BPA Is Bad to the Bone, Now We Know Why

BPA is no friend to the American consumer. The industrial chemical bisphenol A, found in thousands of commercial products, has been linked with reproductive problems, brain impairments, cancer, obesity and more. But now, scientists believe they've found another piece of the puzzle explaining how the chemical wreaks havoc on our health.

San Diego scientists created a 3-D computer model of the chemical and one of its breakdown products. In the process, they figured out why this breakdown product, called a metabolite, is more active than BPA, causing even further damage to our bodies.

"We discovered the mechanism by which it's so much more active than the BPA," Michael E. Baker, a research professor at the University of California San Diego who led the study, told TakePart.

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Scientists already know that BPA mimics estrogen and attaches itself to estrogen receptors in the body. That causes estrogen levels to change, a process that could be linked to health problems.

In the new computer model, Baker discovered that a BPA metabolite, known as MBP, is longer and can attach itself to both ends of an estrogen receptor. The BPA molecule is shorter and can only attach at one end.

"In other words, MBP is basically grabbing onto the estrogen receptor with two hands compared to just one hand for BPA,"  Baker says. "Two contact points makes a much stronger connection."

There was a bonus in the new discovery, published online this week in the journal PLOS ONE: this may point the way to the development of a new class of drugs to hamper the excess estrogen activity linked to diseases such as certain breast cancers, Baker says.

"If a chemist could find a way to have the metabolite bind to the [estrogen] receptor but not have any activity," Baker says, that might pave the way for developing a drug that would hamper excess estrogen production.

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For the new research, Baker built on work done in 2004 by Shin'ichi Yoshihara and colleagues from Hiroshima International University in Japan. The Japanese scientists discovered the production of MBP when the BPA was metabolized. They found that MBP bonded more strongly to the estrogen receptor, but did not go on to try to explain why, Baker says.

So Baker took up the challenge,  conducting the new research with Charlie Chandsawangbhuwana, a UCSD graduate student.

The MBP metabolite that Baker found to be so active may be just one of several, he says. "If one metabolite can have this much potency, maybe others are [even] more active."

Baker sees another potential application of the research, besides new drug development. Researchers who are continuing to evaluate the ill effects of BPA exposure on health may consider measuring the MBP metabolite in the urine, just as they currently measure the BPA, Baker says.

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That information could give them more understanding of the BPA-health problem links and what role BPA or its metabolites may play.

Studies suggest that BPA is found in the urine of most Americans, according to the Centers for Disease Control and Prevention, proving almost everyone is exposed. Although the Food and Drug Administration has banned BPA in baby bottles and sippy cups and many manufacturers are halting the sale of BPA-based products, the chemical can still be found in thousands of products ranging from eyeglasses and computer equipment to food packaging.

Eliminating exposure to BPA is probably not possible, according to the Environmental Working Group, which researches health risks and has reported extensively on BPA. The EWG says steps can be taken, however, to reduce exposure. For example, rinse food from cans before eating or heating. Choose ceramic, glass or other microwave-friendly dishes, instead of plastic.

The FDA says concerned consumers can cut down on BPA exposure by not using plastic containers with recycle codes 3 or 7 and avoiding bottles with scratches. The agency is continuing to evaluate the evidence about any health risks from low-dose BPA exposure. Previously it said the trace BPA contamination found in foods and beverages is safe.

Do you think all products with BPA should be banned? Let us know in the comments.

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Kathleen Doheny is a Los Angeles journalist who writes about health. She doesn't believe inmiracle cures, but continues to hope someone will discover a way for joggers to maintain their pace.