Does your 8-year-old daughter need a training bra? If so, you’re not alone. Studies have established that girls today are entering puberty earlier than their counterparts several decades ago.
The beginning of menstruation, or menarche, starts six months earlier on average than 40 years ago, but breast development is starting two years earlier. The clock has also moved up for other early pubertal signs, including body odor and the growth of pubic hair.
It is a trend that demands attention, and the authors of The New Puberty aim to help by providing parents with practical tools to navigate their way through this important stage of their daughters’ lives.
The authors are Julianna Deardorff, a UC Berkeley associate professor of maternal and child health in the School of Public Health and a licensed clinical psychologist, and Dr. Louise Greenspan, a pediatric endocrinologist at Kaiser Permanente and UCSF associate clinical professor. The book not only draws upon their collective experience in both pioneering research and clinical practice, but it synthesizes the body of literature in this field.
They outline the key factors at work in speeding up the rate of girls’ development, and they also bust some common myths about puberty prompters.
Deardorff sat down with the NewsCenter to discuss the key messages for parents from The New Puberty. The interview has been edited for length and clarity.
NewsCenter: What do we mean when we say “early puberty”?
Deardorff: One of the things that inspired us to write this book is that people don’t understand what puberty is. It’s not a single event. Many people think that onset of puberty is marked by a girl’s first period. What we know is that hormonal changes have started years prior to that. Puberty is a series of events that unfolds over many years. Breast development is typically one of the first visible signs of puberty starting, but even that is preceded by vast hormonal changes.
In large part, this book became a reality because Louise and I were working together for the past 10 years, and in the course of our work it became evident that girls were entering puberty earlier. This was confirmed both in the research that we were conducting and in findings by an expert panel published in the journal Pediatrics.
How early is early?
Louise is an endocrinologist, and in the past, when she was first trained in her profession, any girl showing signs of puberty before age 8 would cause concern and warrant a fairly extensive workup by a pediatric endocrinologist. But using recent data from our longitudinal study of over 1,200 girls, we found that at age 7, a significant number of girls were showing signs of early breast development. So this confirmed past studies and started to ring the alarm bells.
What makes this so alarming?
What really worried us was that we started to hear the term “the new normal” to describe what was happening with girls’ puberty. Louise and I were wondering, are we just going to accept this trend as normal? Is that wise given all of the documented deleterious outcomes that are linked to girls’ early puberty? In the short term, early-maturing girls are at higher risk for depression, anxiety, eating disorders and early initiation of substance use and sexual behaviors. In the long term, early menstruation has been linked to breast cancer risk in adulthood. Research has also shown increased cardiovascular disease risk as well as all-cause mortality and risk for other reproductive cancers.
These health outcomes made us question whether we should accept this shift in pubertal timing as “normal.”
Do researchers know why this is happening?
Our book takes scientific literature from a number of different fields and, for the first time, synthesizes the research findings in one place. What we find are three main culprits at work. The first is obesity and overweight, which likely accounts for much of the secular trend toward earlier development. The second is environmental exposures, particularly chemicals that mimic hormones in a girl’s body. And the third is stress in the girl’s environment.
Obesity seems to be responsible for the largest proportion of the variance in timing of girls’ puberty. Body fat secretes estrogen in the body, so when there’s a higher accumulation of body fat, there is more estrogen secreted. We believe that those higher estrogen levels are influencing breast development.
The chemical exposure research, as it relates to puberty, is really in its infancy in humans. There is strong evidence that certain chemicals disrupt the pubertal process in animal models, causing either early or late development. What is unclear is how these endocrine mimickers affect developing girls, at what dosages, and during which time points.
What kind of chemicals are we talking about?
There’s evidence that pesticides and flame retardants mimic hormones in our bodies and act as endocrine disruptors. Other suspects are chemicals called plasticizers, like in the lining of cans and food containers. BPA [Bisphenol A] has been suspected, but research in humans has not borne out the relationship with early puberty. There has been some interesting recent work examining various chemicals in personal care products, such as cosmetics and body lotions.
While we have suspicions, we don’t have the evidence right now to call any particular chemical out. It’s especially tricky when you consider the potential interactive and additive effects of these chemicals, and how those chemicals interact with other factors – like genes, body fat and stress – to potentially have more potent effects.
It’s also important to remember that natural is not always safe. There are some case studies buried in the medical literature showing that lavender and tea tree oil – specifically the combination of those two ingredients – can act as powerful estrogen mimickers. They have been linked to signs of puberty in very young children. This is notable because those ingredients can be found in a lot of personal care products for children.
I’ve heard concerns over plant-based estrogens in foods like soy. Should we be careful about soy in our diet?
That’s a huge potential myth that we begin to bust in the book. It’s much more nuanced than is conveyed in the popular media. Our preliminary work has shown that plant-based soy products might actually be protective against early puberty. The timing of exposure is probably really important, though. We believe that early exposure to plant-based soy, not soy additives, may create some estrogen resistance in young girls and delay puberty. Right now, however, we don’t know if soy consumption is a marker of a better diet, or if there is something particular about phytoestrogen exposure that delays puberty. We also know a high-fiber diet is correlated with later puberty, as well, which could also be an indicator of a good diet.
