A Practically Primal Perspective on Conventional Beef, Part 1: Hormones

7/13/11 update:  I decided that I don't want to endorse or appear to endorse the use of any meat produced by conventional methods of feeding the livestock grains, primarily corn and soybeans.  Since animals consume 80% of the grain and soy produced by U.S. agriculture, this system drives the ongoing destruction of our topsoil both through crops and through grazing.  Animal food production consumes 87% of all freshwater used in the U.S. each year, and thus is the primary driver of depletion of water reserves.  This system also produces most of the water pollution occurring in the U.S.  Our conventional livestock production system has enormous costs detailed in this article from Cornell University.  Since I have known of these costs for more than 20 years, I feel embarrassed and remorseful that I wrote this series and other articles that endorsed the use of conventional animal products.  I served as part of a system that promotes a completely unsustainable approach to human nutrition. 

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Some people wonder if one can safely eat conventional meat as a part of a practically paleo lifestyle.   Documentary films like Food Inc, along with a plethora of anti-meat, pro-vegetarian literature, have given people the impression that conventional meat products come from inhumane production systems and that conventional meat contains hazardous amounts of hormones, antibiotics, and pesticide residues.  Shall we believe this?  Let’s take a look, starting with hormones.

Hormones

Does conventional meat contain hazardous levels of hormones?  Short answer:  No.  For details, read on.

First, a primal perspective.

I once had a native African explain to me that among her people, they have a taboo against hunting female animals.   This taboo makes a lot of sense for a tribe dependent on hunting.  If you kill a female, you are eliminating a bunch of potential offspring at the same time; while killing a few bulls will have essentially no effect on the fecundity of the herd. 

So hunters would have preferred eating bulls to cows, and in Europe still today some producers  raise bulls.  Similarly, in the U.S. we get most of our beef from steer—neutered bulls—while we save the cows for calving and milk production.  

Bulls and steer differ hormonally.  Bull meat samples tested by Fritsche and Steinhart [1] contained medians of 0.34 mg/kg testosterone and 0.32 mg/kg epitestosterone, while steer meat samples (from unsupplemented steers) contain medians of 0.01 mg/kg testosterone and 0.12 mg/kg epitestosterone.   Bull meat had up to 1.05 mg/kg testosterone.  Thus, bull meat contains a median of 34 times more testosterone and more than twice as much epitestosterone than steer meat; and bull meat might have up to 105 times as much testosterone as a steer.

Their data indicates that at least some of the meat typically eaten by hunter-gatherers would have had  between eight and one hundred times more endogenous steroid hormone—in the form of testosterone— than an untreated modern “organic” steer.  Thus, it would seem that through evolution humans adapted to consumption of meat containing considerably greater levels of steroid hormone than what we find in a modern untreated or “organic” steer meat.

Since testosterone promotes muscle tissue growth, a steer has much less growth potential than a bull.  However, testosterone also makes bulls aggressive and harder to handle, so we can more easily control steers.  Modern husbandry attempts to restore the growth potential without the aggression by substituting for a small amount of the lost testosterone other anabolic but less androgenic steroids, primarily estrogens.

Currently the FDA allows the use of five hormones in cattle for meat production: progesterone, testosterone, estradiol-17β, zeranol, and trenbolone acetate.

The first three are natural hormones, the same as produced by an intact animal.   Zeranol occurs naturally also,  produced by fungi.   It acts as a non-steroidal estrogen agonist, meaning it acts like estrogen. Trenbolone acts as an androgenic steroid that promotes muscle growth.

Does the use of these in raising cattle result in meat or dairy products with unusually high, potentially harmful levels of dietary estrogens or other steroids? 

According to Doyle [2], four studies have found that muscle meat from an untreated steer provides estrodiol in a range of 2.8-14.4 pg/g.  Two other studies found estrodiol at concentrations of 12 pg/g in liver, and 12.6 pg/g in kidney.   Doyle also cites an FAO report finding that meat from implanted steers had 9.7 pg/g estrodiol at 15 days after implantation, and 7.3 pg/g at 61 days after implantation.  In short, the levels of estrodiol in hormone-treated meat falls in the normal range found in meat from untreated cattle.  Doyle comments:

“Estradiol levels in edible tissues of implanted cattle are usually significantly higher than in controls but the increases are small, in the ng/kg range. The greatest increases reported in an FAO report on estradiol residues were 0.002, 0.0065, 0.005, and 0.0084 mg/kg for implanted bulls, steers, heifers, and calves, respectively. These increases are well below the FDA recommended limits listed in the table on p. 2 and well below estradiol concentrations in muscles of pregnant heifers (0.016 to 0.033 mg/kg).”

