Zeranol Use in Meat and Breast Cancer

In 1979, an epidemic of breast enlargement was noted in Italian children. Poultry or veal was suspected, given that estrogens may be fed to farm animals to accelerate their weight gain. After this episode, Europe banned the use of anabolic growth promoters in agriculture, and has banned the importation of American meat from animals injected with drugs like Zeranol, sold as Ralgro Magnum.

Zeranol is the one of the most potent known endocrine disruptors—100,000 times more estrogenic than the plastics chemical, BPA, for example. And Zeranol constitutes a special case among potential endocrine disruptors, because in contrast to all other estrogenic “endocrine-disrupting” chemicals, Zeranol is present in human food, because it’s deliberately used—in fact, designed to be a potent, persistent, estrogen, whereas the estrogenic properties of the other chemicals are accidental.

And if you drip blood from a cow that’s been implanted with the drug on human breast cancer cells in a petri dish, you can double the cancer growth rate. We don’t drink blood, though, but preliminary data also showed that muscle extracts, meat extracts, also stimulated breast cancer cell proliferation.

Furthermore, Zeranol may cause the transformation of normal breast cells into cancer cells in the first place. Zeranol-containing blood from implanted cattle was capable of transforming normal human breast cells into breast cancer cells within 21 days.

Obese women may be at greater risk of developing Zeranol-induced breast cancer, since they already have high levels of leptin, a hormone produced by fat cells, that can itself promote breast cancer growth. And Zeranol exposure can greatly enhance this growth-promoting action. This result also suggests that Zeranol may be more harmful to obese breast cancer patients than to normal weight breast cancer patients, in terms of breast cancer development.

In conclusion, because these anabolic growth promoters in meat production are, by far, the most potent hormones found in human food, we should really be testing people, especially children, before and after eating this meat. It amazes me that it hasn’t been done, and until it has, we have no idea what kind of threat they may pose—though the fact that Zeranol is as potent as estradiol—the primary sex steroid in women and DES—should concern us. DES is another synthetic estrogen marketed to pregnant women—all pregnant women until 1971, when it was shown to cause vaginal cancers in the daughters. But few know it was also used in meat.

In the absence of effective federal regulation, the meat industry uses hundreds of animal feed additives, with little or no concern about the carcinogenic and other toxic effects of dietary residues of these additives. Illustratively, after decades of misleading assurances of the safety of DES and its use as a growth-promoting animal feed additive, the United States finally banned its use some 40 years after it was first shown to be carcinogenic. The meat industry then promptly switched to other potentially carcinogenic additives, such as Zeranol.

When girls started dying from vaginal cancer, DES-treated meat was subsequently banned in Europe. However, misleading assurances, including the deliberate suppression of residue data, managed to delay a U.S. ban on DES in the meat supply for eight years.

Today, virtually the entire U.S. population consumes, without any warning, labeling, or information, unknown and unpredictable amounts of hormone residues in meat products over a lifetime. If all hormonal and other carcinogenic feed additives aren’t banned immediately, the least we could have is “explicit labeling requirements of the use and of [hormone] residue levels in all meat products, including milk and eggs.”

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Katie Schloer.

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• H Leffers, M Naesby, B Vendelbo, N E Skakkebaek, M Jørgensen. Oestrogenic potencies of Zeranol, oestradiol, diethylstilboestrol, Bisphenol-A and genistein: implications for exposure assessment of potential endocrine disrupters. Hum Reprod. 2001 May;16(5):1037-45.

Permission kindly granted by Dan Piraro at Bizarro.com for the cartoon

• animal products
• body fat
• breast cancer
• cancer
• carcinogens
• children
• dairy
• eggs
• endocrine disruptors
• estrogen
• Europe
• fat
• feed additives
• food additives
• hormones
• industry influence
• leptin
• meat
• milk
• obesity
• poultry
• pregnancy
• vaginal cancer
• women's health