Many companies began phasing out BPA in baby bottles and other plastic food containers in recent years to ease public anxieties, but it is still widely used in the linings of metal cans because it helps prevent corrosion and is resistant to high heat during the sterilization process.
People who ate one serving of canned food daily over the course of five days, the study found, had significantly elevated levels — more than a tenfold increase — of bisphenol-A, or BPA, a substance that lines most food and drink cans.
As part of the study, Dr. Michels and her colleagues recruited a group of 75 staff members and students at the Harvard School of Public Health, split them into two groups, and then followed them for two weeks. During the first week, one group ate a 12-ounce serving of vegetarian soup from a common brand of canned soup every day for five days; the other group, meanwhile, ate 12 ounces of vegetarian soup made from fresh ingredients each day. Then, after a two-day soup-free “wash out” period, the groups switched roles and were followed for five more days. At the end of each five-day period, the subjects provided urine samples.
In general, most studies have found that urinary BPA levels in typical adults average somewhere around 2 micrograms per liter. That was roughly the levels the Harvard researchers found in the subjects after a week of eating the soup made from fresh ingredients. After eating the canned soup, though, their levels rose above 20 micrograms per liter, a 1,221 percent increase.