With commentary by Teresa Attina, MD, PhD, MPH, a staff scientist at NYU Langone Medical Center
Teens who eat food that's been packaged in plastic wrap or stored in plastic food containers may be at higher risk of developing type 2 diabetes, according to new research published online in the May 2015 Journal of Clinical Endocrinology and Metabolism.
The study found that exposure to the chemicals used to make the plastics in these products more flexible may decrease how well the body uses insulin to control blood sugar, increasing the risk of diabetes, says lead researcher Teresa Attina, MD, PhD, MPH, a staff scientist at NYU Langone Medical Center. Exposure to the chemicals may also boost blood pressure, she found in her research. .
"We found that two chemicals widely used as plasticizers—the kind of thing you wrap your food in or your sandwich with—seem to have a toxic effect themselves," she says. Ironically, the two chemicals were developed as safer substitutes for another chemical known to have toxic effects, explains Dr. Attina.
To look at the effects of the chemicals on insulin, Dr. Attina and her team evaluated blood and urine samples from 356 teens, ages 12 to 19. They were participants in the long-running National Heart and Nutrition Examination Survey (NHANES). The researchers analyzed the samples for metabolites of the two ''replacement'' chemicals, DINP (di-isononyl phthalate) and DIDP (di-isodecyl phthalate). Those two chemicals are used to replace DEHP (di-2-ethylhexylphthalate) not only in plastic wrap but in processed food containers, soap, and cosmetics. DEHP has been linked with adverse health risks. Attina and her team had already reported that DEHP is linked with insulin resistance, or a decreased ability to use insulin effectively.
The teens with the highest levels of DINP were more likely to have insulin resistance, Dr. Attina found. "The more insulin resistance, the more likely they are to develop diabetes," she says. She also confirmed the link, already discovered, between DEHP exposure and insulin resistance.DIDP exposure wasn't linked to insulin problems, but did boost blood pressure, she found.
The link between high levels of the chemical DINP in the blood and urine with higher insulin resistance held, says Dr. Attina, even after she took into account other factors that boost the risk of getting type 2 diabetes, such as being obese.
One of three teens with the highest DINP levels, for instance, had the highest insulin resistance, while only one in four of those with the lowest levels did, the researchers found. In the U.S., more than 29 million people have diabetes, and type 2 diabetes is on the rise among youth. In type 2, the body does not use insulin effectively. Besides excess weight, it's driven by inactivity.
Because of the study design, the researchers cannot say that exposure to the chemical causes the insulin resistance, Attina says, but the link or association is strong. Exposures to the chemicals might be especially hazardous, she says, in teens who already have some risk factors, such as being overweight or eating a poor diet.
"All these things add up and can contribute overall to the risk of getting diabetes," she says.
Luis Gonzalez-Mendoza, MD, director of pediatric endocrinology at Nicklaus Children's Hospital in Miami, agrees that parents should be concerned about the possible cumulative effects of risk factors. "The biggest driver of insulin resistance is excess weight," he says. However, he adds, ''on top of our kids getting overweight, being exposed to this on top of that could have a cumulative effect."
The study only looked at teens, so the researchers cannot say from the study if the chemicals might boost adult risk, too. “With respect to adults, they are also exposed to phthalates, but most of the available studies focus on kids (and pregnant women), as early life exposure seems to be the most detrimental in terms of health consequences,” says Dr. Attina.
Dr. Attina says it's fairly easy to avoid exposure to these chemicals:
Dr. Gonzalez-Mendoza agrees that this is good advice: "Some pediatricians I know already suggest those steps," he says. While the new studies looked just at the effect of the chemicals on insulin and blood pressure, he says plastic exposure may be linked with other health problems as well. These may include obesity and the timing of puberty.