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Link Between BPA And Childhood Obesity Is Unclear

Sep 18, 2012
Originally published on September 18, 2012 8:23 pm

BPA could be making kids fat. Or not.

That's the unsatisfying takeaway from the latest study on bisphenol A — the plastic additive that environmental groups have blamed for everything from ADHD to prostate disease.

Unfortunately, the science behind those allegations isn't so clear. And the new study on obesity in children and teens is no exception.

Researchers from New York University looked at BPA levels in the urine of more than 2,800 people aged 6 through 19. The team wanted to know whether those with relatively high levels of BPA were more likely to be obese.

But the results, published today in the Journal of the American Medical Association, didn't offer a simple answer to that question.

Among white kids and teens, higher BPA levels were associated with more than twice the risk of obesity. With black and Hispanic youth, though, BPA levels didn't make a difference.

"When we find an association like this, it can often raise more questions than it answers," says the study's lead author, Leonardo Trasande, an associate professor of pediatrics at New York University. There's no obvious reason why one group of kids would be affected by BPA while another group wouldn't, he says.

Also, there's no way in this study to know whether BPA is actually causing kids to put on weight, says Frederica Perera, who directs the Columbia Center for Children's Environmental Health. "Obese children may be simply eating and drinking foods that have higher BPA levels," she says.

And even if BPA is playing a role in weight gain, it may be just one of many chemicals involved, Perera says.

"Our center has recently published a study showing that exposure to another group of endocrine disruptors, polycyclic aromatic hydrocarbons or PAH, was associated with obesity in the children," Perera says. Those hydrocarbons are typically a part of air pollution in cities.

Some of the uncertainty about BPA may come because the researchers had no way of knowing how much exposure kids in the study may have had in the womb — the time many scientists believe chemical exposure is most likely to have a lifelong effect.

"Clearly we need a longer term study that examines exposure in the earliest parts of life," Trasande says. Even so, he says, it may be time to rethink childhood obesity.

"Diet and physical activity are still the leading factors driving the obesity epidemic in the United States," Trasande says. "Yet this study suggests that we need to also consider a third key component to the epidemic: environmental factors that may also contribute."

The study clearly does not answer the question many parents have, says Mike Dedekian, who runs the pediatric obesity clinic at the Barbara Bush Children's Hospital in Portland, Maine.

"Does BPA cause obesity? We don't know yet," he says. "Does this study raise our level of concern? Yes it does, and it means we need to go further in science to establish whether there is more to this than just an association."

Dedekian says in the meantime, he hopes parents will stay focused on how much exercise their kids are getting, and what they're eating.

Regulatory agencies seem to agree that the science on BPA is far from definitive.

The FDA banned BPA from sippy cups and baby bottles this summer, but only after the plastics industry requested the action as part of an effort to reassure consumers.

A few weeks earlier, the agency rejected a call by environmental groups to remove BPA from all products that come in contact with food, saying the evidence of harm just wasn't there.

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AUDIE CORNISH, HOST:

Now, to a new study about the plastic additive BPA. The research suggests a link between BPA and the epidemic of childhood obesity, but as NPR's Jon Hamilton explains, it's too soon to say BPA can cause kids to put on weight.

JON HAMILTON, BYLINE: BPA can act like estrogen in the body. And in recent years, environmental groups have suggested it can cause everything from ADHD to prostate disease. But the science behind those allegations tends to be inconsistent and hard to interpret. And that's the case with this new study from a team at New York University.

The team looked to see whether children and adolescents with higher levels of BPA in their urine were more likely to be obese. Leonardo Trasande says that at least with white kids, they were.

LEONARDO TRASANDE: Among the children with the lowest levels of BPA, 10.3 percent were obese. While among the children with the highest levels of BPA, 22.3 percent were obese.

HAMILTON: But among black and Hispanic children and adolescents, hired BPA levels were not associated with obesity. And in none of the groups was there an association between BPA levels and being just overweight, as opposed to obese.

Trasande says those seemingly contradictory findings make it hard to draw any conclusion.

TRASANDE: When we find an association like this it can often raise more questions than answers. Clearly we need a longer-term study that examines exposure in the earliest parts of life, to see whether BPA exposure then may lead to obesity in a child.

HAMILTON: Trasande says BPA is probably most likely in to cause long-term changes in children when they are still in the womb. But he says despite the caveats surrounding the new study, it may be time to rethink childhood obesity.

TRASANDE: Diet and physical activity are still the leading factors driving the obesity epidemic in the United States. Yet, the study suggests that we need to also consider a third key component to the epidemic: environmental factors that may also contribute.

HAMILTON: Other scientists say it's hard to interpret the results of the study, which is published in the Journal of the American Medical Association. Frederica Perera, who directs the Columbia Center for Children's Environmental Health, says the team has done good research but hasn't shown whether BPA is actually causing obesity.

FREDERICA PERERA: As they point out, obese children may be simply eating and drinking foods that have higher BPA levels.

HAMILTON: So does BPA make kids obese or do obese kids just take in more BPA when they eat and drink? There's no way to know from this study. And Perera says BPA may not be the only chemical that deserves scrutiny.

PERERA: Our center has recently published a study showing that prenatal exposure to another group of endocrine disruptors, polycyclic aromatic hydrocarbons, or PAH, was associated with obesity in the children.

HAMILTON: These hydrocarbons are found in air pollution.

Mike Dedekian runs a pediatric obesity clinic at the Barbara Bush Children's Hospital in Portland, Maine. He says the new study doesn't answer the question parents are probably asking.

MIKE DEDEKIAN: So does BPA cause obesity? We don't know yet. Does this study raise our level of concern? Yes, it does. And it means we need to go further in science to establish whether or not there is more to this than just an association.

HAMILTON: Dedekian says in the meantime, he hopes parents will stay focused on diet and exercise.

DEDEKIAN: For me, we've not reached that point yet where we're starting to across the board make recommendations to patients about which products or chemicals or plastics to avoid.

HAMILTON: Regulatory agencies seem to agree. The FDA did ban BPA from Sippy Cups and baby bottles this summer. But that came after the plastics industry requested the action, as part of an effort to reassure consumers. And the FDA rejected a call by environmental groups to remove BPA from all products that come in contact with food, saying the scientific evidence of harm just wasn't there.

Jon Hamilton, NPR News. Transcript provided by NPR, Copyright NPR.