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IC professor writes about cancer's link to early puberty

By Linda Stout | Journal staff

TRUMANSBURG — American girls are going through puberty younger and younger, putting them at higher risk for breast cancer along with learning problems and mental health issues.

“We know that if you get your first period before the age of 12, your risk of breast cancer is 50 percent higher than someone who gets their period at 16,” said Sandra Steingraber, an award-winning environmental author who teaches at Ithaca College. She formerly worked for the Sprecher Institute for Comparative Cancer Research Program on Breast Cancer and Environmental Risk Factors at Cornell University.

The Breast Cancer Fund published her monograph, “The Falling Age of Puberty in U.S. Girls: What We Know, What We Need to Know,” this month. Her new work builds on discoveries that began after she was diagnosed with cancer when she was in college. She documented her experiences with cancer in her book, “Living Downstream: An Ecologist Looks at Cancer and the Environment” (1997). She also wrote “Having Faith: An Ecologist's Journey to Motherhood” (2001), which explored fetal toxicology and genetics with respect to her own pregnancy.

What she found in studying puberty was that white girls' periods start at 12.6 years; for black girls, it's even earlier, at 12.1. That's a few months earlier than their mothers or grandmothers 40 years ago, Steingraber reports.

“Early puberty is not only a women's issue, but it is a class and race issue as well,” Steingraber said.

Girls' breast development starts one or two years earlier than getting their periods. Half of all U.S. girls show signs of breast development by their 10th birthday, 14 percent growing breast buds between age 8 and 9.

Since the monograph came out and during Breast Cancer Awareness Month, the media attention and speaking engagements have kept Steingraber, a Trumansburg resident, busy.

“I've been riding the tiger of a lot of media attention on it,” said Steingraber. She appeared on “Good Morning America” a few weeks ago and had speaking engagements last week in Olympia and Seattle, Wash.

Steingraber wasn't entirely surprised to document that puberty starts earlier. She'd been hearing stories, sometimes in whispers from parents and had questions from family doctors about early puberty. For instance, there was a 5-year-old girl who already had pubic hair. And she regularly heard of third graders getting their periods. Her research was able to back that up and pose hypotheses as to why.

The very first signs of puberty, pubic hair, appear at about age 9 for black girls and 10 for white girls, she found.

“The childhoods of U.S. girls have been significantly shortened,” she wrote.

In contrast, while she was exhaustively researching the monograph, she was reading chapters of Louisa May Alcott's 1868 novel “Little Women” as a bedtime story to her daughter. The age of puberty, according to European records, was higher back then.

She quotes the character Jo, age 15, saying to Meg, who's 16, “Don't try to make me grow up before my time, Meg. It's hard enough to have you change all of the sudden; let me be a little girl as long as I can.”

“It really struck me. (Meg is) developing breasts and dressing in more provocative ways,” she said.

There are numerous social and psychological risks of early puberty, like earlier use of drugs, alcohol and sexual experiences, she found.

“We've basically chopped six years out of the childhood of our girls, and you learn better before puberty. I think there are huge implications here,” she said.

After puberty, the brain is less plastic, less able to learn new languages or an instrument, she said.

“Our bodies are an environment,” Steingraber said.

In “The Falling Age of Puberty in U.S. Girls: What We Know, What We Need to Know,” she writes that early breast development — which is sometimes, but not always, coupled with early periods — seems to influence breast cancer risk in and of itself.

What comes first, pubic hair or breasts, is also a factor.

“The tempo of puberty may also affect later breast cancer risk: A long period between breast budding and first ovulation creates a wide ‘estrogen window' that is thought to be favorable to the future development of breast cancer,” she writes, citing a 2004 study.

In addition, “Girls who enter puberty with breast budding as the presenting event may be more likely to develop breast cancer in later life than girls whose puberties manifest with pubic hair,” she writes, citing a 2003 study.

Causes

The reasons for early puberty are not completely clear, but Steingraber said she gleaned a variety of reasons related to, as she calls it, “living an American lifestyle,” from dietary fat, toxins in the environment and obesity.

Steingraber's monograph draws on epidemiology, endocrinology, toxicology, evolutionary biology, sociology, child development, nutrition, veterinary medicine, media studies and anthropology.

She explains the problem as ecological, like chemicals in food and the environment that disrupt hormones.

“Certain plastics and pesticides can signal early puberty. We also know that young girls have these chemicals in their system because we can test them in their urine,” she said, noting that animal evidence suggests this, too.

Various aspects of obesity — obesity itself and hyperinsulism (insulin resistance) — appear to be factors.

“The role of obesity is strong. It's almost certainly playing a role in the story. It's not the only factor. Lean girls are going through puberty earlier, and even among lean black girls, black girls are going into puberty sooner,” she said, suspecting that early puberty is affected by some kind of endocrine disruptors.

Farmers know that heifers, young female cattle, enter puberty earlier by being weaned, confined and put on a high-calorie diet.

It's similar with young human females, with early weaning, too sedentary a lifestyle and junk food.

For example, formula feeding has been linked to early puberty, she said.

She considers other environmental exposure factors in early puberty, including high and low-level exposure to endocrine-disrupting chemicals like cosmetics containing estrogen or testosterone or to polybrominated biphenyls, or PBBs, used as flame retardants.

She also looks at hormones in meat and milk and at how tobacco smoke accelerates puberty.