CORRECTION: An earlier version of this story mischaracterized how much BPA went up in urine levels. BPA levels increased 1,000 percent. It also misquoted Jenny Carwile in the 14th paragraph.
Researchers trying to figure out whether a common chemical called BPA is a threat to health said on Tuesday they found evidence that at least one food—canned soup—could be a major source.
People who ate a can of soup a day for five days had a 1,000 percent increase in the usual levels of BPA in their urine, the team reported in the Journal of the American Medical Association.
What’s not clear is if this means the body efficiently gets rid of the chemical and thus it’s less of a worry than thought, or whether it means the chemical is more of a threat because so much of it is at least passing through.
"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. This study suggests that canned foods may be an even greater concern, especially given their wide use," Jenny Carwile of the Harvard School of Public Health, who led the study, said in a statement.
Carwile told National Journal that her team was surprised to see such a huge increase in urinary BPA after just a few days of eating canned soup.
Bisphenol A is found in the lining of food and beverage cans and in some plastic containers. It's found in just about everyone's body, and some studies have linked higher levels to diabetes, heart disease, and obesity in humans, and to disrupted sexual development in animals.
Canada has declared BPA a toxic chemical, and the National Toxicology Program at the Health and Human Services Department has stated “some concern for effects on the brain, behavior, and prostate gland in fetuses, infants, and children at current human exposures to bisphenol A.”
However, the Food and Drug Administration is currently supporting further study rather than recommending any new regulation of BPA. FDA says it’s not clear what harm the chemical does or even whether it lingers in human tissues.
For the experiment, Carwile’s team divided 75 student and staff volunteers into two groups. The first group drank a 12-ounce serving of fresh vegetarian soup, made with no canned ingredients, every day for five days. The second group drank a serving of Progresso brand vegetarian soup every day for five days.
Urine samples were taken on the fourth and fifth days of the study, combined, then tested for BPA. After a two-day "washout" period, the groups switched and the study repeated.
Urine samples collected after a week of drinking canned soup revealed, on average, a 1,221-percent increase in urinary BPA compared to samples collected after a week of drinking fresh soup, the researchers found. Even during the non-canned soup week, BPA was detected in 77 percent of samples. All urine samples from participants who drank canned soup daily contained BPA.
Carwile noted that urinary BPA levels decreased significantly over the two-day break period, a finding that suggests that the body doesn’t hold on to the chemical for long.
“I think we need more studies that are really following people hour by hour and day by day,” she said, noting that some of the illnesses linked to BPA take a lifetime to develop. Studies that measure BPA levels in the bloodstream might provide a better measure of BPA retention within the body, she added.
“We can't say for sure if BPA built up in the body with each day of canned soup consumption,” Carwile said. BPA levels may have spiked in the volunteers because they ate soup that day and may not have been high because they ate soup for a week.
The study does not prove that BPA can hurt people, but it does back up research suggesting that Americans may be ingesting more of the compound than they realize. Americans are likely exposed to higher levels of BPA than the Environmental Protection Agency deems safe, a 2008 study by British-based researchers found.
Vegetable-based alternatives to BPA can linings exist, Carwile said, but in order to reduce BPA exposure it might be best to limit eating canned foods. “Fresh and frozen foods, I think, are a great alternative,” she said.
The American Chemisty Council, an industry group, argues on its website that “the potential human exposure to BPA from polycarbonate plastic and epoxy resin food contact applications is minimal and poses no known risk to human health.”