Volunteers who had one can of soup per day for five days had urine BPA (bisphenol A) levels rise by over 1,221% compared to the same people who had consumed freshly made soup daily for five days, researchers from Harvard School of Public Health reported in JAMA (Journal of the American Medical Association). The authors say their study is one of the few to measure human BPA levels after consuming canned products.

Lead author, doctoral student, Jenny Carwile, who studies at the faculty’s Department of Epidemiology, said:

“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.”

Bisphenol A or BPA, molecular formula C15H16O2, is an organic compound that is used to make polycarbonate plastic and epoxy resins, among other things. BPA is an estrogenic – it has properties which can mimic the effects of the human hormone estrogen – it is an endocrine disruptor.

BPA is added to the lining of foods and drinks cans and, according to studies, interferes with reproductive development in animals, including humans. BPA levels in humans have been associated with a higher risk of developing several diseases and conditions, including obesity, diabetes type 2, and cardiovascular diseases.

BPA has also been found in polycarbonate bottles, which are identified by recycling number seven, as well as dentistry sealants and composites.

In 2008, concern regarding BPA became a public theme in the media after the governments of several nations questioned its safety – many retailers in North America, Western Europe, Japan and Australasia made moves to remove BPA-containing food products from their shelves.

A 2010 US FDA (Food and Drug Administration) report expressed concern regarding exposure of BPA to fetuses, infants and young children. Canadian authorities declared BPA a toxic substance in 2010 – the first country to do so. BPA is banned in baby bottles in the European Union and Canada.

Prenatal exposure to BPA has been associated with subsequent neurological difficulties.

Jenny Carwile and Karin Michels set out to determine whether the consumption of canned soup might raise concentrations of urinary BPA, compared to the consumption of freshly-made soup.

Their 75 volunteers consisted of students and staff from the Harvard School of Public Health. They were divided into two groups:

  • One group ate a 12-ounce serving of canned soup (vegetarian), one a day for five days. Then they washed-out for two days. This was followed by a same-sized portion of 100% freshly-made soup once a day for five days.
  • The other group did the same, but the other way round; starting off with daily freshly made soup, followed by a two-day washout, and then five days of daily canned soup.

The urine sample results from the two groups were similar, and showed that at the end of the five days on canned soups their HPA urine concentrations were 1,221% higher, compared to levels at the end of five days on freshly-made soup.

Further studies are required to determine how long urine levels remain high, the researchers stressed. They suspect the higher BPA levels may be temporary.

Senior author, Karin Michels, said:

“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. It may be advisable for manufacturers to consider eliminating BPA from can linings.”

Funding: the Allen Foundation and the Environmental Epidemiology from the National Institute of Environmental Health Sciences both provided grants to pay for this study.

Written by Christian Nordqvist