Similarly, Hartmann, Lacorn, and Stienhart examined the “Natural occurrence of steroid hormones in food.” [3]  Using gas chromatography-mass spectrometry, they measured the levels of twelve steroids occurring in market-sourced meats, milk products, plants, yeast, and alcoholic beverages, including both naturally occurring and residues of additional hormones used in production.  They tested beef (bull, steer, heifer), veal, pork, poultry, eggs, fish, and plants (potatoes, wheat, rice, soybeans, haricots beans, muschrooms, olive oil, safflower oil, and corn oil). 

They found no significant difference in hormone levels between meat from hormone-treated and untreated animals.  In the typical diet, meat, poultry, and eggs proved to supply less hormones than non-paleo milk products :

“Meat does not play a dominant role in the daily intake of steroid hormones. Meat, meat products and fish contribute to the hormone supply according to their proportion in human nutrition (average about one quarter). The main source of estrogens and progesterone are milk products (60-80%). Eggs and vegetable food contribute in the same order of magnitude to the hormone supply as meat does.”

Thus, if you eat a paleo diet, and avoid milk products, you actually would eliminate the greatest dietary source of estrogens, and might reduce your total dietary intake of estrogens by more than 50%.

As for health effects of these hormones in foods, Hartmann et al compared the intake of hormones from diet from all sources to natural human hormone production levels, concluding that the food contents of steroids are insignificant compared to endogenous production [p. 18]:

“These values [amounts provided by diet] are far exceeded by the human steroid production (Table 10). Children, who show the lowest production of steroid hormones, produce about 20 times the amount of progesterone and about 1000 times the amount of testosterone and estrogens that are ingested with food on average per day. It has further to be taken into consideration that about 90% of the ingested hormones are inactivated by the first-pass-effect of the liver.  This leads to the conclusion that no hormonal effects, and as a consequence no tumor promoting effects, can be expected from naturally occurring steroids in food.”

For example, a prepubertal boy, most vulnerable to adverse effects of excess dietary estrogens,  produces about 100 micrograms of estrogen daily.  Beef muscle meat contains less than 0.02 micrograms of estrogens per kilogram.  To get from beef an intake of estrogens equal to just one percent of his endogenous estrogen production, i.e. 1 microgram, he would have to consume 50 kilograms--110 pounds-- of beef in a day!  

According to Doyle [2], the lowest observed effect level of exogenous estrogen is 5 micrograms of estrogens per kilogram of body weight.  Thus, a 40 kg prepubertal boy would have to consume 200 micrograms of estrogens daily to observe an effect.  To get this from conventional hormone-treated beef, he would have to consume 10,000 kg of beef every day.  Clearly he isn't going to get feminized by eating beef.

Opponents of the use of hormones in modern animal husbandry often claim that the use of hormones in production of meat and dairy products causes early puberty, obesity, and cancer in modern industrial nations.

Cornell University has a website discussing these Consumer Concerns About Hormones in Foods:

Can steroid hormones in meat affect the age of puberty for girls?
Early puberty in girls has been found to be associated with a higher risk for breast cancer. Height, weight, diet, exercise, and family history have all been found to influence age of puberty (see BCERF Fact Sheet #08, Childhood Life Events and the Risk of Breast Cancer). Steroid hormones in food were suspected to cause early puberty in girls in some reports. However, exposure to higher than natural levels of steroid hormones through hormone-treated meat or poultry has never been documented. Large epidemiological studies have not been done to see whether or not early puberty in developing girls is associated with having eaten growth hormone-treated foods.

A concern about an increase in cases of girls reaching puberty or menarche early (at age eight or younger) in Puerto Rico, led to an investigation in the early 1980s by the Centers for Disease Control (CDC). Samples of meat and chicken from Puerto Rico were tested for steroid hormone residues. One laboratory found a chicken sample from a local market to have higher than normal level of estrogen. Also, residues of zeranol were reported in the blood of some of the girls who had reached puberty early. However, these results could not be verified by other laboratories. Following CDC's investigation, USDA tested 150 to 200 beef, poultry and milk samples from Puerto Rico in 1985, and found no residues of DES, zeranol or estrogen in these samples.

In another study in Italy, steroid hormone residues in beef and poultry in school meals were suspected as the cause of breast enlargement in very young girls and boys. However, the suspect beef and poultry samples were not available to test for the presence of hormones. Without proof that exposure to higher levels of steroid hormones occurred through food, it is not possible to conclude whether or not eating hormone-treated meat or poultry caused the breast enlargement in these cases.

