Nov. 22, 2011 -- Eating just one 12-ounce serving of canned soup a day for five days straight may lead to more than a 1,000% increase in the amount of the controversial chemical bisphenol A (BPA) in your urine, a new study shows.
BPA is a chemical used in the manufacturing of many metal food and beverage cans, among other uses.
The canned soup study did not look at how -- or even if -- the BPA spike in urine affects health. This is a major sticking point for many critics of the study who caution against overinterpreting the findings.
Because of health concerns, many companies have taken steps to eliminate BPA from baby bottles and sippy cups, and others are looking into alternatives to BPA for their products.
As part of the new study, 75 volunteers ate either a 12-ounce serving of vegetarian canned soup every day for five days or a 12-ounce serving of non-canned, fresh vegetarian soup for five straight days.
After a two-day wash-out period, participants switched groups. "After just five days of canned food consumption, there was more than a 1,000% increase of BPA in urine," says study researcher Jenny L. Carwile. She is a doctoral student in epidemiology at the Harvard School of Public Health in Boston.
The study is published in TheJournal of the American Medical Association.
The findings likely represent a temporary peak in BPA levels. Researchers do not know how long this peak lasts or what type of effects it may have on health.
Although the canned soup used in the study was a single brand, Progresso, "it is not about the brand of soup or canned soup, it is about the cans," Carwile says. She says the findings likely apply to other canned foods that use BPA in the liner.
Reducing BPA Exposure
"If somebody is interested in reducing BPA, they can do it by reducing canned food consumption" Carwile says.
Still, canned food "is cheap, convenient, and can be healthy when it is low in sodium," she tells WebMD. "[But] fresh and frozen foods may offer the same health benefits minus the BPA exposure."
Ted Schettler, MD, MPH, is the science director of the Science and Environmental Health Network, a public and environmental health advocacy group. He reviewed the findings for WebMD. "The numbers are dramatic," he says. "BPA levels go way up when you eat canned soup."
And while Schettler says the way they measured the BPA may not be the best way to fully show the amount of BPA throughout the body, "these spikes may be important and at some point we have to decide since we do have alternatives," he says. BPA-free alternatives including natural oils and resins are beings studied, and can also be used as an alternative to BPA in metal can linings.
A study released last week by the Breast Cancer Fund found BPA in many of the canned foods that we associate with Thanksgiving. "Many canned foods beyond soups, including those used in popular Thanksgiving dishes, contain BPA," says Sharima Rasanayagam, PhD, the director of science at the Breast Cancer Fund in San Francisco.
"When you think of the possible daily exposure to BPA from canned foods, you start to see the urgency of getting this chemical out of food cans," she says in a statement.
"There's no controversy that canned goods contain trace levels of BPA to properly seal the can to prevent botulism," says Jeff Stier. He is a senior fellow at the National Center for Public Policy Research, a conservative think tank based in Washington, D.C. "It is no surprise that daily consumption would increase trace levels of BPA in the urine over the short term."
"[But] this small ... study does nothing to substantiate claims that trace levels of BPA -- even from daily canned soup consumption -- have any effect on health," he tells WebMD.
Stier's sentiments are echoed by John Rost, PhD. He is the chairman of the North American Metal Packaging Alliance, Inc., an industry trade organization representing metal packaging manufacturers.
"The presence of BPA, as reported by this study, gives consumers no new information about health effects from BPA exposure from canned foods," Rost says in a statement. "The presence of BPA in the urine does not indicate a health risk. In fact, what this study does confirm for consumers is that BPA is quickly excreted from the body through urine."
"Consumers need to remember that BPA-based [linings] are used to keep food safe by enabling high-temperature sterilization that eliminates the dangers of food poisoning and maintains the integrity of the can for continued protection against contaminants."