By Meghan Anderson Thomas

The age of menarche has decreased significantly in the past century, from an average age of 16-17 years old to younger than 13 years of age (Buttke, Sircar, & Martin, 2012). There are several different theories as to why this may be occurring. Some believe that environmental toxins or exposure to estrogen-disrupting compounds (EDC) may play a role. EDCs are found in household plastics, cleaners, deodorizers and personal care products. Other theories include increased body mass index in children and adolescents. Increased hormones found in obese children maybe responsible for the earlier onset of puberty. Finally, nutritional implications such as breast versus bottle-feeding and increased dairy and meat intake in adolescence may also play a role in puberty at younger ages.

EDCs include benzophenones, dichlorophenols, parabens, triclosan, which are compounds that effect estrogen signaling by binding to the receptor and have downstream effects (Buttke, Sircar, & Martin, 2012). These compounds are becoming increasingly common in everyday and household use. This type of exposure may be implicated as one of the causes of decreased age of menarche. In a study by Buttke et al, the level of urinary EDCs was analyzed in females between the ages of 6-11 and 12-19 (2012). Females with urinary EDCs above the 75th percentile have significantly lower age of menarche (Buttke, Sircar, & Martin, 2012). These results are worrisome, because pollutants in our environment are influencing the development of adolescents. This is a larger public health concern than previously believed. Further investigations are underway to better understand which products are the most dangerous culprits.

Obesity has become a major epidemic, whereas two-thirds of the Americans are overweight or obese and one-third of children are overweight or obese. While obesity in adulthood can lead to a plethora of health concerns, it was previously thought that childhood obesity might have reversible effects. However, obesity in young females has been shown to have an influence on early-onset puberty. Obesity causes an increase in certain hormonal levels including leptin, insulin, IGF-1, certain binding proteins, and androgens (Marcovecchio & Chiarelli, 2013). Early signs of puberty are not the only effects seen by the hormonal changes associated with obesity, hyperandrogenism may be present as well (Marcovecchio & Chiarelli, 2013). Hyperandrogenism involves increased body and facial hair, alopecia, acne, and increased libido. Both hyperandrogenism and earlier development in females may have extreme social effects in adolescent females.

Nutrition in newborns is predominately breast-feeding at approximately 75%, however, after just one-week postpartum breast feeding incidence drops to 16.2%. Approximately 20% of formula-fed infants are given soy-based formula (Andres, Moore, Linam, Casey, Cleves, & Badger , 2015). Isoflavones are organic compounds that act as phytoestrogens in mammals and are found in soy-based products and may be feared to cause estrogenic effects such as early-onset puberty (Andres, Moore, Linam, Casey, Cleves, & Badger , 2015). Currently, the most recent study on hormonal additives was done in 1988 by the FAO/WHO Committee on Food Additives Joint with the Federal Drug Administration (FDA) which showed no concern for human consumption of hormonal additives (Larrea & Chirinos, 2007). Later, Larrea and Chirinos show that the study may be concerning due to the inadequate scientific elements that were used (Larrea & Chirinos, 2007). Furthermore, previous studies on the effects of hormonal additives on early onset of puberty are inconclusive and current studies are still underway (Andres, Moore, Linam, Casey, Cleves, & Badger , 2015). The conclusions of the current longitudinal studies will be a vital factor in not only post-partum nutrition but child and adolescent nutrition as well.

The significance of all of the theories behind early menarche is due to the psychosocial effects of early maturity of young girls and the unwanted attention they may receive. Early onset of puberty also causes women to have longer exposure to estrogen, which may be associated with several types of cancers, including breast and endometrial cancer. Estrogen exposure also increases risks for cardiovascular disease and high cholesterol. These health-related side effects were significantly lower when women were experiencing menarche at older ages. Clearly, more research needs to be done in order to investigate the multifactorial causes of early menarche in adolescents; however, current studies seem to implicate both environmental and nutritional exposures.

References
Andres, A., Moore, M., Linam, L., Casey, P., Cleves, M., & Badger , T. (2015, March). Compared with feeding infants breast milk or cow-milk formulas, soy formula feeding does not affect subsequent reproductive organ size at 5 years of age. The Journal of Nutrition , .
Buttke, D., Sircar, K., & Martin, C. (2012). Exposure to endocrine-disrupting chemicals and age of menarche in adolescent girls in NHANES. Environmental Health Prospective , 120 (11), 2003-2008.
Larrea, F., & Chirinos, M. (2007). Impact on human health of hormonal additives used in animal production. Rev Invest Clin , 59 (3), 206-211.
Marcovecchio, M., & Chiarelli, F. (2013). Obesity and growth during childhood and puberty. World Review of Nutrition and Dietetics , 106, 135-141.
NIH. (2009-2010). Overweight and Obesity Statistics. Retrieved 2015, from National Institute of Diabetes and Digestive and Kidney Diseases: niddk.nih.gov