The modern lifestyle of super-sized french fries and couch potatoes often takes the blame for the rising rates of obesity and diabetes in the U.S. -- perhaps rightly so. But growing evidence suggests another factor in the dual epidemics: modern chemicals.
Exposure to even minuscule amounts of synthesized substances -- used in everything from pesticides to water bottles -- can scramble hormone signals, scientists say. This interference can trick fat cells into taking in more fat or mislead the pancreas into secreting excess insulin, a hormone that regulates the breakdown of fat and carbohydrates.
Among the most ubiquitous and scrutinized of these so-called endocrine disruptors is bisphenol A, better known as BPA. The chemical is a common ingredient in plastics and food-can linings.
"When you eat something with BPA, it's like telling your organs that you are eating more than you are really eating," says Angel Nadal, a BPA expert at the Miguel Hernandez University in Spain.
Nadal's latest research, published last week in PLoS ONE, 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.
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