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American Milk: Colon and Breast Cancer Risks

American dairy farmers use rBGH hormone to increase milk production

  • rBGH increases cancer risk of milk
  • Citizen advocacy groups escalate efforts against rBGH

Study Warns of Colon and Breast Cancer Risks from rBGH Milk

January 23, 1996, Washington, DC - The Cancer Prevention Coalition and Food & Water, released a study today reporting that milk from cows injected with recombinant Bovine Growth Hormone (rBGH) increases risks of breast and colon cancers in humans. This study is published in the January issue of the International Journal of Health Services, a peer-reviewed, leading international public health journal.

The study summarizes evidence that rBGH increases levels of insulin-like growth factor (IGF-1) in milk. IGF-1 is a powerful stimulator and regulator of cell-growth and division in humans and cows. The study concludes that increased IGF-1 levels are risk factors for breast and colon cancer.

rBGH poses an even greater risk to human health than ever considered," warned Samuel Epstein M.D., Professor of Environmental Medicine at the University of Illinois School of Public Health and Chairman of the Cancer Prevention Coalition, author of the new report. "The FDA and Monsanto have a lot to answer for. Given the cancer risks, and other health concerns, why is rBGH milk still on the market?"

Since 1986, independent scientists have expressed concern about the lack of research on the potential health effects of IGF-1 in rBGH milk. More recently, the Council of Scientific Affairs of the American Medical Association admitted that: "Further studies will be required to determine whether the ingestion of higher than normal concentrations of bovine IGF-1 is safe."

Increased IGF-1 levels in rBGH milk exert their cancer promoting effects directly on cells lining the colon, and on breast cells, following absorption into the blood.

" Monsanto 's claims that rBGH is perfectly safe have been proven dead wrong today. This study further validates the health concerns of millions of consumers about this controversial product," said Michael Colby, Executive Director of Food and Water. "Only Monsanto is benefiting from this drug. It's time for dairy companies to side with consumers by adopting a policy that they will not allow rBGH, under any circumstances, to be used by their farmers."

Epstein concluded, "The entire nation is currently being subjected to a large-scale adulteration of an age-old dietary staple by a poorly characterized and unlabeled biotechnology product which is very different than natural milk."

Statement by the Cancer Prevention Coalition on IGF-1 and Breast and Colon Cancer

The FDA has ignored the wide range of converging evidence that associates increased consumption of insulin growth factor-i (IGF- 1), which increases in milk from rBGH treated cows, with a potential risk of breast and other types of cancer.

Published research shows that rBGH use on dairy cows induces a marked and sustained increase in levels of insulin-like growth factor-1, or IGF-1, in cow’s milk. This is admitted by FDA (Juskevich & Guyer, 1990), and more explicitly by others (Prosser 1988; Prosser 1989; Mepham, 1992). A recent admission by another manufacturer of rBGH (Eli Lilly & Co.) reports a ten fold increase in IGF-1 levels. Furthermore, there is suggestive evidence that IGF- 1 in rBGH milk is more bioactive than in non-hormonal milk (Mepham, 1992).

IGF-1 regulates cell growth, division and differentiation, particularly in children. Human and normal bovine IGF-1 are identical, they are largely bound in protein and thus probably less biologically active than unbound IGF1 in rBGH derived milk.

IGF-1 is not destroyed by pasteurization. In fact this process substantially increases IGF-1 levels in milk. (Juskevich and Guyer, 1990). Nor is IGF-1 destroyed by digestion. Moreover, FDA admits that IGF-1 is readily absorbed across the intestinal wall (Juskevich & Guyer, 1990); this was also previously admitted by Monsanto in 1987. Further confirmation is also provided by other authorities (e.g. Mepham, 1992). Additionally, recent research indicates that IGF-1 can be absorbed into the bloodstream where it can effect other hormones. (Donovan and Odle, 1994)

