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A Needless New Risk of Breast Cancer

Los Angeles Times, March 20, 1994


The Food and Drug Administration recently warned dairy producers, distributors and retailers against "hormone-free" labels on milk from cows that have not been given the biotech milk-production stimulant known as recombinant bovine growth hormone. The FDA states that such labeling could be "false or misleading" under federal law, as there is "no significant difference between milk from treated and untreated cows." Monsanto, maker of the hormone, is already suing one large Midwest milk producer for using the label.

The confusing FDA guidelines were, according to the consumer publication Daily Citizen, written by Deputy Commissioner Michael Taylor, a former counsel for Monsanto and a biotech umbrella organization. The guidelines are scientifically flawed and reckless and reflect flagrant disregard of consumers' right to know. Furthermore, the FDA ignores evidence linking milk from treated cows with increased risk of breast cancer. The concerns, based on published research:

  • The biotech hormone induces a marked and sustained increase in levels of insulin-like growth factor-1, or IGF-1, in cow's milk.
  • IGF-1 regulates cell growth, division and differentiation, particularly in infants. While human and normal bovine IGF-1 are identical, they are largely bound to protein and thus probably less biologically active than the unbound IGF-1 in treated milk.
  • IGF-1 is not destroyed by pasteurization or digestion and is readily absorbed across the intestinal wall. In a 1990 FDA publication disclosing toxicity tests conducted by Monsanto, feeding the hormone (trade name Posilac) to mature rats for only two weeks resulted in statistically significant increases in body and liver weights and bone length. These effects were seen at a small fraction of injected doses given to control rats. But by gerrymandering these explicit data, the FDA alleged that IGF-1 "lacks oral toxicity."
  • Neither the FDA nor Monsanto has investigated the effects of long-term feeding of IGF-1 and treated milk on growth, or on more sensitive sub-cellular effects in infant rats or infants of any other species.

Cows injected with the biotech hormone show heavy localization of IGF-1 in breast (udder) epithelial cells; this does not occur in untreated cows.

  • IGF-1 induces rapid division and multiplication of normal human breast epithelial cells in tissue cultures.
  • It is highly likely that IGF-1 promotes transformation of normal breast epithelium to breast cancer.
  • IGF-1 maintains the malignancy of human breast-cancer cells, including their invasiveness and ability to spread to distant organs.
  • The breast tissues of female fetuses and infants are sensitive to hormonal influences. Imprinting by IGF-1 may increase future breast-cancer risks and sensitivity of the breast to subsequent unrelated risks such as mammography and the carcinogenic and estrogen-like effects of pesticide residues in food, particularly in premenopausal women.

These concerns are not new. In a 1989 letter to the FDA, I warned that the effects of IGF-1 "could include premature growth stimulation in infants, [breast enlargement] in young children and breast cancer in adult females." More recently, the Council on Scientific Affairs of the American Medical Association stated: "Further studies will be required to determine whether the ingestion of higher-than-normal concentrations of bovine insulin-like growth factor is safe for children, adolescents, and adults." The opposite of "further study" is uncontrolled, unlabeled sales of treated milk to unwitting consumers.

Apart from risks of breast cancer and other IGF-1 effects, the FDA and industry have down-played additional differences between hormonal and non-hormonal milk. The FDA- approved label insert for Posilac, a pamphlet that only dairy farmers see, admits that its "use is associated with increased frequency of use of medication in cows for mastitis and other health problems." Monsanto's own data further show up to an 80% incidence of mastitis, an udder infection, in hormone-treated cattle and resulting contamination of milk with statistically significant levels of pus; this will necessitate virtually routine use of antibiotics, with attendant risks of allergic reactions and antibiotic resistance.

Congress should insist that, at the very least, the FDA immediately revoke its restrictions on labeling of milk from untreated cows. More prudently, it should ban the use of these hormones.


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