BREAST CANCER, RBGH AND MILK
BREAST CANCER, RBGH AND MILK
A study of U.S. women published in the LANCET links insulin-like growth factor-1 (IGF-1) with breast cancer. Earlier this year a study linked IGF-1 to prostate cancer. Prostate and breast cancers are major killers of men and women in the U.S. and in other industrialized countries. IGF-1 levels are now being artificially increased in much of the cows' milk being sold throughout the U.S. These new cancer studies raise serious questions about the wisdom of allowing IGF-1 levels to be raised in milk.
The latest study found a 7-fold increased risk of breast cancer among pre-menopausal women younger than age 51 with the highest levels of IGF-1 in their blood. The prostate cancer study published in SCIENCE in January, 1998, found a 4-fold increase in risk of prostate cancer among men with the highest levels of IGF-1 in their blood. Thus IGF-1 in blood is associated with larger relative risks for common cancers than any other factor yet discovered.
It is not clear from these studies whether IGF-1 causes these cancers, or whether elevated IGF-1 accompanies some other factor that causes these cancers. At the very least, researchers are hoping that measurements of IGF-1 will identify individuals at high risk of getting these cancers, so that surveillance might be increased. (However, it would be common practice in the U.S. for people under such surveillance to find their health insurance canceled, which tends to discourage participation in surveillance programs.)
IGF-1 is a powerful naturally-occurring growth hormone found in the blood of humans. Dairy cows injected with genetically-engineered bovine growth hormone (rBGH) give milk containing elevated levels of IGF-1, and the IGF-1 in milk can pass into the blood stream of milk consumers. Cows' IGF-1 is chemically identical to that in humans. Ingested IGF-1 would ordinarily be broken down in the stomach, but the presence of casein in milk prevents such breakdown. Thus these latest cancer findings raise important public health questions about the safety of milk from cows treated with bovine growth hormone (rBGH).
rBGH is injected into cows to extend by several weeks their period of lactation, and thus to force them to produce more milk. rBGH is not needed in any way because U.S. dairy cows already produce such an excess of milk that the U.S. government spends more than $200 million each year purchasing surplus milk, a subsidy to the milk industry. Because rBGH injections can cause numerous ill effects in cows, veterinarians in Germany have refused to administer rBGH to cows on grounds that it violates their professional code of ethics, which forbids intentional harm to animals. U.S. veterinarians have not taken a similar stand.
CONTINUED ON NEXT PAGE --> Written by: Peter Montague
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