High BPA Exposure Tied To Childhood Obesity

Children with high levels of the commercial compound bisphenol A in their urine are more likely to be obese, according to a new study.

New York University School of Medicine researcher Leonardo Trasande and his colleagues examined urinary BPA levels in a sample of nearly 3,000 children and adolescents, including 1,047 children scored as overweight and 590 scored as obese. They reported their results Tuesday in the Journal of the American Medical Association.

In the U.S. exposure to BPA -- which is used to create a variety of plastics and which bears chemical similarities to the hormone estrogen -- is the norm, with 92.6 of people 6 years or older showing traces of the compound in their urine, according to one national health survey. The median urinary BPA concentration that Trasande and his colleagues found in their sample was 2.8 nanograms per milliliter.

After controlling for factors like age, race, income level, and sex, a clear pattern emerged. A little over 10% of the children in the bottom quarter of BPA levels were estimated to be obese. For children in the next quartile, that figure was 20.1%; in the third quartile, it was 19%. And in the top quartile - the children with the highest levels of BPA in their urine - more than 22% were obese.

Compared to the group of children with the lowest BPA concentration, children in the upper quartile were 2.6 more likely to be obese.

"To our knowledge, this is the first report of an association of an environmental chemical exposure with childhood obesity in a nationally representative sample," the authors wrote.

In further analysis, the authors found their results were statistically significant only in white children and adolescents.

Admittedly, the data shown in this study is correlation, not causation - there is not yet solid proof that BPA actually made the children to gain weight.

But much research already shows that BPA can disrupt normal metabolic processes in people and even possibly change gene expression patterns in mice. Studies have tied BPA's estrogen-like characteristics disorders with roots in abnormal sensitivity to estrogen, like breast cancer.

The U.S. Food and Drug Administration recently banned BPA use in baby bottles and sippy cups, but Trasande and his colleagues say their work shows that looking at BPA content in other products used by older children.

"Last year, the FDA declined to ban BPA in aluminum cans and other food packaging, announcing 'reasonable steps to reduce human exposure to BPA in the human food supply' and noting that it will continue to consider evidence on the safety of the chemical," the authors wrote. "Carefully conducted longitudinal studies that assess the associations identified here will yield evidence many years in the future."

SOURCE: Trasande et al. "Association Between Urinary Bisphenol A Concentration and Obseity Prevalence in Children and Adolescents." JAMA 308: 1113-1121, 19 September 2012.