Canned food, in most cases, has way too much salt—enough to send any healthy person's blood pressure through the roof. But it may not be the heavy salt content that makes canned food bad for your heart. The can's lining contains a chemical that a new study has linked to widespread kidney problems and cardiovascular disease.
The chemical in question, bisphenol A (BPA), interferes with the way your body produces and regulates estrogen, testosterone, and other hormones, including insulin, which is why past studies have linked it to breast and prostate cancers and to metabolic diseases like diabetes. The chemical also promotes oxidative stress that can damage tissue, the new study found, predisposing you to heart disease and kidney problems.
The New Scary Threat in Canned Soup
The authors used urine samples from 667 children ages 6 to 19 to compare levels of BPA to levels of a protein called albumin; too much albumin in the urine (albuminuria) indicates kidney problems and is usually a precursor to cardiovascular and chronic kidney diseases. They found that high urinary concentrations of BPA went hand in hand with high levels of albumin and the connection was more pronounced in overweight children.
Albumin normally doesn't leak into the urine, because healthy kidney tissue filters it out. But animal studies have shown that BPA can cause oxidative stress to kidney tissues, which may explain what's going on here.
But it's really a sign of damage to the entire cardiovascular system that the study's authors are worried about. "The kidney is like the canary in the coal mine," says study coauthor Howard Trachtman, MD, professor of clinical pediatrics at New York University School of Medicine and NYU Langone Medical Center. "So if BPA is doing something to the kidney, it's possible that it's having an effect someplace else."
In this case, early-life damage to the kidneys could lead to these children developing heart problems later in life. Low levels of albumin in the urine are associated with cardiovascular disease, says the study's other coauthor, Leonardo Trasande, MD, MPP, associate professor of pediatrics and environmental medicine at New York University School of Medicine, and they're a biomarker for endothelial dysfunction, a condition in which the lining of your blood vessels—the endothelium—doesn't dilate properly, upping your risk for everything from strokes to diabetes to Alzheimer's disease. Plus, previous studies by Dr. Trasande and other researchers have already shown that BPA is associated with an increased risk of obesity.
"Diet and physical activity still are the major risk factors for obesity and cardiovascular disease," Dr. Trasande says, "but this study adds to the evidence that environmental chemicals are independent contributors."
And although this was an association study that can't prove cause and effect, it also adds further concerns about use of BPA in canned foods, he says. Diet is largely believed to be our number one exposure source for this chemical, since it's used in the linings of food cans, on the undersides of glass jar lids, and inside aluminum drink cans. "Reducing the number of aluminum cans in your diet can't hurt," he adds.
Canned-food companies are actively seeking out replacements—Campbell's Soup, ConAgra, General Mills, and Heinz have all announced they're switching to BPA alternatives—but a recent study in the journal Environmental Health Perspectives found that the most common BPA replacement was no safer than BPA.
The BPA Replacement You Cannot Trust
Avoiding canned goods is still your best bet in keeping BPA out of your diet. Stick with fresh produce and buy products in cartons and glass jars instead. For the latter, discard any food that stuck to the underside of the BPA-coated lid. And avoid unnecessary cash-register receipts (receipt papers have BPA-based coatings to aid in printing).