Eating canned food every day may raise the levels of the compound bisphenol A (BPA) in a person's urine more than previously suspected, a new study suggests.
People who ate a serving of canned soup every day for five days had BPA levels of 20.8 micrograms per liter of urine, whereas people who instead ate fresh soup had levels of 1.1 micrograms per liter, according to the study. BPA is found in many canned foods — it is a byproduct of the chemicals used to prevent corrosion.
When the researchers looked at the rise in BPA levels seen in the average participant who ate canned soup compared with those who ate fresh soup, they found a 1,221 percent jump.
"To see an increase in this magnitude was quite surprising," said study leader Karin Michels, an associate professor of epidemiology at the Harvard School of Public Health.
The levels of BPA seen in the study participants "are among the most extreme reported in a nonoccupational setting," the researchers wrote in their study. In the general population, levels have been found to be around 1 to 2 micrograms per liter, Michels said.
The study noted that levels higher than 13 micrograms per liter were found in only the top 5 percent of participants in the National Health and Examination Survey, which is an ongoing study conducted by the Centers for Disease Control and Prevention.
"We are concerned about the influence of [hormone-disrupting] chemicals on health in general, and BPA is one of them," Michels told MyHealthNewsDaily.
The study is published online today (Nov. 22) in the Journal of the American Medical Association.
Soup for lunch
The study included 75 people, whose average age was 27. One group of participants ate 12 ounces of fresh soup every day at lunchtime, while the other ate the same amount of canned soup each day. Urine samples were collected from the participants on the fourth and fifth days of the study.
BPA was detected in 77 percent of people who ate the fresh soup, and all of the people who ate the canned soup, according to the study.
Only a few studies had previously looked at BPA levels from eating canned foods, and those relied on asking people how much of the food they usually eat comes from cans, Michels said. The new study was the first in which researchers randomized participants to eat a small serving of canned food or fresh food, and measured the resulting difference in their urine BPA levels, she said.
"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 study researcher Jenny Carwile, a doctoral student at Harvard.
BPA and health
A 2008 study of 1,455 people showed that higher urinary BPA levels were linked with higher risks of developing cardiovascular disease and diabetes, and abnormal concentrations of certain liver enzymes, even after factors such as age, body mass index and smoking were taken into account.
And other studies have linked BPA levels in a woman's urine during her pregnancy to health problems in her child.
It is not known how long the levels of BPA might remain high, according to the study. However, it is also not known whether such a spike, even if it isn't sustained for very long, may affect health, the researchers wrote.
The study was limited in that all of the participants were students or staff at one school, and a single soup brand (Progresso) was tested, but the researchers wrote that they expected the results to apply to canned foods with a similar BPA content.
"Reducing canned food consumption may be a good idea, especially for people consuming foods from cans regularly," Michels said. "Maybe manufacturers can take the step of taking BPA out of the lining of cans — some have already done this, but only a few."
The study was funded by the Allen Foundation, which advocates nutrition research.