Studies explain why girls enter puberty as young as age 7
Girls are more likely now than ever to enter puberty as young as 7, according to a new study released in the journal Pediatrics.
Dr. Frank M. Biro, director of adolescent medicine at Cincinnati Children's Hospital Medical Center and colleagues found 15 percent of Latina girls, more than 10 percent of white girls, and 25 percent of black girls were beginning puberty at age 7.
This is what the researchers found after they analyzed data from 1238 girls ages 6 to 8 who live in Cincinnati, East Harlem N.Y. and San Francisco.
The researchers also found by age 8, 10 percent of whites, 43 percent of Blacks and 31 percent of Latinas had entered puberty.
Early puberty can lead to medical problems like low self-esteem, eating disorders, depression, early sexual activity, later menopause, elevated risk of breast cancer.
Diet and environmental pollution are believed to cause early puberty in girls. Earlier this week Food Consumer reported studies that suggest that poor diet quality and high levels of hormone IGF-1 are associated with early puberty.
Below are summaries of some more studies that may give readers some idea about how girls enter puberty at such early ages.
Phthalate exposure linked to early puberty in girls
One study led by Chou Y.Y and colleagues at the National Cheng King University Medical College and Hospital in Tainan, Taiwan suggests that exposure to phthalate may get girls in puberty early.
The study published in the Journal of Pediatric Endocrinology & Metabolism was meant to determine the levels of phthalate ester metabolites in girls who had puberty earlier and their association with environmental factors like phthalate.
Phthalates, which are endocrine disruptors, are a group of chemicals used mainly as plasticizers to soften polyvinyl chloride. In the United States, Canada, and Europe, these chemicals are being phased out due to concerns over their safety.
For the study, Chou et al. compared metabolites in urine samples from 30 girls who exerpeinced early puberty including 30 girls with premature thelarche and 26 with central precocious puberty with that in urine samples from 33 normal controls.
The researchers found girls who entered puberty early had an average of 96.5 ng/ml of monomethyl phthalate compared to 26.4 ng/ml in girls who did not.
Some types of phthalate were associated with intake of seafood, meat, drink and the use of plastic cups and plastic handi-wrap.
Childhood obesity linked to early puberty in girls
Researchers at the University of Michigan C.S. Mott Children's Hospital reported in the March 2007 issue of the journal Pediatrics that childhood obesity may be one reason for early puberty in girls.
Joyce Lee MD and colleagues found a higher body mass index score in girls as young as age 3 and large increases in BMI between age 3 and first grade were associated with early puberty defined as having breast development by age 9.
Another study in the December 2009 issue of PLoS One also found the emerging obesity epidemic was linked to the timing of puberty.
Aksglaede L and colleagues from University of Copenhagen in Copenhagen, Denmark found the heavier girls were at age 7, the earlier they entered puberty.
The study was based on data from 156,835 children who were born between 1930 and 1969 and attended primary school in the Copenhagen municipality.
BMI was significantly inversely associated with the age for onset of pubertal growth spurt and peak height velocity, the stuyd found.
Obesity is blamed for everything, a health observer commented. He said obesity is merely a symptom and the real risk is what causes obesity and these studies suggest that a girl's diet is important in determining her puberty status.
Animal protein pushes girls to enter puberty earlier
One recent study led by Günther A.L. and colleagues from Fulda University of Applied Sciences in Germany confirmed that diet plays a critical role in the timing of girls' puberty.
Günther reported in the March 2010 issue of Journal of Nutrition that those who had highest total intake of animal protein at age 5 to 6 experienced the pubertal growth spurt, peak height velocity (APHV), and menarche in girls about 0.6 years earlier than those with lowest intake.
On the other hand, high intakes of plant protein at 3 to 4 and 5 to 6 were related to later ATO, APHV, and menarche/voice break.
The researchers concluded that "These results suggest that animal and vegetable protein intake in mid-childhood might be differentially related to pubertal timing."
By David Liu
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