April 27, 2019
A variety of common everyday chemicals is adding to the current obesity epidemic among American children, and pediatricians need to educate and advocate against their use, according to Leonardo Trasande, MD, from NYU Langone Health in New York City.
"Synthetic chemical exposure in utero can scramble molecular and hormonal signals that can set children up to develop obesity and cardiovascular risks through a number of mechanisms," Trasande told Medscape Medical News.
The most prominent of these potential mechanisms involves the direct metabolic disruption of several pathways, which "can literally make fat cells bigger or disrupt the function of proteins that protect the heart, for example," he explained.
"There are also sex-hormone effects from synthetic estrogens like bisphenol A [BPA], which can influence children's risk of obesity in a sex-specific way, especially during certain vulnerable windows of development, such as puberty," said Trasande, who discussed the topic at the Pediatric Academic Societies 2019 Meeting in Baltimore.
Categories of Chemicals Implicated
In recent years, three categories of synthetic chemicals have been identified as having the potential to exacerbate childhood obesity through metabolic disruption: bisphenols, phthalates, and per- and polyfluoroalkyl substances (PFSAs).
Among the bisphenols, BPA — an industrial chemical that has been used to make plastics and resins for the past 5 decades and is found in a variety of consumer goods, such as plastic containers that store food and beverages — has been the subject of extensive research.
Some of these studies have demonstrated that BPA can seep from plastic containers into food or beverages, exposing consumers to potential deleterious effects.
BPA can mimic estrogen in the body and potentially change the timing of puberty, decrease fertility, increase body fat, and affect the nervous and immune systems. Nevertheless, the US Food and Drug Administration (FDA) has said that exposure to low levels of BPA is safe.
Phthalates, the group of chemicals used to soften and increase the flexibility of plastic and vinyl, are similarly ubiquitous and found in hundreds of consumer products, from vinyl flooring to detergents, raincoats to shampoos, and plastic wrap to children's toys.
Although various government agencies assert that the health effects from phthalate exposure are not known, Trasande is not so gratuitous in his assessment.
"In particular, phthalates influence the expression of certain receptors, called PPARs," he explained. "These receptors are highly influential in lipid and carbohydrate metabolism."
"Phthalates are also oxidative stressors," he said. "Oxidative stress is a key factor in the development of insulin resistance and another pathway by which these chemicals can induce obesity, diabetes, and cardiovascular risks."
Like bisphenols and phthalates, PFASs — a group of man-made chemicals that includes perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), and GenX chemicals — are found in many everyday household products, most commonly in stain- and water-repellent fabrics and nonstick pots and pans.
And because PFASs have been used in a variety of industries since the 1940s, they are persistent in the environment and the human body, said Trasande.
These chemicals can have deleterious effects in humans, and can even counteract the benefits of a healthy lifestyle, he reported. "In studies of adults, at least, PFASs have been associated with weight regain, even in people who have lost the weight through healthy diet and increased physical activity."
The fact that these chemicals seem to affect weight gain irrespective of positive behavioral changes is perhaps one of the most disturbing aspects of these chemicals, he said.
"There is emerging science that actually minimizes the importance of diet and physical activity in the obesity epidemic," he explained.
Consumers should take safe and simple steps to minimize exposure to these compounds.
An easy way to limit exposure to bisphenols, particularly BPA, is to avoid canned food. And the elimination of highly packaged and processed foods will help reduce phthalate exposure. In addition, use of alternatives to nonstick cookware is a simple way limit exposure to PFASs.
Plastic should never be used in the microwave because microscopic phthalates and other plastic monomers can leech into food, said Trasande. This leeching can also occur when plastics are washed in the dishwasher or with harsh chemicals, so hand-washing is advised.
Pediatricians can serve as vital resources in the fight against chemical exposure. The most obvious way, Trasande pointed out, is as a source of credible information.
"We should be educating families about what they should and shouldn't eat," he explained.
Equally important, but often overlooked, is the role that pediatricians can play in educating decision-makers on the effects of these chemicals and the benefits of regulations that limit exposure.
"In some ways, the responsibility for education about these compounds has fallen to pediatricians," said Sheela Sathyanarayana, MD, from the University of Washington in Seattle, who chaired the session on chemical exposure and obesity.
This is "partially because the public is largely unaware of federal regulations regarding chemicals," she explained, "and the loopholes that exist.
"I think most families get their education about nutrition from their doctors, whether it's adults or children," she told Medscape Medical News.
'Generally Recognized as Safe'
The role pediatricians can play and the call for reforms to the nation's food-additive regulatory process are among the many things discussed in a statement on food additives and child health from the American Academy of Pediatrics (Pediatrics. 2018;142:e20181410), which both Trasande and Sathyanarayana were involved in developing.
The statement also calls for more rigorous and transparent regulations regarding the designation of chemicals as "generally recognized as safe" by the FDA. Specifically, the academy calls for new requirements for the testing of chemicals for toxic effects before they reach the marketplace.
"The 'generally recognized as safe' designation means a chemical doesn't have to go through the typical toxicity testing or regulation that the FDA requires for components of foods," Sathyanarayana explained.
"The burden is on industry to determine that these compounds are safe for human consumption, which leaves many gaps for substances that could be harmful to the general public," she added. "And that's one of the reasons we wrote the statement. Most people don't know there are a lot of things in their foods that do not have to go through the normal regulatory process."
The statement also advocates for the retesting of chemicals already approved.
"The FDA Act was created in 1938, the amendment was in 1968, and it has not been updated since then," Sathyanarayana reported. "Many of the newer processes we have for determining food chemical safety didn't apply to those compounds that were approved a long time ago."
Although it might seem like physicians and consumers are fighting an uphill battle against the constant flow of chemicals into their lives, both Trasande and Sathyanarayana are hopeful that change is possible, and imminent.
Public uproar has been the motivating factor in most instances. "We've seen with BPA-free baby bottles and sippy cups that consumer action can drive the change we seek," said Trasande, whose book — Sicker, Fatter, Poorer — was published earlier this year.
"We've seen levels of bisphenols drop on the order of 50% over the past decade, and the same is true for phthalates," he added.
Trasande and Sathyanarayana have disclosed no relevant financial relationships.