People who eat canned versus homemade soup consume high levels of bisphenol A (BPA), according to research released Tuesday about the controversial plastic-hardener linked to developmental disruptions in children along with cancer, diabetes and heart disease in adults.
After volunteers ate canned or homemade soup once a day for five days, those who needed can openers for their meals had 20 times as much BPA in their urine, according to the study published in the online edition of the Journal of the Medical Association on Tuesday. Typically, metal cans are lined with plastic that contain the plastic additive.
The magnitude of the rise in urinary BPA we observed after just one serving of soup was unexpected and may be of concern among individuals who regularly consume foods from cans or drink several canned beverages daily, said Karin Michels, an epidemiologist at the Harvard School of Public Health who headed the study. It may be advisable for manufacturers to consider eliminating BPA from can linings.
However, researchers and consultants for the canning industry disagreed with the findings and said that the increased levels of BPA in urine attests to the body's rapid elimination of the chemical.
This study adds to the body of evidence that demonstrates that current human exposures to BPA will not result in health effects in the population, Julie Goodman, a toxicologist and industry consultant who teaches at the Harvard School of Public Health, wrote in an email.
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Members of the chemical and plastics industry advocate use of the plastics-additive that U.S. regulators are currently re-examining. Canada completely banned the chemical in 2010, and China and the European Union and banned the chemical from baby bottles in 2011, but U.S. manufacturers still use the chemical. U.S. Sen. Dianne Feinstein, D-Calif., introduced legislation in January that would have banned BPA from infant food containers, a measure that did not pass.
Goodman wrote that elevated levels of BPA in urine showed that humans rapidly eliminated the chemical. While [lead author Jenny] Carwile and her colleagues emphasized the difference between BPA in urine after eating fresh and canned soup, they did not evaluate the health risks of these exposures. In fact, this study shows that even after a can of soup, human exposures are much lower than levels of BPA that have been demonstrated to cause effects in animals, Goodman said.
The research, funded through the National Institute of Environmental Health Science and a grant from the nutrition research-focused Allen Foundation, included 75 volunteers who ate vegetarian soup either canned or fresh soup for five days, took a two day break and then ate the reverse option.
The researchers measured BPA levels in the volunteers' urine and found a 1,221 percent increase in BPA in those who had eaten canned soup compared to those who had eaten fresh soup.
We've known for a while that drinking beverages that have been stored in certain hard plastics can increase the amount of BPA in your body, doctoral student Carwile said in a statement. This study suggests that canned foods may be an even greater concern, especially given their wide use.
How BPA affects humans remains controversial as researchers push for its ban citing its role as a human hormone interrupter, even as manufacturers argue that the chemical is harmless and necessary.
Increased BPA concentrations correlated with increases in anxiety and depression in 3-year-old children, according to a study published in October in the journal Pediatrics.
Clinicians may advise concerned patients to reduce their exposure to certain consumer products, but the benefits of such reductions are unclear, the researchers concluded.
The American Chemistry Council rebutted that because of the way BPA is processed in the body, it is very unlikely that BPA could cause health effects at any realistic exposure level.
Both ACC and Goodman cited a study in support of BPA from the Pacific Northwest National Laboratory in Richmond, Wash. The authors exposed volunteers from one to four times the average level of BPA in the American diet and found that while BPA levels in urine increased, levels in the blood serum stayed similar. Justin Teeguarden, a federal scientist, led the study published in the journal Toxicological Sciences in September.
A month later, Frederick S. vom Saal, a biologist at the University of Missouri in Columbia, Mo. and colleagues called the research not only fatally flawed, but wrote in an editorial in Toxicological Sciences that the authors misrepresented previous literature on the BPA exposure.
Teeguarden and colleagues blasted back. Their letter is instructive principally as a showcase for the unscientific tactics they are willing to use, a behavior we are not the first to identify and criticize, the original researchers wrote.
The back and forth between the two research groups did not involve the research released Tuesday, but shows how contentious the issue of BPA can be.
The observed increase in urinary BPA concentrations following canned soup consumption, even if not sustained, may be important, especially in light of available or proposed alternatives to epoxy resins linings for most canned goods, the authors concluded.