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Hormone Growth Promoters Fed to Beef Cattle Linked to Adverse Impacts on Male Sexual Development
Almost all beef cattle entering feedlots in the United States are given hormone implants to promote faster growth. The first product used for this purpose - DES (diethylstilbestrol) - was approved for use in beef cattle in 1954. An estimated two-thirds of the nation's beef cattle were treated with DES in 1956 (Marcus, 1994, cited in Swan et al., 2007).
Today, there are six anabolic steroids given, in various combinations, to nearly all animals entering conventional beef feedlots in the U.S. and Canada:
- Three natural steroids (estradiol, testosterone, and progesterone), and
- Three synthetic hormones (the estrogen compound zeranol, the androgen trenbolone acetate, and progestin melengestrol acetate).
Anabolic steroids are typically used in combinations. Measurable levels of all the above growth-promoting hormones are found at slaughter in the muscle, fat, liver, kidneys and other organ meats. The Food and Drug Administration has set "acceptable daily intakes" (ADIs) for these animal drugs.
Questions and controversy over the impacts of these added hormones on human development and health have lingered for four decades. In 1988 the European Union banned the use of all hormone growth promoters. The ADIs on the books for years are based on traditional toxicity testing methods and do not reflect the capacity of these drugs, which are potent endocrine disruptors, to alter fetal and childhood development. According to Swan et al. (2007) -
"...the possible effects on human populations exposed to residues of anabolic sex hormones through meat consumption have never, to our knowledge, been studied. Theoretically, the fetus and the prepubertal child are particularly sensitive to exposure to sex steroids..."
This gap in research is remarkable, given that every beef-eating American for over 50 years has been exposed to these hormones on a regular basis. To begin to explore possible impacts, Swan et al. (2007) carried out a study assessing the consequences of beef consumption by pregnant women on their adult male offspring. The families included in the study were recruited from the multicenter "Study for Future Families" (SFF).
The study team assessed sperm quantity and quality among 773 men. Data on beef consumption during pregnancy was available from the mothers of 387 men. These mothers consumed, on average, 4.3 beef meals per week, and were divided into a high beef consumption group (more than seven meals per week) and a low-consumption group (less than 7 per week).
The scientists compared sperm concentrations and quality among the men born to women in the high and low beef consumption groups. They found that:
- Sperm concentration (volume) was 24.3 percent higher in the sons of mothers in the "low" beef consumption group.
- Almost 18 percent of the sons born to women in the high beef consumption group had sperm concentrations below the World Health Organization threshold for subfertility - about three-times more than in the sons of women in the low consumption group.
The authors concluded that -
"These findings suggest that maternal beef consumption is associated with lower sperm concentration and possible subfertility, associations that may be related to the presence of anabolic steroids and other xenobiotics in beef."
This study lends urgency to the long-recognized need for the FDA to reconsider the acceptable daily intakes of hormones used to promote growth in beef feedlots. This reassessment will, in all likelihood, be resisted by the animal drug and beef industries, and once begun, will take many years to be carried out. In the interim, families wanting to avoid the risk of developmental problems in their male children can do so by choosing organic beef.
Source: "Semen quality of fertile US males in relation to their mothers' beef consumption during pregnancy"
Authors: S.H. Swan, F. Liu, J.W. Overstreet, C. Brazil, and N.E. Skakkebaek
Journal: Human Reproduction, Advance Access published online March 28, 2007. Access the Full Text here.