In a simple but elegant experiment, researchers at Harvard University demonstrated recently that a potential endocrine disruptor called Bisphenol A (BPA) is present in significant amounts in canned foods (or at least in one brand of canned soup). The researchers employed a randomized, single-blinded, 2x2 crossover design. From a group of volunteers they randomly assigned half of the members to consume 12 ounces of canned Progresso brand vegetarian soup each day for five days. The other half of the group consumed freshly made vegetarian soup for the same five days. Subjects were free to eat whatever else they wished. At the end of the five days they measured urinary BPA levels. Then after a two-day washout period they reversed the soup diets of the members of the group, again measuring BPA levels after five days. Thus the study design gave them paired data, “canned soup” versus “fresh soup”, for each member of the group.
The results surprised even the researchers. After just five days of consuming the canned soup, the urinary concentrations of BPA were over 10 times higher than when the same individuals consumed fresh soup.
BPA is used in the manufacture of polycarbonate plastics. It is found in hard plastic water bottles and in the epoxy resin used to coat the inside of food cans to prevent the cans from corroding. BPA is detectable of in the urine of 92% of all people over six years of age, according to the 2009-2010 National Health and Nutrition Examination Survey. It’s not uncommon to find BPA in humans, in other words.
We don’t know yet whether BPA is safe at the levels being found in humans, and perhaps more importantly, what its effects might be in children. So what should we do - ban it from food and beverage containers now, or wait and see?
REFERENCE: Carwile, J.L et al. Canned Soup Consumption and Urinary Bisphenol A: A Randomized Crossover Trial. JAMA 306:2218-2220, Nov. 23/30, 2011.
(Sorry; this paper is not available free online. Check your school’s library.)