The Extent of Hormones in Meat


If I were to reel off the names, Estradiol, Testosterone, Progesterone, Zeranol, Trenbolone, Progestin melengestrol acetate, some of you may know some of these are powerful anabolic steroids, many of which are commonly used in bodybuilding. What if I also told you that all of these are also fed to the cows which you eat the meat from on a daily basis!* Should you be concerned? What if I also told you this is just to make the cattle grow faster so that the we can meet demands of meat supply. It doesn’t cover the various xenobiotics to ensure the cattle stay alive long enough to produce these sufficient quantities of meat. Can these get into our bodies and if so what affect are they having?

Why do we have these hormones and antibiotics in our meat?

Throughout history, regardless of industry in order to grow efficiency must be taken into consideration. Nothing can be wasted and any opportunities to improve areas are almost always taken. In agriculture, natural selection only allowed breeders to grow cattle, poultry and swine to a certain size. The next stage in the efficiency cycle is the introduction of hormones and antibiotics. To put into perspective, the scale of antibiotics use in the US has 80% of all antibiotics manufactured for sole use in agriculture.

What does each hormone do?

estraiolEstradiol: This is natural female sex hormone which is produced in the early stages of ovulation. It’s purpose is to act a growth hormone for the tissue in the reproductive regions. It’s not only found in females, it’s also present in males and is a product of aromatase in testosterone formation. Studies show that high levels of estradiol cause infertility in men¹. Its use in cattle is to enhance the fertility of the cattle so that it’s easier to breed livestock thus making the farms more productive.

Testosterone: This is a natural male sex hormone that is used in anabolic growth. This is used as a steroid to increase the rate of muscle growth so that cattle can be put to slaughter faster, again…efficiency.

Progesterone: This is a sterone and it’s used to regulate the menstrual cycle, upon removal of a progesterone the previously suppressed gonadotropin-releasing hormone causes luetinising hormone production to surge which in turn causes an massive increase in ovulation and pregnancy can occur.

Zeranol: This is a natural compound called a mycotoxin and it’s a non steroidal estrogen agonist and it’s used in conjunction with the other hormones to increase muscle mass. In vitro this has been shown to increase cell proliferation in breast cancer cells.²

Trenbolone: Trenbolone is used as an implant and is a powerful anabolic steroid. It’s helps promote growth and stimulate appetite so that the cattle eat enough to grow at a optimal rate. This steroid is very popular amongst bodybuilders.

Progestin melengestrol: This is added to cattle feed and is a more effective form of progesterone which has low bioavailability when administered orally.

How these affect us?

These hormones and steroids in meat can affect us in two ways, directly and indirectly. The direct affect is that from consumption of the meat itself and indirectly through contamination of water sources. 

Pregnant woman are most at risk, many of these hormones are fat soluble and can be stored and their concentrations built up over time. The added oestrogen’s in the meats can in increase the likelihood of infertility in male offspring. Developing girls are at risk because zeranol which suppresses estrogen causes growth rate abnormalities with slower rates of breast development as well as a potential breast cancer risk.²

For males the main risk is infertility, this is often a secondary trait as a result of mothers ingesting the hormones which affects the development of the fetus in particular the reproductive organs. A study4 showed that children from mothers who had a high beef diet had sperm counts 24% less than those with what was considered a low beef diet. 

Other concerns are that we do not know what affect these chemicals and their metabolites do when they interact with other chemicals we’re exposed to. Check out our post on other additives added to our food

Remember eat organic!

*Assuming you live in the United States, if you’re in Europe you will not be consuming these hormones as they are banned and antibiotics are tightly controlled because they were unable to find a limit to how much would be deemed safe.³

¹Raman, JD; Schlegel, PN (2002). “Aromatase inhibitors for male infertility”. The Journal of Urology167 (2 Pt 1): 624–9
² Zhong S1, Ye W, Lin SH, Liu JY, Leong J, Ma C, Lin YC., Anticancer Res. 2011 May;31(5):1659-65.
³ European commission, Scientific Committee on Veterinary Measures Relating to Public Health. (1999). Assessment of potential risks to human health from hormone residues in bovine meat and meat products. Retrieved Nov. 21, 2012.
4Semen quality of fertile US males in relation to their mothers’ beef consumption during pregnancy. Hum Reprod. 2007 (6):1497-502.

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