Parents often tell their children not to grow up so fast, but the kids aren’t listening.
A 2010 study found that girls as young as seven are showing signs of puberty, and now we know boys are starting puberty earlier than ever. On Saturday, the journal Pediatrics published the results of a sweeping study of the sexual maturation of 4,131 boys in 144 doctor’s offices across the nation. The study reported the median age of puberty for African-American boys was nine, while the median for Hispanics and Caucasians was 10 years old. (That's up to two years earlier than previously reported) A 2010 study of 1,239 girls found that 15 percent showed the beginnings of breast development at age seven.
Perhaps most startling are the suggested causes: added hormones in food such as milk and meat, higher levels of obesity, higher density of calories in processed foods, physical inactivity, and chemicals in food and water. (No study to date has proved conclusively that any of hormones in food cause either premature or delayed puberty.)
Perhaps the strongest case that childhood nutrition affects puberty is an apparent connection between early puberty and body mass—especially in girls. Obesity has tripled in the last 30 years among children, increasing from 6.5 percent in 1975-80 to 19.6 percent in 2008. Suspecting there was a connection between heavier kids and earlier puberty, Dr. Paul Kaplowitz, a researcher in the Department of Endocrinology at Children’s National Medical Center, Washington, D.C., examined in 2008 a number of studies to that point and was able to draw a fairly strong correlation between obesity and earlier puberty in girls. The 2010 study supported Kaplowitz’s conclusions, finding that heavier girls with a higher body-mass index were more likely than others to begin puberty early.
Dr. Louise C. Greenspan, a practicing pediatric endocrinologist at Kaiser Permanente San Francisco and one of the researchers on the ongoing girls’ puberty study, says she takes the “precautionary principal” in advising parents on things they can do to address early puberty: If you don’t know that something is harmful, then you assume that it is before you prove it is safe. She champions healthier eating, advising parents to use the Environmental Working Group’s “Dirty Dozen” guide when buying produce. And while it hasn’t been proven that added hormones in food, like milk, are a cause of onset puberty, she says “it’s better for cows and better for the environment—if not better for kids.”
“If we needed one more reason to change our behaviors, this works,” she adds.
Food and nutritional disparity among people of color may explain why African-American and Hispanic girls were much more likely to show early signs of puberty than white girls. Black girls are obese at a rate (29.2 percent) almost twice that of white (14.5 percent) and Hispanic (17.4 percent) girls.
While the Pediatrics study of boys concluded that the causes of early-onset puberty in boys needs further study, Greenspan believes that external changes in the world—which include a gradually deteriorating diet over the last century—certainly affect the timing of puberty in all children. Regardless of the specific causes, increasing the health of all children—especially those who are in at-risk communities—is imperative.
“What can we do in those communities to help them be more healthy?” Greenspan asks. “What’s happening on a bigger scale that’s causing obesity, that’s related to these other problems?”
Steve’s story about healthy fast food was anthologized in Best Food Writing 2011. His food and general interest stories regularly appear in Edible Boston, Boston Magazine, The Boston Globe, and other places. Email Steve | @thebostonwriter