September 18, 2012

expert reaction to bisphenol A and childhood obesity

A study in JAMA showed children who had higher concentrations of urinary bisphenol A (BPA), a manufactured chemical found in consumer products, had significantly increased odds of being obese.

Prof Richard Sharpe, MRC Centre for Reproductive Health at The University of Edinburgh, said:

“The study shows an association between exposure to bisphenol A and the occurrence of obesity in white children (not in Hispanic or Black children). The study is scientifically robust and its interpretation is admirably restrained and accurate. The points that I make below are important, but are also made by the authors themselves in their paper.

“This study does not prove that increased exposure to bisphenol A causes obesity, only that the two are associated.  Such an association could arise because children who are obese choose to eat more of foods (e.g. canned drinks/foods) that contain more bisphenol A than do non-obese children, or that bisphenol A metabolism is altered by being obese, so that levels appear higher in fatter children.  One unusual observation is that the association only applies to white children. As the prevalence of obesity is generally higher in black than in white children in the USA, this would certainly argue against bisphenol A as being an important cause of the childhood obesity crisis.

“Diet accounts for >95% of human exposure to bisphenol A.  As we know that (poor) diet is a critically important determinant of childhood obesity, it still seems intuitively more likely that diet is determining both obesity and the level of bisphenol A, hence their association.  This would fit with the evidence that most bisphenol A is rapidly inactivated upon ingestion, effectively preventing exposure of most body tissues outside of the gut.  Nevertheless, the possibility that bisphenol A exposure could causally contribute to obesity cannot be dismissed, even if it seems unlikely (for the reasons mentioned).”

Prof David Coggon, Professor of Occupational and Environmental Medicine at the University of Southampton, said:

“The findings are consistent with a similar study carried out previously in adults.  They are unlikely to have occurred by chance, but it remains uncertain whether higher exposure to BPA causes obesity. 

“Other possibilities are that children with low intakes of BPA also have lifestyles which render them less prone to put on weight (although the researchers made strong efforts for control for this), or that obesity leads to changes in diet with greater exposure to sources of BPA. 

“Further research is needed to establish whether consistently high excretion of BPA is associated with increases in body mass index over time, and to understand better the temporal relationship between dietary exposure to BPA and excretion of the compound in the urine.”

‘Association Between Urinary Bisphenol A Concentration and Obesity Prevalence in Children and Adolescents’ by Leonardo Trasande et al. published in the Journal of the American Medical Association on Tuesday 17^th September.