Their study, published in this week's Journal of the American Medical Association, found that a group of volunteers who consumed a serving of canned soup every day for 5 days had a 1,000% increase in bisphenol A (BPA) concentrations in their urine, compared to those who ate fresh soup.
BPA is used in the lining of metal food and beverage cans, because it resists corrosion and heat. It is also used in polycarbonate hard plastic bottles (identified by the recycling number 7), as well as dental sealants.
It has been shown to interfere with hormones, including estrogen. BPA has been shown to interfere with reproductive development in animals, and has been linked to cardiovascular disease, diabetes, and obesity in humans.
In the Harvard test, urine samples of 75 volunteers who ate canned soup daily had BPA levels 1221% higher than those who ate the fresh soup.
Senior author Karin Michels, an associate professor in the Department of Epidemiology, says the size of the rise in BPA with just one serving of soup daily was a big surprise. She said it may be of concern for people who regularly eat canned food or drink several canned beverages every daily.
The researchers say the rise may be short-lived, but that will have to be determined in a future study.