Children exposed to two chemicals commonly used in food packaging are more likely to be obese or show signs of diabetes precursors than those with lower exposure, new research suggests.
Researchers found urine levels of one type of phthalate, used to soften plastic, were tied to a higher risk of insulin resistance among teenagers. Based on data from the same large nutrition survey, another study group linked bisphenol A, or BPA – used to line aluminium cans – to obesity and larger waists in youth.
According to the Centres for Disease Control and Prevention, about one in six US children and teenagers is now obese. "Clearly unhealthy diet and lack of physical activity are the drivers of this epidemic... but increasingly environmental chemicals are being identified as possible contributors," Dr Leonardo Trasande, a paediatrician from New York University, said. He and his colleagues analyzed data from a nationally-representative health and nutrition survey conducted in 2003 to 2008, which included urine and blood tests for 766 adolescents aged 12 to 19.
They found urinary levels of one particular type of phthalate, known as Di-2-ethylhexylphthalate (DEHP), were closely tied to a teenager's chance of having insulin resistance, a precursor to diabetes. Just under 15% of study participants with the lowest one-third of DEHP levels were insulin resistant, compared to almost 22% of those with the highest levels. DEHP, Trasande said, is often used to soften plastic bottles. It's used in plastic that is printed with the number 3 for recycling.
The researchers said their findings don't prove that eating food packaged with phthalates causes insulin resistance. For example, it's possible children who are already insulin-resistant have unhealthier eating habits and eat and drink more packaged products – thus the higher phthalate levels in their urine.
But Trasande told Reuters Health the chemical may influence how the body secretes insulin in response to sugar. Because of that, he tells parents to avoid buying plastics made with DEHP. "I advise them not to wash plastic containers in the dishwasher," he said. "When the plastic is clearly etched or damaged, it's time to throw it away."
Dr Joyce Lee from the University of Michigan in Ann Arbour and her colleagues used nutrition survey data through 2010 to compare BPA levels in the urine of six- to 18-year-olds with other health measures. In their analysis of 3 370 kids, BPA – an industrial chemical that may mimic oestrogen in the body – was not linked to insulin resistance or blood sugar.
But children with higher BPA levels were more likely to be obese, and tended to have a higher waist circumference-to-height ratio, than those with the lowest levels. A total of 18% of kids in the study were obese, based on CDC growth charts.
Compared to children with the lowest BPA levels, the 25% with the highest levels were twice as likely to meet the cut-off for obesity. The average child had 2.6 nanograms, or 2.6 billionths of a gram, of BPA in every millilitre of urine. The findings are in line with a 2012 study that used some of the same data and also linked BPA in kids' urine to their chance of being overweight or obese, without proving a cause-and-effect relationship.
Variety of chemicals in children's products
"That study adds further concerns to the ongoing use of BPA in food," Trasande said. "There are a variety of chemicals used in children's products, including BPA, as well as other chemicals of less notoriety that our kids are exposed to on a daily basis, for which there are unknown health effects," Lee told Reuters Health in an email.
"Although the evidence about BPA and adverse health effects are not definitive, as a clinician, I do recommend that parents try to avoid BPA-containing plastics when possible to minimise their family's exposure. I also tell them to avoid microwaving food in plastic containers, as this can lead to chemicals leaking into the food," Lee said.
Still, one researcher cautioned that urinary levels of BPA and other chemicals may not say a lot about how much actually gets into children's blood and tissues. "Everybody who does BPA studies uses the urine for a surrogate of exposure.
It's erroneous, because the urine is purely what the person took in that day in BPA," Dr Robert Brent from Alfred I. DuPont Hospital for Children in Wilmington, Delaware, who wrote an editorial accompanying the new studies, said.
"In order to know what exposure is you have to have the blood level of the chemical," he told Reuters Health – as well as how quickly it breaks down in the blood.
Last year the US Food and Drug Administration banned BPA from baby bottles, but said there was not enough evidence for a more widespread ban. The FDA has not placed regulations on phthalates in food products, Trasande's team noted.