Wednesday, September 26, 2012

BPA and Childhood Obesity

Last week a scientific article in the Journal of the American Medical Association indicated that there is an association between childhood obesity and bisphenol A (BPA), a plastic used to coat the inside of food cans. The authors of the report measured the concentrations of BPA in urine (a rough measure of BPA exposure) in over 2,800 children. They found that the most obese quartile of the children also had the highest levels of urinary BPA. The authors were quick to point out (correctly) that the observed association between obesity and high concentrations of BPA does not prove that BPA causes obesity. Although the findings are certainly intriguing, there are other possible explanations. For example, perhaps the obese children were obese because they ate more food (ingested more calories) from containers lined with BPA, so that their high BPA levels are just a consequence of where they got their calories. Or perhaps obese children store more BPA in their fat. Incidentally, the authors based their findings on data obtained from questionnaires, a notoriously poor way to obtain accurate information about dietary intake.

In science, words matter.  The headlines of most popular press news coverage of the JAMA article correctly used phrases like “an association” or “a link” to describe the relationship between obesity and BPA. Others were not so careful; the headline in the International Business Times was “BPA Causes Obesity in Children, New Study Shows”.

Unfortunately, such sloppy (or agenda-driven) reporting of science news only scares and confuses consumers. The American Chemistry Society, admittedly a group that itself might have an agenda, felt obligated to issue a press release on BPA this week, pointing out that the study’s authors themselves stated “…causation cannot be inferred from a cross-sectional association…”.

I’m not trying to defend BPA; frankly I think the jury is still out concerning its risk to human health. In the face of uncertainty, though, there’s nothing wrong with deciding to err on the side of caution and cutting down on the use of BPA in food containers, especially if suitable substitutes can be found. For example, BPA has already been removed from babies’ bottles. But the American Chemisty Society is right; the evidence presented in the most recent study does not prove that BPA causes or even contributes to childhood obesity. This time, the International Business Times just plain got it wrong.

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