Can eating meat from hormone-treated animals affect breast cancer risk?
Evidence does not exist to answer this question. The amount of steroid hormone that is eaten through meat of a treated animal is negligible compared to what the human body produces each day. The breast cancer risk of women who eat meat from hormone-treated animals has not been compared with the risk of women who eat meat from untreated animals.

Similarly, we don't have any studies of comparing the prostate cancer risk of men who eat meat from hormone-treated animals to men who eat meat from untreated animals.

In Hyperinsulinemic Diseases of Civilization:  More Than Just Syndrome X, Cordain, Eades, and Eades [4] point out that current evidence actually implicates high carbohydrate intake as the promoter of these hormone-related disorders, because high carbohydrate intake raises insulin levels which increases levels of insulin-like growth factors and increases endogenous production of steroids, by far the main source of steroid exposure, while reducing sex hormone-binding globulins that reduce steroid activity. In the abstract they summarize:

Specifically, hyperinsulinemia elevates serum concentrations of free insulin-like growth factor-1 (IGF-1) and androgens, while simultaneously reducing insulin-like growth factor-binding protein 3 (IGFBP-3) and sex hormone-binding globulin (SHBG). Since IGFBP-3 is a ligand for the nuclear retinoid X receptor a, insulin-mediated reductions in IGFBP-3 may also influence transcription of anti-proliferative genes normally activated by the body’s endogenous retinoids. These endocrine shifts alter cellular proliferation and growth in a variety of tissues, the clinical course of which may promote acne, early menarche, certain epithelial cell carcinomas, increased stature, myopia, cutaneous papillomas (skin tags), acanthosis nigricans, polycystic ovary syndrome (PCOS) and male vertex balding. Consequently, these illnesses and conditions may, in part, have hyperinsulinemia at their root cause and therefore should be classified among the diseases of Syndrome X. [Italics added]

Using the paleo principle to evaluate this claim, we should expect ill effects of hormones in meat to appear in heavy meat-eating hunter-gatherer groups since they ate meat from intact animals, particularly bulls having 10 times as much testosterone as domesticated animals.

Alas for the hormone hypothesis, hunter-gatherers eating strictly native foods had no obesity, and, so far as we can tell, no cancer. [5]  Further, in The Paleolithic Prescription, S. Boyd Eaton, M.D., Melvin Konner M.D., Ph.D., and Marjorie Shostak present data on reproductive milestones among recent hunter-gatherers.  Among three recent hunter-gatherer tribes (Agta, !Kung, Ache), the average age of menarche (onset of menses) is about 16 years of age, compared to 12.5 years in the U.S. according to Wikipedia.

Since hunter-gatherers eating bull meat on a regular basis and consuming around 50% of energy from meat had none of the problems attributed to hormones in meat, it seems unlikely that hormones in meat can account for cancer or any other hormone-related problem in modern people.

I prefer to see people eat meat from animals not treated with hormones or hormone analogues, but if for budget reasons you choose to eat conventional meat (hormone treated or not) instead of grass fed, I think you don't need to worry that its hormone content will harm you in any way.  You should worry more that by avoiding the meat, you will consume too many carbohydrates that will much more profoundly alter your endocrine system in harmful directions.

But before you get meat from hormone-treated animals, check to see if you can find a supplier for meats from animals raised on typical feeds (corn, soy, etc.) but without added hormones.  In Phoenix, we have at least two markets--Sprouts and Sunflower--that supply meat that comes from such animals.
These markets sell their meats at prices comparable and sometimes lower than what I see at more conventional supermarkets where the meat comes from hormone-treated animals.

We will look at antibiotics and other issues in upcoming posts.

Thanks to Matt Schoeneberger, co-author of S.P.E.E.D. Weight Loss Book, for help accessing one of the articles I used as a reference for this article.  

Notes:

1. Fritsche S and Steinhart H. Differences in natural steroid hormone patterns of beef from bulls and steers.  J. Anim. Sci. 1998. 76:1621–1625.  Full text: jas.fass.org/cgi/reprint/76/6/1621.pdf

2.  Doyle E.  Human Safety of Hormone Implants Used to Promote Growth in Cattle:

A Review of the Scientific Literature.  Food Research Institute, University of Wisconsin

Madison, WI 53706.  Full text:  fri.wisc.edu/docs/pdf/hormone.pdf

3.  Hartmann S, Lacorn M, and Stienhart H. Natural occurrence of steroid hormones in food. Food Chemistry 62(1);7-20 

4.  Cordain L, Eades M, Eades M.  Hyerinsulinemic diseases of civilization: More than just syndrome X.  Comparative Biochemistry and Physiology Part A 136 (2003) 95–112.  PDF available here.

5.  Stefanson, V. Cancer:  Disease of Civilization.