Biologists at the University of Missouri have found that a chemical commonly used in consumer plastics could affect how a body reacts to and regulates blood sugar.
Bisphenol A — or BPA — is a plastic additive found in bottles, the resin lining of food cans and thermal receipt paper. An experiment by Mizzou researchers exposed a small group of people to the chemical. After the exposure, the researchers measured subjects’ insulin levels, and found people exposed to the BPA had produced more insulin.
“In the presence of BPA as well as sugar, you have about twice the amount of insulin released relative to what you would have without the BPA,” researcher Fred vom Saal said.
Healthy bodies produce insulin in response to glucose levels in the blood. Insulin helps the body absorb that blood sugar. When a person produces too much insulin, their body needs to work more to create larger amounts of insulin. Eventually, this can lead to a condition called insulin resistance in which a person stops producing it, vom Saal said.
“At first, you release too much, and then you don’t make enough,” he said.
BPA has been a point of contention for years. Scientists know it can act similar to the hormone estrogen and can disrupt certain bodily functions. But scientists, trade groups and government agencies disagree about the amount of BPA that causes problems in humans.
Many studies have been conducted on BPA’s effects on cells. But it’s rare to have human studies of the chemical’s effects, vom Saal said. That’s what makes the new Mizzou experiment notable.
“We thought, 'That’s been shown in cell culture, but does that really happen in people?" "The answer is, 'Yes, it does,'” he said.
The federal Food and Drug Administration recently completed a large study conducted on rats that showed typical amounts of the chemical don’t cause adverse health effects.
But many academics still say BPA poses health hazards.
The American Chemistry Council, a trade group that advocates for the plastics industry, criticized the Mizzou study, saying the amount of BPA the experiment used was much larger than an amount a person would normally be exposed to.
“The dose administered in the study to human volunteers is more than 1,000 times higher than typical human exposure as repeatedly documented by large-scale biomonitoring studies from the Centers for Disease Control and Prevention and others,” the organization’s spokeswoman Kathryn St. John wrote in an email.
St. John also criticized ethics of the experiment.
“Remarkably, the authors claim that an Institutional Review Board, which is responsible for providing ethical oversight and protecting human test subjects, approved the project,” St. John wrote.
Vom Saal said the problem is continuous exposure, not a single, one-time dose of BPA. Even though it’s rapidly metabolized, many people have BPA in their bodies at any given time.
“If you look at people, they all have BPA in them; If it’s rapidly metabolized, how could that happen? The answer: there are so many ways to be exposed to this,” he said.
Vom Saal defended his experiment, saying the dose was of an amount the FDA had deemed “safe.” He said he would like to see more experiments looking at how human subjects react to BPA.
The experiment showed people with higher blood sugar are more sensitive to the chemical’s effects — an area his team would like to look into further, vom Saal said.
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