By Lisa M. Belisle, MD, MPH
Originally published March 2007, Parent & Family
As any parent can tell you, most children grow up before we are fully ready. One minute we are answering newborn cries for a midnight (then two o’clock, four o’clock and six o’clock) snack; the next we are fielding adolescent ride requests. It seems the gap between preschool and puberty is ever shrinking. In fact, some studies suggest that this idea is not simply a product of our wistful adult minds. Children — specifically girls — may actually be reaching adolescence more rapidly. There are several theories as to why this may be so.
The onset of puberty is largely a result of genetics. Most girls experience breast development and the onset of their first period (also called menarche) at about the same time their mothers did. There are some differences between races: African-American females tend to be younger than their Asian and non-Hispanic white counterparts. According to the National Health & Nutrition Examination Survey average, girls now experience menarche at age 12.34—almost six months earlier than girls in the 1960s.
An earlier age at menarche has several drawbacks. Puberty, of course, is a source of significant emotional upheaval—made worse when it takes place in younger years. In addition, premature puberty can lead to obesity in adulthood. It also makes women more susceptible to breast cancer later in life.
Puberty is a result of the impact of hormones on reproductive and other tissues. In girls, the primary hormone is estrogen; in boys, testosterone (though both genders have smaller amounts of the other hormones). For the most part, estrogen is produced by the ovaries. Recent research, however, has shown that fat cells also manufacture estrogen under the influence of the hormone leptin. Heavier children are thus more likely to go through puberty sooner.
Early puberty has also been attributed to childhood exposure to non-human hormone-like substances. These have been labeled “Xenoestrogens.” Xenoestrogens are known to mimic the effects of estrogen, causing changes in breast, ovarian and uterine cells.
Xenoestrogens come from both natural and man-made sources. Natural sources include soy and red clover. Man-made sources include an array of common chemicals. Some of these have been in use for many years. Others are no longer used, but can still be found in the environment—in the air, in the water, and in the food we eat.
Xenoestrogens are part of a larger class of compounds thought to have a potentially negative effect on the reproductive system. These have been called endocrine or hormone disruptors. Hormone disruptors have been blamed not only for early puberty, but for infertility and cancer, as well. Examples of these are:
- Plasticizers, which are used to make plastics strong and flexible. These are known to leach from plastic wrap and storage containers into food and water. Certain plasticizers—the most well known being phlalates—have even been used in infant pacifiers and toys. Phlalates have actually been banned in Canada.
- Surfactants, which allow paint, pesticides and detergents stick to their target surfaces, and
- Perchloroethylene (also known as PERC), which is used in the dry cleaning industry.
In small amounts, xenoestrogens and other hormone disruptors are not likely to be harmful. Unfortunately, many of these are stored in the body—usually in the fatty tissues and the liver. They are also passed to infants via the placenta before birth, and through the breast milk during breastfeeding. The buildup of these stored substances over time is called the ‘body burden.’
While we may have little control over when our kids reach adolescence, we can minimize their body burden, and their chances of early puberty, by:
- Eating lower fat diets and limiting animal products to those raised organically. (Notice that the idea is ‘lower’ fat. Babies and children do need some fat in their diets for brain development.)
- Eating organic foods in their original form—choosing those with less packaging, which will mean less exposure to plasticizers (and preservatives).
- Knowing where our water is from—public water is tested regularly for harmful substances. Well water should be, as it is also susceptible to ground contaminants such as pesticides.
- Selecting safe household cleaning and decorating products.
- Finding alternative ways of dealing with unwanted insects and weeds—being very careful to use the minimum amount of pesticides and herbicides, and limiting human and animal exposure.
- Using care with clothes recently retrieved from the dry cleaners—airing them outside when possible.
- Educating ourselves. One interesting read is Sandra Steingraber’s book, Living Downstream (Vintage, 1998). For more information see Resources below.
It is important not to go overboard as we seek to limit our children’s exposure to hormone disruptors and other chemicals. Many people succumb to fear when they first learn of these, or feel completely overwhelmed. Knowledge is power, but a balanced approach is best. As with anything, we must weight the risks and benefits of our actions. We must enjoy our children’s growing years. They are behind us all too soon.
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RESOURCES:
MaineHealth Learning Resource Centers, Falmouth 207-781-1730, Scarborough 207-885-8570
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