Study linking BPA and childhood obesity shows no causal relationship
October 8, 2012
A new study has reported a statistical association between urinary levels of bisphenol A (BPA) and obesity in children, but the authors acknowledge that the study does not indicate a causal relationship. They further state that their study was "at best hypothesis generating" indicating that the study results are speculative and, at most, might provide the basis for conducting additional studies.
The cross-sectional study, * the results of which were published in the Journal of the American Medical Association (JAMA), analyzed a randomly selected, national sample of 2,838 young people ages 6-19, whose urinary BPA concentration had been measured in the 2003-08 National Health and Nutrition Examination Surveys. After controlling for factors including race, age, income, caloric intake and television watching, the researchers analyzed the connections between urinary BPA concentration and body mass index (BMI). They found that higher BPA levels were "significantly associated" with BMI measures that indicated obesity.
The researchers acknowledge, however, that obesity is a complex disease that develops over time, and that they cannot infer from the study that any level of BPA intake causes obesity. This is not surprising, given the study's fundamental limitations and that numerous other studies conducted on animals exposed to BPA have found no consistent effect on body weight.
The authors comment extensively on possible explanations for their findings. They state that the time of urine collection might influence BPA concentration. Furthermore, they concede that they do not know what foods were consumed by the children in the study.
"Obese children may drink more canned or bottled beverages, or eat more canned food, and thus have higher urinary BPA levels," they write. The researchers also state that the BPA-obesity correlation was found among Caucasian children but not black or Hispanic youngsters-a fact that seems to further cloud the issue of causation.
"More relevant to actual, real-world safety is the recent, robust research funded by the Environmental Protection Agency and conducted by scientists at the government's Pacific Northwest National Laboratory, Centers for Disease Control and Prevention and Food and Drug Administration," commented Steven G. Hentges, Ph.D., of the Polycarbonate/BPA Global Group of the American Chemistry Council. "Consistent with previous human and animal studies, the Pacific Northwest study (Teeguarden et al.) indicates that, because of the way BPA is processed in the body, it is very unlikely that BPA could cause health effects at any realistic exposure level.
"Attempts to link our national obesity problem to minute exposures to chemicals found in common, everyday products are a distraction from the real efforts underway to address this important national health issue," Hentges said.
* Trasande, L, et al. Association Between Urinary Bisphenol A Concentration and Obesity Prevalence in Children and Adolescents. JAMA 2012; 308(11:1113-1121)