Hormones which are intended for occasional therapeutic use are injected into young animals such as calves to fatten them faster. Like athletes taking steroids, this practice results in "fast flesh", but the side effects are unclear. Some single out specific hormone levels and combinations as dangerous to human consumers, while others insist that any hormone additive is potentially dangerous. Practically, it is an open question whether beef raised with no hormones at all can compete with the quality and market price of beef raised with some hormones, although consumers are now reacting against the flabby, tasteless quality of "hormone-plumped up" meat.
The practice of using hormones to improve the growth rates of animals and reduce the fat content of the meat became fashionable during the 1970s, when farmers found they could cut costs as well as satisfy consumer demand for leaner meat.
Bovine stromatotrophin (BST) is a synthetic, genetically engineered substance based on a naturally occurring bovine growth hormone and injected into dairy cows to increase production of milk. The hormone has been widely criticized for its detrimental effects on animal welfare and could pose a health hazard to those who drink the milk. Whilst widely used in the USA, Canadian and European resistance to the use of the hormone hinges in part on the failure to agree on an international standard for use. The sale and marketing of BST has been banned in the European Union since 1990. The moratorium expired at the end of 1999 but a renewal was requested from the EU Council of Ministers.
Milk from cows treated with recombinant bovine growth hormone (rBGH in the US, rBST in Europe) has significantly elevated levels of IGF-I (insulin-like growth factor-I), a growth factor responsible for a wide variety of biological functions. In addition, the IGF-I in the milk of rBGH-treated cows is potentially more bioactive than the naturally occurring form, and this bioactivity may be increased further by pasteurization. Children may be particularly vulnerable to adverse effects, because of their rapid growth rate and their more permeable intestinal tract. In addition, other segments of society may also be at an increased risk, such as those with celiac disease, Crohn's disease, autism, cirrhosis, cow's milk allergy and people taking certain medications.
The hormones 17beta-oestradiol, progesterone, testosterone, zeranol, trenbolone and melengestrol acetate (MGA) promote growth in cattle. According to a 1999 European Commission report, these hormones have adverse developmental, neurobiological, genotoxic and carcinogenic effects on people who consume them, either via the parent compound, or via metabolites. 17beta-oestradiol both initiates and promotes cancerous tumours. Prepubertal children are at the greatest risk. Growth hormones have been banned in the European Union since 1988. However, many banned substances continue to enter from South America and eastern Europe. Organized crime controls the traffic throughout Europe with production sources through chemical companies and the pharmaceutical industry.
Hormones banned in the EEC/EU are held by some farmers to be necessary to the production of high-quality beef at competitive prices. At a time of beef surplus, the EEC/EU banned all hormones, reputedly to discourage farmers from producing beef. There is not a fundamental conviction among farmers in the EEC/EU that the total ban is necessary or economically viable, and this makes the ban difficult to enforce, however needed it may be for public health reasons. In 1999, the USA was using threat of prohibitive tariff protection on European imports if Europe does not drop its restrictions on hormone treated beef exports from the USA. It called the arguments against use of hormones "phony science".
Stilbene oestrogens used in animal production as anabolic agents are orally active, persist in food, pose environmental problems because of their low biodegradability. Diethyl stilbesterol (DES) is a known carcinogen. On reaching adolescence, the children of mothers who had taken DES in pregnancy were developing cancer, the girls in the vaginal tract and the boys in the prostate, bladder or testicles. Sometimes the cancer showed as early as seven, sometimes as late as the mid-twenties. Abnormalities showed in 1978 in Milan in children who were fed veal which had been treated with DES. Knowledge of the toxicology of many other used substances is still rudimentary.