By now, most people who pay attention to such things know that American girls, on average, are getting their periods and their breasts earlier than their ancestors. The question of why this is happening, however, is a bit trickier. For anyone truly curious, Sandra Steingraber has written a report, published by the Breast Cancer Society, called "The Falling Age of Puberty in U.S. Girls: What We Know, What We Need to Know."
Grist just put up an excerpt of it, and unfortunately for anyone looking for an easy answer to the question, Steingraber says that there isn't one. However, she does do a good job of pulling together a summary of what we do and don't know. Some salient points:
-- On average, American girls today get their periods a few months earlier than girls did 40 years ago. They get their breasts one to two years earlier.
-- Everyone acknowledges the changes, but no one's sure of the exact cause. Potential factors? Everything from obesity to television viewing, sedentariness, family dysfunction, preterm birth, formula feeding and chemical exposure. (This is made even more confusing by the fact that several of these factors themselves are related.) One thing Steingraber says is certain, though, is that these variables are present more often in poor communities, and that African-American children are most likely to be exposed to them. Perhaps uncoincidentally, African-American girls also reach puberty, on average, faster than any other group.
But who really cares when you get boobs? Well, turns out that hitting puberty earlier is associated not only with a higher risk of breast cancer but with "high-risk" behaviors like smoking, drinking, drugs, crime and unprotected sex -- and higher rates of depression and anxiety.
OK. But couldn't this all have something to do with the fact that girls today are better nourished? Maybe girls are menstruating earlier because their bodies are ready for it. Unfortunately, Steingraber doesn't think so. She points out that this may have been true from the mid-19th to the mid-20th centuries, but that in the past 50 years, "additional forces have been at work."
The description of what those additional forces might be is enough to make parents want to lock their girls in protective bubbles until they hit 13. Possible factors include endocrine-disrupting chemicals like those found in estrogen and testosterone creams (that one's unsurprising) and in some ointments, hair tonics and ingested pharmaceuticals. But it doesn't stop there. Steingraber mentions that endocrine-disrupting chemicals can also be found in things like pesticides, packaging and building materials. In other words, before you imprison your daughter in a bubble, you might want to check what it's made of.
As if that's not enough, this accelerated puberty may also be affected by the hormones that are given to cattle (and then passed on to us through meat and dairy products), exposure to lead (which delays menarche) and cigarette smoking (which speeds it up). So, uh, be careful when you paint the bubble and ... raise your daughter vegan?
Steingraber has a few more practical suggestions: We should be encouraging mothers to breast-feed, educating the public more about what endocrine-disrupting chemicals are (and where they're found), eating organic when possible, and supporting efforts in school districts to encourage exercise and healthy eating habits. (She suggests a few more things, too -- check them out yourself if you don't like my bubble idea.) It's unfortunate that in her research, Steingraber didn't discover a magical cure for the problem -- but if you're looking for a good review of what we do know (and what issues still need investigation), check out her article.