Asked in Cattle Diets and Nutrition
How do hormones in cattle affect humans?
There is not enough adequate, unambiguous research and studies to show if any level of hormone from beef or dairy affects humans. Such controversy over whether hormones given to beef and dairy cattle affect humans is less scientific and more consequential, theoretical and philosophical. The primary reason that the EU banned use of hormones in livestock was out of concern for the welfare of animals, not the ill-effects on the health of humans.
The American Cancer Society is even unsure about the effects of IGF-1 from milk products has any effect on cancer rates in humans. Many other reputable sources state the same about beef consumption. Studies about beef consumption in humans in relation to semen production in men or rate of puberty in young girls were too ambiguous, as they failed to state where the beef samples originated from: commercial feedlot, or natural grass-finishing operation? Such is what can be easily seen in the Organic Consumers Association report on the claim that growth hormones from beef cattle "damage" human health, if you look for such pertinant and crucial information.
Besides what is listed in the related links below, a search on "hormones in cattle affect humans" using your favorite search engine will give you similar results.
As far as estrogen from beef playing a role in breast and ovarian cancer, a study from Oxford university (link provided below) shows much ambiguousness as mentioned above. The cancer patients where such results were obtained had a remarkably unknown history of diet, body type, age, family history, exposures to certain carcinogens, and many other factors that may influence incidence to ovarian and/or breast cancer.
Additionally, there are many sources that dictate how high various plant sources are in estrogen concentration, compared with beef. As an example, a 3 oz. steak from a beef steer that has been implanted contains only 1.9 nanograms of estrogen, whereas a 3 oz. serving of soybean oil contains 138,000,000 ng of estrogen.