New study finds that chemical used in the lining of soda and soup cans could be linked to diabetes and heart disease

Volunteers who ate a can of soup five days a week had more than 1,000 times the chemical bisphenol A (BPA) in their urine as those who ate fresh soup, according to a study by the Harvard School of Public Health. The chemical has been linked to heart disease and diabetes.

It's among the first attempts to determine BPA levels in people after they've eaten canned goods, say the researchers, some of whom had already documented levels in certain plastic drinking bottles. Their findings were just published in the Journal of the American Medical Association.

Besides heart disease and diabetes, obesity has also been linked by research to the chemical BPA. It is used in the lining of metal and beverage cans and is found in polycarbonate bottles (recycling number 7) and dental composites and sealants, the researchers noted.

"Previous studies have linked elevated BPA levels with adverse health effects. The next step was to figure out how people are getting exposed to BPA. 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," said Jenny Carwile, lead author and a doctoral students in Harvard's Department of Epidemiology.

Study subjects were volunteer students and staff at the public health school, who were divided into groups to consume either canned soup five days a week or fresh soup. After a two-day "washout" period, they switched assignments.

Urine samples of the 75 volunteers found that those who consumed canned soup for five days saw a 1,221 percent increase in BPA compared to levels in urine after the subjects ate fresh soup. It was elevated after a single day's consumption.

They emphasized that the concentrations may be temporary and that further study is needed to see how long the BPA levels linger.

"The magnitude of the rise in urinary BPA we observed after just one serving of soup was unexpected and may be of concern among individuals who regularly consume foods from cans or drink several canned beverages daily," said senior author Karin Michels, associate professor in the Department of Epidemiology, in a release announcing the research. "It may be advisable for manufacturers to consider eliminating BPA from can linings."

Bisphenol A is an organic compound used in polycarbonate plastic and epoxy resins, as well as to line cans so they don't corrode. It can mimic the effects of the human hormone estrogen, notes Medical News Today, and is considered an endocrine disruptor. Studies have noted that it interferes with reproductive development.

The U.S. Food and Drug Administration has expressed concerns that exposure to BPA may be especially harmful to fetuses, infants and young children. Canada actually declared it a toxic substance last year. And Europe and Canada have banned it in baby bottles, while the FDA says it supports "the industry's actions to stop producing BPA-containing baby bottles and infant feeding cups for the U.S. market," as well as helping to find alternatives to BPA in can linings and other applications.

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