One of the questions we get a lot concerns soy-based formulas. We really don’t know. Generally, we believe that the protective effects of soy may be from plant-based foods, not the derived versions of soy that have ended up in our diet in different ways. We still believe that, when possible, breast milk is best.
Are there any concerns about hormones in foods like milk and meat?
That’s another myth busted in our book. There’s evidence out there that hormones in milk and meat products are metabolized in the intestines and likely aren’t potent enough to push early puberty.
But one of the things we’re really concerned about is the potential endocrine-disrupting properties of antibiotics in our food. Using antibiotics in medical settings is one thing, but adding antibiotics to our food, in the raising of livestock, has pediatric endocrinologists concerned. Antibiotics are given to animals to help fatten them up and this causes them to enter puberty early. This, of course, results in higher meat and milk production. This issue is on our radar and certainly in need of investigation.
Okay, let’s move on to stress as the third factor influencing early puberty.
We know from the scientific literature that the effects of stress on puberty have been consistent and compelling. During intense times of war, menarche is delayed at a population level. But what has been confirmed more recently is that moderate, chronic levels of stress appear to have an accelerating influence on girls’ puberty.
Growing up in homes that are inconsistent, unpredictable, high in conflict, low in warmth, low in emotional connectedness, is associated with girls’ bodies entering puberty earlier.
One of the dominant theories to explain this is that the body is very sensitive during the early years to its social environment. Early maturation in unsafe circumstances is an evolutionary strategy. If you’re growing up in an environment that is not perceived as safe and consistent, then it makes a lot of sense to achieve reproductive readiness faster. In addition, there may be biological pathways leading from stress and stress hormones to early puberty, and this is something we are examining in our ongoing studies.
Your book brings out the racial differences in early puberty. Can you explain that?
Earlier I mentioned that in our study of over 1,200 girls, we found that at age 7, many showed signs of early puberty. We found that far more ethnic minority girls were affected. Among African Americans, 23 percent showed breast development at age 7. In comparison, we found breast development in 15 percent of Latina girls and 10 percent of non-Latina white girls.
Generally this has just been assumed to be a “race effect,” and people haven’t paid a huge amount of attention to why these disparities exist. What’s emerging from the most recent research, and also an important reason we wrote this book, is that there are many things in the environment that are pushing puberty to start earlier, and ethnic minority youth are disproportionately exposed to those factors. We’re talking about chemical exposures, we’re talking about obesity and we’re talking about stress, all of which are more prevalent in communities of color and impoverished communities in the U.S.
So what can we as individuals do?
Some of the risks associated with early puberty are modifiable, and we go over those in the book. Let’s start with the low-hanging fruit. Have your children drink water, not sweetened beverages, and switch from plastic bottles to glass or stainless steel. If you can just do that, that could result in a huge shift at the population level.
To reduce other environmental exposures, use perfume-free products and, if possible, try to buy local and organic produce and flowers. For pesticides, a primary issue from my standpoint is to support organic farms. People who are working in conventional fields are exposed to high levels of pesticides, and often live and raise their children near fields that are consistently sprayed. In agricultural communities, kids are going to school or playing near pesticide-sprayed fields. That’s a great reason to support organic farms. The amount of exposure these farmworker families are getting is so much higher than what we’re getting from individual pieces of fruit.
In terms of stress, it’s important to create an environment that is safe and nurturing, both to try to prevent the effects of stress on early puberty and to provide a foundation for support once a girl starts puberty. If you have an early developer, it’s key to provide a strong family foundation and open the lines of communication to discuss the changes that her body is going through.
I think when some parents or adults hear the word “puberty,” they leap to sex immediately. But there are so many signs of puberty that come long before any thoughts of sex begin, particularly when you’re talking about a girl at age 7 or 8. Usually one of the first signs of puberty is body odor, so parents can talk about hygiene and the best way to the wash under your arms. Those conversations don’t need to be intimidating or awkward. And they lay the foundation for safe conversations as a girl’s development continues.
We have a lot of practical tips in our book about deodorant, bralettes, tank tops and sanitary products. Our goal was to help parents understand the nitty-gritty of the things that they’re going to be thinking about at different stages of their daughters’ development.
We also walk through what’s happening during puberty in a girl’s body, and what’s happening in terms of brain development. This may help parents have a better perspective on why girls do the things they do from a neuro-maturational perspective. We try to dispel a lot of myths about raging hormones and out-of-control youth to arm parents with some important facts. We also include a questionnaire to help parents determine whether their daughters are going through puberty early and whether they should see their doctor.
If you’re concerned, and you go to a doctor, it helps to go armed with knowledge so you can maximize your time with the pediatrician. You want to know what questions to ask. And you should know when you need to be referred to a specialist. Our goal was to provide guidance to parents to help navigate the medical world and also their daughters’ puberty, whether it happens early or on time.