Health-conscious people who prefer chemical-free foods—produced without artificial colors, flavors, or preservatives—might be getting unexpected exposure to a potentially harmful chemical if they eat or drink from containers made from or lined with certain plastics. A new study in the Journal of the American Medical Association found that bisphenol A (more commonly known as BPA), a chemical that leaches into foods and drinks from can liners and some plastics, may be linked to increased risk of heart disease and diabetes.

BPA in the modern world

BPA is a chemical compound used to manufacture such widely used materials as polyester, polycarbonate plastics, and epoxy resins. Polyvinylchloride (known as PVC) used in household plumbing, dental sealants, liners for food and beverage cans (especially for acidic foods and drinks like tomatoes and sodas), and most number 7 plastics are made with BPA.

At room temperature, small amounts of BPA slowly leach into food and drinks, but at higher temperatures, leaching can occur as much as 55 times faster. Strong cleaning chemicals can damage plastic surfaces and contribute to increased leaching of BPA.

Concerns about the health effects of long-term BPA exposure have primarily focused on its ability to act like estrogen in the body, but researchers have suggested that it may act in other harmful ways as well.

Measuring the effects of BPA in humans

The new study included data from a subset of 1,455 adults participating in the National Health and Nutrition Examination Survey (NHANES) 2003–2004. The people in the study had urine tests to measure BPA levels and blood tests to measure some disease risks, and answered questions about their health status.

People with the highest BPA levels were almost three times more likely to report being diagnosed with cardiovascular disease, including angina, coronary artery disease, and heart attack, than people with the lowest BPA levels. Having the highest BPA levels was also associated with a 2.43-fold increase in risk of type 2 diabetes. Obese people’s urine BPA levels were 1.8 times higher than those of normal-weight people. In addition, higher BPA levels were associated with abnormalities of blood tests that indicate liver cell damage.

“We found that higher BPA concentrations [in urine] were associated with diagnoses of heart disease and diabetes. We also found associations between high concentrations and clinically abnormal concentrations of three liver enzymes,” the researchers said in summary. “Importantly, we observed no associations with the other common conditions examined.” The other conditions examined were cancer, arthritis, respiratory disease, stroke, and thyroid disease.

Reduce your exposure

The authors of this study used models to estimate daily BPA intake based on the urine concentrations measured and found that average intake was far below the safety guidelines set by the US Environmental Protection Agency. If future research confirms a link between this level of intake and risk of heart disease and diabetes, it will be important to reconsider recommendations about what level of BPA intake is safe.

In 2003–2004, the US Centers for Disease Control found that 93% of adults and children had detectable levels of BPA in their urine. As a result of mounting public pressure, some manufacturers have stopped using BPA in their production of baby bottles and water bottles, and some canners have stopped using epoxy resins to line cans for non-acidic foods. Last week, Canada became the first country to ban the use of BPA in the manufacturing of baby bottles.

You can take steps to reduce your exposure to BPA:

• Don’t use number 7 plastic baby bottles. Warm infant formula more safely in glass bottles and plastic bottles labeled “BPA-free” or made from number 2 or 5 plastics.

• Only fresh cold water should be drunk from number 7 plastic bottles. Better yet, get a stainless steel water bottle, or one made with number 2 plastic.

• Avoid heating food in microwavable plastic, which is likely to be made with number 7 plastics.

• Emphasize fresh and frozen foods to limit canned food and drink consumption.

(JAMA 2008;300:1303–10)

Maureen Williams, ND