Added Hormones in Meat and Dairy
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Added Hormones in Meat and Dairy

Do They Affect Health; and If So; How?

Hormones in meat image According to one 2000-2003 survey by the Food Marketing Institute (a supermarket trade association), one-fifth of American shoppers are not confident that food is safe, and of those, 40% are concerned about hormones in food. Still, American consumers are more confident than their European counterparts. Hormonal additives are entirely illegal in the European Union (EU), as well as in Canada, simply based on the biologic plausibility of health implications, alongside some scant laboratory and animal research. The EU has gone so far as to ban the import of US beef and dairy from treated animals, spurring a small tariff war between them and the US.

So what’s this debate all about? Why do some people suspect hormonal additives are unhealthy? Are their suspicions founded? Here’s the science behind the scare.

The Culprits: Hormone Additives

Hormones are powerful, naturally produced chemical messengers that control vital behaviors in all plants and animals. Ergo, they are present in all animal products whether or not the animals have been treated with hormone supplements.

Hormones Used in Livestock

Six steroid hormones are currently approved for use in US livestock to speed lean muscle growth. Both the Food and Drug Administration (FDA) and a joint committee of the Food and Agricultural Organization and World Health Organization (FAO/WHO) deemed residues of these additives in meat safe for consumption in 1988. Three of the approved additives are synthetic versions of steroid hormones that occur naturally in both cows and humans: estrogen, testosterone, and progesterone; the other three are synthetic variations that closely mimic these. More than 90% of US livestock are currently injected with these hormones, which can increase production of veal and beef by up to 15%.

Hormones Used in Dairy Cattle

In 1993, the FDA and a National Institutes of Health (NIH) panel of experts approved the use of recombinant (ie, genetically engineered) bovine growth hormone (rbGH). This protein hormone promotes increased milk production as opposed to muscle growth. Its approval came only after extensive review of available data by said organizations that showed the milk of treated dairy cattle to be safe.

Today, somewhere from 5%-30% of dairy cattle receive rbGH; those that do produce at least 10% more milk than other cows. As opposed to cattle raised as livestock, no steroid hormones are approved for use in dairy cattle.

Suspected Health Concerns

Too much or little of any hormone can be harmful to the body, and in severe cases can result in an endocrine disorder such as diabetes or hypothyroidism . Additionally, certain cancers are known to be responsive to some hormones in the steroid class. Estrogen is listed as a known carcinogen (most associated with uterine cancer , followed by breast cancer ), and progesterone as “reasonably anticipated to be” a carcinogen, in an updated report by the National Toxicology Program at the Department of Health and Human Services.

Concerns Over Additives in Beef

While taking steroid hormones at high doses, such as in hormonal replacement therapy, has been shown to increase risk for some cancers, the amount present in meat products is comparably miniscule. Indeed, the FDA argues that residues of additives in beef are negligible in comparison to levels that occur naturally both in cows and humans.

Authorities also point out that steroid hormone levels in beef, whether from treated animals or not, are far lower than those found in eggs or milk. Additionally, these levels are dwarfed by high levels of plant estrogens—or “phytoestrogens”—present in soybeans, wheat germ, cabbage, broccoli, and many other vegetables. Phytoestrogens have also been shown to be hormonally active in people.

One lesson from history may largely explain the continued wariness toward hormonal additives even at reportedly negligible doses. The synthetic estrogen hormone, diethylstilbestrol (DES), that was used beginning in the 1950s to fatten cattle and chickens, as well as to prevent miscarriages in women, was found to increase cancer risk in humans. Its use in food production was phased out by 1979, several years after it was pronounced to be a known carcinogen. Receiving ample media coverage, the DES misfortune peaked awareness of the potential dangers of chemical additives in both food and drugs.

Besides cancer risk, a few other unsubstantiated claims against steroid additives have been made. For example, they have been blamed at least partially for earlier puberty onset in some female populations (also a risk factor for breast cancer), but no epidemiological studies have ever been done on this.

Concerns Over Additives in Dairy

As for dairy hormones, critics of rgBH, such as the Consumer Union and the Cancer Prevention Coalition, argue that milk from treated cows contains higher levels of this hormone than milk from non-treated cows. However, rgBH is not recognized as a hormone in the human body, and even if it were, as a protein hormone it is broken down into metabolites in the stomach (unlike steroid hormones, which do pass into the bloodstream when ingested orally), so any health risk is biologically unlikely.

But, more importantly, critics contend that the milk also contains higher levels of insulin-like growth factor-1 (IGF-1), a protein hormone that is identical in cows and humans. IGF-1 plays an important role in milk production, bone growth, and cell division. Indeed, Eli Lilly & Co., a manufacturer of rbGH, reported a ten-fold increase in IGF-1 levels in milk of cows receiving the hormone. And while IGF-1 is naturally present in humans, new research does suggest that elevated levels are associated with breast, colon, and prostate cancers. The Harvard-based Nurses’ Health Study found higher blood levels of IGF-1 in women with breast cancer than in those without. Still, no research has been done to show if drinking milk with higher levels of IGF-1 translates to higher blood levels of IGF-1.

An Undetermined Verdict

For now, no conclusive evidence exists either to support or totally refute the purported health risks from consuming meat or dairy from hormonally treated cows. Studies that compare long-term morbidity between people who consume products of treated cattle and people who don’t will be essential to closing the debate on their questionable healthfulness.

Until more rigorous research is done, some might prefer to err on the side of caution. Among authorities that do advise caution, most say that pre-pubescent children are at greatest risk, since their bodies naturally contain lower levels of hormones than adults, and they tend to consume more milk, if not beef, per unit of body weight. Pregnant women may also want to use caution. Here are some tips if you want to keep treated products off your or your family members’ plate:

  • Buy certified organic meat and meat products: Organic animals can only be fed 100% organic feed and cannot be given antibiotics or growth hormones. It’s also safe to buy imported European meat products, as added growth hormones are banned in the EU.
  • Buy rBGH-free or certified organic milk and dairy products: Organic dairy farms don’t allow the use of rBGH, and other companies that don’t use rBGH often include this information on the label. It’s also safe to buy imported European and Canadian cheeses and other dairy products, as rbGH is banned in these countries.


Council for Biotechnology Information

The Organic Farming Research Foundation

US Food and Drug Administration


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Cancer Prevention Coalition. Milk: America’s health problem. Available at: . Accessed on February 9, 2005.

Cornell University Program on Breast Cancer and Environmental Risk Factors in New York State (BCERF). Consumer concerns about hormones in food (No. 37). Available at: . Accessed on February 6, 2005.

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Organic Consumers Association (OCA). rBGH (rBST) [press release]. July 3, 1997. Available at: . Accesses on February 10, 2005

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US Food and Drug Administration. The use of steroid hormones for growth promotion in food-producing animals. Available at: . Accessed on February 3, 2005.

Last reviewed January 2007 by Lawrence Frisch, MD, MPH

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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