Both chapter 5 of Wiley and Allen as well as the blog post “When I was Your Age” spoke of the declining age at which puberty begins. Wiley and Allen’s text attributes this to consumption of higher-energy foods and access to health care (128). While this is probably a large factor in the trend of decreasing age, I have always heard that growth hormones in commercially produced animal products (notably chicken) are, at least to some degree, responsible for this. Further, I have heard that these hormones affect females more than males, furthering the young age at which puberty begins in females.
Joel Fuhrman mentions in his Huffington Post article that there was a decline in the age of puberty from the early Twentieth Century until the 1960s when the trend leveled out. Further, he states that the mid-1990s began to see another decline in the age of the first menarche. Despite this, the two online resources I used remain inconclusive as to the effects of animal hormones as well as the causes of the early onset of puberty. Fuhrman goes on to list multiple potential causes for the decline in menarche age including childhood overweight and obesity, diets providing low nutrition, increasing levels of intake of animal protein, and exposure of endocrine-disturbing chemicals (EDCs) (Fuhrman). An article hosted by Cornell University states that in the US only six steroid hormones are used legally in meat production. Of these, three are naturally produced sex hormones. Further, these steroid hormones are only legally used in cattle and sheep. The article lists two cases of reported effects of animal growth hormones on human consumers, however these remain inconclusive. In one, USDA and independent lab results differed and in the second the meat was not available for testing. The article does state that the amounts of the three non-sex steroid hormones are subject to limits set by the USDA (Gandhi).
While it seems that there has not been conclusive evidence that the levels of hormones currently legally allowed within the United States have major effects on health (including the age of first menarche/onset of puberty), the potential risks of the early onset of puberty, including increased risk of breast and ovarian cancer as well as cardiovascular disease, necessitates further study of the issue (Allen 129, Fuhrman)
Fuhrman, Joel, M.D. "Girls' Early Puberty: What Causes It, And How To Avoid It." The Huffington Post. N.p., n.d. Web. <http://www.huffingtonpost.com/joel-fuhrman-md/girls-early-puberty_b_857167.html>.
Gandhi, Renu, and Suzanne M. Snedeker. "Consumer Concerns About Hormones in Food." Cornell University. N.p., n.d. Web. <http://envirocancer.cornell.edu/factsheet/diet/fs37.hormones.cfm>.