Today’s factory-farmed meat is full of synthetic hormones (80-90% of feedlot cattle are administered growth-enhancing hormones, including estrogens, androgens, and progestins). The androgens include steroids such as melengestrol acetate, zeranol, testosterone propionate, and trenbolone acetate; the estrogens include estradiol. To give you an idea of how disruptive these chemicals can be, the runoff of feedlot steroids into streams has been linked with fish in those streams changing sex (male fish being feminized into female fish).
Why is this relevant to girls? Meat consumption has been directly linked with early onset puberty in girls, particularly in the U.S., which consumes more meat per capita than any other nation (see map: http://chartsbin.com/view/12730). The age of puberty has been dropping as meat consumption has increased over time – and particularly since factory farming was introduced in the 1980s.
In 1950, a British study benchmarked the earliest puberty for girls at 11.5 years. By 1997, a U.S. study found that the earliest signs of puberty had fallen to 9.9 years among white girls and 8.9 years among African-American girls. A Danish study found that puberty onset dropped by a year between 1991 and 2006, from 10.8 years to 9.8 years.
A direct link between the amount of meat in the diet and early puberty was found in a 2010 study. About half the girls eating more than 12 portions of meat a week at the age of seven started their periods by age 12 ½, compared with only 35% of those who ate fewer than four portions of meat weekly. The more meat they ate, the earlier they tended to reach puberty.
Early onset puberty is associated with an increased risk for hormonally-related cancers. The National Cancer Institute identifies a risk factor for breast cancer as “an early age at first menstrual period” (before age 12). It is also associated with increased mortality rate. A 2009 CDC study found that women with ovarian cancer are 51% more likely to die of it if they entered puberty before age 12 than if they entered puberty at age 14 or older.
A plant-based diet is one option for concerned parents. Another option is organic meat, which does not carry the risks associated with synthetic hormones.
For further reading:
Hutchins, S. (2007). Assessing Potential for Ground and Surface Water Impacts from Hormones in CAFOs. Presentation by the Ground Water & Ecosystems Restoration Division of the Environmental Protection Agency at the EPA Office of Research & Development CAFO workshop in Chicago, Illinois, August 21, 2007. http://www.epa.gov/ncer/publications/workshop/pdf/hutchins_ord82007.pdf
Hylton, W. (2015). A Bug in the System: Why last night’s chicken made you sick. The New Yorker, February 2, 2015. http://www.newyorker.com/magazine/2015/02/02/bug-system
Kolpin, D.W. et al. (2002). Pharmaceuticals, hormones, and other organic wastewater contaminants in U.S. streams, 1999-2000: A national reconnaissance. Environ. Sci. Technol. 36(6): 1202-1211. doi/pdf/10.1021/es011055j
Neill, F. (2010). Puberty Blues. Intelligent Life Magazine, June 29, 2010. http://moreintelligentlife.com/print/2815.
Raloff, J. (2002). Hormones: Here’s the Beef: environmental concerns reemerge over steroids given to livestock. Science News. 161(1): January 5, 2002, p10.
Robbins, C. et al. (2009). Influence of Reproductive Factors on Mortality after Epithelial Ovarian Cancer Diagnosis. Cancer Epidemiol Biomarkers Prev. July. 18: 2035. doi: 10.1158/1055-9965.EPI-09-0156.
Rogers, I. et al. (2010). Diet throughout childhood and age at menarche in a contemporary cohort of British girls. Public Health Nutrition. 13: 2052-2063. doi: 10.1017/S1368980010001461.
Vajda, A. et al. (2008). Reproductive Disruption in Fish Downstream from an Estrogenic Wastewater Effluent. Environ. Sci. Technol. 42 (9): 3407–3414. http://pubs.acs.org/doi/abs/10.1021/es0720661