World Cancer Research Fund and the American Institute for Cancer Research, six of 11 cohort studies and 15 of 36 case-control studies found such an association.46
http://www.cancerproject.org/survival/cancer_facts/prostate_dairy.php--------
Milk and the Cancer Connection On January 23, 1998 researchers at the Harvard Medical School released a major study providing conclusive evidence that IGF-1 is a potent risk factor for prostate cancer. Should you be concerned? Yes, you certainly should, particularly if you drink milk produced in the United States.
IGF-1 or insulin-like growth factor 1 is an important hormone that is produced in the liver and body tissues. It is a polypeptide and consists of 70 amino acids linked together. All mammals produce IGF-1 molecules very similar in structure and human and bovine IGF-1 are completely identical. IGF-1 acquired its name because it has insulin-like activity in fat (adipose) tissue and has a structure that is very similar to that of proinsulin. The body's production of IGF-1 is regulated by the human growth hormone and peaks at puberty. IGF-1 production declines with age and is only about half the adult value at the age of 70 years. IGF-1 is a very powerful hormone that has profound effects even though its concentration in the blood serum is only about 200 ng/mL or 0.2 millionth of a gram per milliliter (1-4).
The bottom line
Despite assurances from the FDA and industry-paid consultants there are now just too many serious questions surrounding the use of milk from cows treated with synthetic growth hormone to allow its continued sale. Bovine growth hormone is banned in Australia, New Zealand and Japan. The European Union has maintained its moratorium on the use of rBGH and milk products from BST-treated cows are not sold in countries within the Union. Canada has also so far resisted pressure from the United States and the biotechnology lobby to approve the use of rBGH commercially. In light of the serious concerns about the safety of human consumption of milk from BST-treated cows consumers must maintain their vigilance to ensure that European and Canadian governments continue to resist the pressure to approve rBGH and that the FDA in the United States moves immediately to ban rBGH-milk or at least allow its labeling so that consumers can protect themselves against the very real cancer risks posed by IGF-1.
(The last reference is from a site that also wants to sell you supplements. - DG)
