By Martha Rosenberg

Sixteen percent of U.S. girls are now experiencing breast development by the age of 7 and 30 percent by the age of 8. Girls in poorer countries spared this trend—until they move to developed countries. Clearly something is affecting the hormones of U.S. girls.

Scientists don’t dispute early puberty is on the rise but they do not agree on the reasons. Is it bad diets and lack of exercise which cause growing obesity? Is it soft drinks themselves, even when not linked to obesity? Is it the common chemicals known as “endocrine disrupters” which exert estrogen-like effects (and also cause obesity)? Is it the many legal, unlabeled hormones used in U.S. to fatten livestock?

How much weight a girl gains affects early puberty because “when the body senses it has extra calories, enough to sustain a pregnancy, the fat tissues release a signal into the bloodstream,” reports KATU 2 News. “That signal then travels to the brain, telling it that sexual development is a 'go.' Doctors see the opposite happen in girls who suffer from anorexia. When the body is starved of calories, the first thing it does is shut down sex hormones.”

There are many reasons why precocious puberty is undesirable. “Girls with earlier maturation are at risk for lower self-esteem and higher rates of depression. They are more likely to be influenced by older peers and more deviant peers, and initiate intercourse, substance use, and other norm-breaking behaviors at younger ages,” writes Frank M. Biro, MD, in the journal Pediatrics. “The biologic impact of earlier maturation includes greater risk of several cancers, including breast, ovarian, and endometrial cancer, as well as obesity, hyperinsulinemia, and hypertension.” Heart disease risk is also increased.

Finally, precocious puberty means girls will not grow as tall. “The early occurrence of puberty shortens the duration of pre-pubertal growth in a fashion that is not compensated for by an increase in peak amplitude,” says a paper in the Oxford journal. In historical studies, “there was a negative correlation between the age of onset of precocious puberty and adult height, confirming the poor height prognosis of the most severe and early cases.”

Meat May be a Factor

A 2010 study in Public Health Nutrition of 3,000 girls found that girls who ate eight portions of meat a week by age three, and 12 portions of meat a week by age seven were likely to have an early start of menstruation. In fact, the girls were 75 percent more likely to have begun their periods by the age of 12 if they were eating a high-meat diet when they were seven years old. Not mentioned in the study, led by Dr. Imogen Rogers from the University of Brighton, was whether the meat had been grown with livestock hormones, a practice which also raise questions.

“We have always had access to junk food, but never in human history have we been the subjects of such an intense ingestion of chemicals and hormones,” writes Christina Pirello, writing on the Huffington Post. “Dr. Andrew Weil states that more than two-thirds of the cattle raised in the U.S. are given hormones, usually testosterone and estrogen to boost growth. According to Cornell, there are actually six hormones commonly used in meat and dairy production: estradiol and progesterone (natural female sex hormones); testosterone (natural male sex hormone); zeranol, trenbolone acetate and melengesterol (synthetic growth promoters that make animals grow faster).” Pirello urges people to eat more produce and avoid hormone fed meat, noting, “If hormones can make an animal fat, what do you think will happen to us?”

Endocrine disrupters, chemicals in toxins everyday products like hand soap, shampoos, cosmetics, cleaning products and plastics that mimic estrogen may also be a factor. They are even found in carpets, couches, food containers and thermal receipts. Though tea tree oil and lavender are thought to be “natural,” they have also been linked to precocious puberty.

While there are drug treatments doctors can give to girls exhibiting precocious puberty that will block the effects of the soaring hormones, prevention is clearly preferable. Certainly a “green household,” with as few endocrine disrupting chemical products as possible is a good start as is a “green diet” without excess chemicals, hormones and of course calories.