The study suggests that canned soups and pasta can expose consumers to higher concentrations of BPA than canned vegetables and fruit -- and although those foods are tied to BPA concentrations, canned beverages, meat and fish are not.
"This knowledge can help guide consumers when making decisions as to which canned products they choose to buy," said Deborah Kurrasch, an assistant professor at the University of Calgary Cumming School of Medicine who was not involved in the study.
"I am not surprised by these research findings, as others have shown that consuming canned foods is one of the highest routes of exposure to BPA," she said. "This study serves to illustrate that consuming canned foods continues to be a source of contamination."
The study included data collected on 7,669 people, ages 6 and older, in the United States between 2003 and 2008 as part of the National Health and Nutrition Examination Survey
The researchers analyzed the data, which indicated what each person had eaten in the past 24 hours as well as whether BPA concentrations were detected in each person's urine on the same day.
"Urinary BPA concentrations are evidence of BPA exposure," said Jennifer Hartle, postdoctoral research fellow at Stanford University School of Medicine and lead author of the study.
The researchers found that people who consumed one canned food item in the past day had about 24% higher concentrations of BPA in their urine compared with those who had not consumed canned food. The consumption of two or more canned food items resulted in about 54% higher concentrations of BPA.
"We could see a clear association with canned foods," Hartle said.
Cream of mushroom vs. canned peaches
Once the researchers evaluated what types of canned foods were consumed, they found that eating canned soup resulted in a whopping 229% higher concentration of BPA compared with consuming no canned foods. Canned pasta resulted in 70% higher concentrations, and canned vegetables or fruit resulted in 41% higher concentrations.
Someone who eats a single can of cream of mushroom soup may still have a greater exposure to BPA than someone who eats three cans of peaches, Hartle explained.
But why exactly might canned soup result in higher BPA concentrations than other foods? Hartle said it might have something to do with how much heating soup requires when it is processed, and it tends to have a higher amount of fat.
"A canned soup -- which oftentimes is solid and a liquid -- usually needs a long heating time to get all of the contents to the same temperature needed to sterilize the food. Many canned beverages (beer, soda, juice) are acidic, so their thermal processing requirement is much different," she said. "Another factor is that BPA partitions to, or moves into, solids. ... Other key factors are the chemical composition of the lining and the fat content of the canned food, as BPA is lipophilic."
Scientists have continued to examine whether BPA exposure from canned foods poses a health risk. The concern stems from how BPA can hack and disrupt the normal responses of hormones in the body. For instance, it can mimic the effects of estrogen. In doing so, it can reprogram cells, causing a plethora of health problems.
"BPA exposure is associated with many adverse health effects including diabetes, obesity, cardiovascular disease, reproductive development issues, amongst others," Hartle said.
A report released in March by non-governmental organizations in the United States and Canada, including the Breast Cancer Fund, found that about two out of three cans
commonly found on grocery shelves test positive for BPA.
However, the overall BPA exposure that results from canned foods remains low, said John Rost, chairman of the North American Metal Packaging Alliance.
"It's important for consumers to realize that these levels are well below a 'part per million' in their food," he said. "It is also important to note that recent reviews by FDA, the European Food Safety Authority, Health Canada and other regulatory bodies have shown that current exposures to BPA are safe for all consumers regardless of age or gender."
'It's the type of dataset that the field really needs'
While regulators worldwide offer different thresholds for what a safe BPA dosage is, the Environmental Protection Agency notes that exposure to BPA should not exceed
50 micrograms per kilograms of body weight each day.
Lauren Sucher, a spokeswoman for the Food and Drug Administration, said in a statement to CNN, "The FDA has performed extensive research and reviewed hundreds of studies about BPA's safety, and has determined that current authorized uses of BPA in food packaging are safe
. The FDA continues to monitor literature and research on BPA."
Additionally, she said, many studies on the chemical have a high potential for contamination, which may skew study results to show higher concentrations of BPA than what's really there, since BPA is widespread in our environment.
Still, the primary way people are exposed to BPA is through diet, according to the National Institute of Environmental Health Sciences
. BPA can exit our bodies through bodily fluids, primarily urine.
The chemical is no longer used in baby bottles and sippy cups in the United States, and Hartle advises, "People can reduce their exposure to BPA by choosing fresh, unpackaged foods whenever possible."
The new study adds a huge data component to the continuing BPA discussion, said Gail Prins, professor of urology, physiology and environmental health at the University of Illinois at Chicago, who was not involved in the study.
"There has been contradictory data put out there, and this particular dataset is definitive in my mind," she said. "It's the type of dataset that the field really needs, and it's important because it does show that what we eat is affecting our BPA levels."