FDA and other industry sources have not published any detailed studies on the oral toxicity of IGF-1 Rather, they have consistently refused to make available their findings and raw data. A highly condensed summary of an IGF- 1 Monsanto short term test in mature rats was released by FDA (Juskevich & Guyer, 1990). The agency alleges that this study confirms IGF- 1's "lack of oral activity." At the outset it should be noted that the Monsanto test was contracted out to Hazelton Laboratories, which has a two decade history of misrepresentation of scientific data. (Epstein, 1978). However, even the cited Monsanto/Hazelton data explicitly reveal statistically significant evidence of growth promoting effects. Feeding relatively low doses of IGF-1 to mature rats for only two weeks resulted in statistically significant and biologically highly significant systemic effects: increased body weight; increased liver weight; increased bone length; and decreased epiphyseal width. These results are confirmatory of prior theoretical predictions.

The FDA has failed to investigate the effects of long-term feeding of IGF- 1 and rBGH-milk on growth, or on more sensitive sub-cellular effects, in infant rats or infants of any other species.

Significantly, cows injected with rBGH show heavy localization of IGF-l in breast (udder) epithelial cells; this does not occur in untreated cows. (Furlanetto, et al, 1984; Gregor, et al, 1985; Campbell, et al, 1986.) 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 cancers. (Furlanetto, et al, 1984; Harris, et al, 1992, growth factors such as IGF-1 "are responsible at least in part for the evolution of normal breast epithelia to breast cancer...'). Moreover, IGF-1 maintains the malignancy of human breast cancer cells, including their invasiveness and ability to spread to distant organs. (Lippman, 1991, 1993). IGF-l has been similarly associated with colon cancer (Tricolo, et al, 1986).

The undifferentiated pre-natal and infant breast is particularly susceptible to hormonal influences. (Ekbom, et al. 1992) Such imprinting by IGF-1 may increase future breast cancer risks, and may also increase the 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 pre-menopausal women. (Elwood, et al, 1993).

Concerns about increased levels of IGF- 1 in milk from cows treated with rBGH are not new. In 1990, the National Institutes of Health (NIH) Consensus panel on rBGH expressed concerns on adverse health effects of IGF-1 in rBGH milk, calling for further study on the treated milk's impacts, especially on infants. (NIH, 1991). 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." (AMA, 1991). Instead of further study, the FDA allowed for uncontrolled, unlabeled sales of treated milk to unwitting consumers.

Given the potential health impacts of consumption of milk and other dairy products derived from rBGH treated cows, all such products at a minimum be labeled so that consumers are aware of what they are purchasing and consuming. More prudently the FDA approval of rBGH should be withdrawn until the agency performs adequate long term testing on the impacts of increased levels of IGF- 1 in milk and other dairy products derived from rBGH treated cows.

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Donovan, S.M. and Odle J., 1994. Growth Factors in Milk as mediators of Infant development. Annual Review of infant development. Annual Review of Nutrion, 14:147-67.

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Glimm, D .R. et al. Effect of bovine somatropin on the distribution of immunoreactive insulin like growth factor-i in lactating bovine mammary tissue. J. Dairy Sci. 1988:71:2923-2935.

Gregor, P. and Burleigh, B.D. Presence of high affinity somatomedin/insulin-line growth factor receptors in porcine mammary gland. Endocrinol. 116 (suppl. 1, Abstract) :223, 1985.

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Harris, J.R. et al. Breast Cancer. NEJM 1992:7;473-480

Juskevich, J.C., Guyer, C.G. (FDA). Bovine growth hormone food safety evaluation. Science 1990:249:875-884.

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Mepham, T.B. Public health implications of Bovine somatotropin use in dairying: discussion paper. J. Royal Soc. Medicine 1992:85:736-739

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Prosser, C.G. Bovine somatotropin and milk composition. The Lancet November 19, 1988:1201

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Source: Press Conference, National Press Club, Washington D.C., January 23, 1996

Samuel S. Epstein, M.D.
Chairman, Cancer Prevention Coalition
c/o University of Illinois at Chicago
School of Public Health, M/C 922
2121 W. Taylor Street
Chicago, IL 60612

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