Among the most ubiquitous and scrutinized of these so-called endocrine disruptors is bisphenol, better known as BPA. The chemical is a common ingredient in plastics and food-can linings.
Angel Nadal, a BPA expert at the Miguel Hernandez University in Spain stated that, "When you eat something with BPA, it's like telling your organs that you are eating more than you are really eating."
Nadal's latest research, finds that the chemical triggers the release of almost double the insulin actually needed to break down food. High insulin levels can desensitize the body to the hormone over time, which in some people may then lead to weight gain and Type 2 diabetes.
To achieve this feat, BPA fools a receptor into thinking it is the natural hormone estrogen, an insulin regulator. Nadal's team found that even the tiniest amounts of BPA -- a quarter of a billionth of a gram -- did the trick. The effect disappeared when the researchers stripped the specific receptors from the study mice, evidence that they had in fact pinpointed BPA's chemical mechanism, which had previously eluded scientists. In laboratory tests of human cells, the response was even more pronounced.
"That pretty much nails it," Bruce Blumberg of the University of California, Irvine, who was not involved in the new study, told The Huffington Post. He notes that despite the prior associations made between BPA and metabolic problems, including obesity and diabetes, doubt had lingered because of a lack of understanding about how the phenomenon occurred. Long-term studies of children -- tracking BPA exposures and health outcomes -- remain ongoing around the world.
An estimated 90 percent of people in developed countries have BPA circulating in their blood at levels often higher than the threshold for causing hormone disruption used in Nadal's study. This high incidence is due not only to exposures from leaching food packages but also BPA-infused cash register receipts, dental sealants and toilet paper.
Frederick vom Saal, another expert in endocrine disruptors at the University of Missouri-Columbia stated that, "People are seeing effects of BPA down to 1000-fold below [Nadal's threshold]." "It takes so little of this chemical to cause harm."
Published in PLoS ONE, Feb 2012