Saturday, February 7, 2015

The increasing incidence of early-onset puberty

“Going through puberty as a young girl is so confusing. This monster invades your body, changes things and makes things grow, and no one tells you what's going on.” — Katharine Isabelle, Canadian actress

THE AVERAGE age of the onset of puberty in girls in the United States has been getting younger and younger, and there's been much speculation as to the cause. I found this New York Times article about a 10-year study tracking 1200 girls intriguing because it reveals surprising correlations. 

What Causes Girls to Enter Puberty Early?
By Louise Greenspan and Julianna Deardorff
February 5, 2015

Record numbers of girls not yet old enough for middle school are starting puberty. Almost by definition, puberty arrives at an awkward age, but these are grade-school girls, thrown into a developmental gantlet before they are ready for the change.

As mothers of young girls, we see this phenomenon and fret over the implications. Early puberty can lead to eating disorders, depression, substance abuse, early sexual activity and, later in life, breast cancer. But as doctors, we wince at misleading stories that blame substances that are not likely to bear the primary responsibility — hormones in our meat or soy in our diets, for instance. The real culprits include two problems that are often overlooked: obesity and family stress.

Chemical exposures may also disrupt girls’ puberty, but less is known in this area. To better understand the early puberty phenomenon, we, together with colleagues, are conducting a continuing study of more than 1,200 girls tracked since 2005. Puberty used to begin at age 10 or 11. In our study, we found that by the age of 7, 23 percent of black girls, 15 percent of Hispanic girls and 10 percent of white girls had started to develop breasts. It is clear from the data that overweight girls are more susceptible to early puberty. Body fat secretes estrogen, a hormone that is normally released from the ovaries during puberty and is responsible for breast development. Excess body fat serves as an additional source of estrogen, and the result is earlier breasts.

Sugary drinks contribute to today’s kids’ being more overweight than in previous generations. In fact, according to one study, at least 20 percent of the weight gained by the population from 1977 to 2007 can be attributed to sweetened beverages. The role of sweeteners is intriguing. New research announced last week by the Harvard School of Public Health suggested that girls who drank more sodas were also more likely to reach puberty early, regardless of whether they were overweight.

More surprising, strong evidence reveals that emotional stress in a girl’s family can jump-start puberty earlier. Growing up in unpredictable households with high levels of conflict leads to early maturation. So does early sexual abuse. A girl who grows up without her biological father is twice as likely to get her period before age 12 compared with a girl reared with her father in the home. The effects of fathers may or may not be linked to stress, but a father’s presence in the home does seem to matter when it comes to puberty.

Endocrine-disrupting chemicals are also a concern because they can mimic hormones, like estrogen, that are the key players in a girl’s body during puberty. Many chemicals, including those in fire retardants and plastics, disrupt reproductive development in animals; however, more research is needed on humans. And research hasn’t identified a single smoking gun.

While each individual chemical may not have a direct effect on puberty, we have no idea how the hundreds of chemicals that a girl is exposed to daily might cause multiplicative effects in her growing body. It may be a combination of exposures that do real damage, as well as the developmental timing of those exposures. And going “all natural” may not be the solution because some naturally occurring substances — for example, lavender and tea tree oils — are pervasive in personal care products and might act as estrogens in the body.

So what’s a parent, and society at large, to do?

There are ways to protect against early puberty. Breast-feeding early in life appears to help. What’s more, when a mother maintains a healthy weight before and during pregnancy, her daughter is less likely to get her period early. Work by our team also shows that consuming soy foods may delay puberty, which is contrary to the widely held belief that all soy-based products accelerate it. Providing a warm emotional environment at home can not only help prevent early puberty, but also mitigate the psychological effects if it occurs. To buffer against toxic stress, parents should prioritize setting aside time to engage with their daughters and bond emotionally.

We also need to continue to improve our daily menus and enhance the quality of school lunch programs. Opting for alternatives to sweet drinks and candy as the ubiquitous rewards for school achievement, good behavior and celebrations is a start. And adults need to demonstrate healthy habits that support our own ideal weights and reduce stress levels.

Puberty is a complex biological phenomenon that is unlikely to be triggered by a single factor. Rather than be overwhelmed by the multitude of targets to tackle, perhaps we can begin with a focus on obesity and stress, the two culprits that research shows have direct and detrimental effects. It also makes sense to take a cautious approach toward chemicals in our households and in our foods. As mothers and researchers, we advocate for more research and also support the precautionary principle when it comes to making policy: If we don’t know whether something is safe, then we shouldn’t be exposing our children to it.

2 comments:

  1. Wow, that IS contrary to much of what I thought was true. But all those things are what parents try to protect children from, so that makes sense Good piece - thank you.

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  2. Hi Liz,

    My apologies if I am replying twice to your comments. I get a notice in my email whenever someone comments on a Hey Look post, and I reply, but I don't know if they actually go through or not because when the email comes in, it says "no reply." So then I think that maybe the way I'm supposed to reply is directly on the blog. So . . . if I'm double sending, sorry! Could you let me know if I am?

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