Research led by Jennifer Hartle, a postdoctoral researcher at the Stanford Prevention Research Center, has confirmed the link between canned foods and Bisphenol A (BPA), a chemical associated with health problems.
Hartle co-authored the study, published June 8 in Environmental Research, with Ana Navas-Acien and Robert Lawrence of Johns Hopkins University.
Consumption of BPA-contaminated foods has been implicated in childhood obesity, diabetes, cardiovascular disease and other health issues. In the U.S., the Food and Drug Administration (FDA) and Environmental Protection Agency (EPA) consider an oral dose of BPA higher than 50 micrograms per kilogram of body weight to be harmful. The EU’s maximum acceptable oral dose is much lower, at 4 micrograms per kilogram of body weight.
Previously, Hartle showed that children are exposed to BPA at higher levels due to the chemical’s presence in school lunch packaging. Because children are still growing, the hormone imbalance that BPA causes can be particularly disruptive in their development. Hartle’s work on lunch packaging led her to canned foods.
When Hartle and her co-authors began their research in 2011, a connection between BPA and canned foods was known; what was not known, however, was how much of the BPA in the body came from canned foods in one’s diet.
“We think that [BPA] could have came from environmental factors as well: It’s found in air, dust, soil, [touching plastic] that has BPA on it,” Hartle said.
Using three different surveys collected by the National Health and Nutrition Examination Survey (NHANES) from 2003-08, Hartle and her co-authors analyzed what patients had eaten in the 24 hours before giving urinary and blood samples. The researchers found that 92.6 percent of the U.S. population had measurable levels of BPA.
“That’s when the concern really grew, because that is a huge number,” Hartle said. “For any environmental contamination, 92.6 percent means almost every single person has BPA in their system.”
Hartle discovered that even with environmental factors and other sources of BPA exposure accounted for, there was still a significant correlation between canned foods consumption and the chemical in one’s urine concentrations.
BPA is found in the resin of a can’s lining. Because cans can vary widely by company and food type, the amount of BPA in canned foods can also vary. Research has shown that foods that require more heating in the canning process are most susceptible to BPA.
“BPA is lipophilic,” Hartle said. “It’s very drawn to the fat, and so often times you’ll find higher levels of BPA in cans of meat and other kinds of fatty foods.”
Canned soups, for example, have a high concentration of BPA. Because soup is a heterogeneous mixture of solids and liquids, it takes longer to heat all of the components to the same temperature. This, in addition to soup’s usually high fat content, causes high BPA concentration.
Despite the clear connection between canned foods and BPA, manufacturers currently have no legal obligation to change the composition of cans’ linings. While some water bottles or cans state that their contents are BPA-free, consumers cannot know if these claims are actually true. There is no official certification or qualification that can manufacturers can receive. Different brands disclose different levels of information; according to Harle, some companies like Muir Glen or Eden Foods are more transparent in what they share.
“They have gone in or they have paid to have analysis,” Hartle said. “Can manufacturers still don’t have to disclose [anything], but some companies know that people will stop buying their products if they’re not clear what the cans are made of.”
Hartle offers a two-part solution to minimize one’s exposure to BPA. She advises people to eat fresh fruits and vegetables with no packaging as well as to become advocates for food safety.
“Call can manufacturers,” Hartle said. “They keep track of how many people are calling. [Tell them that] we want not just BPA-free cans, but we want safe cans. So we want to know if any alternatives are safe.”
Contact Hannan Waliullah at htwailiulah ‘at’ gmail.com.