For the first time, scientists have described a biochemical mechanism linking attention deficit hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) with the common but problematic compound Bisphenol A (BPA), which can leach into food and water from food and drink packaging.
Researchers at Rowan-Virtua School of Osteopathic Medicine and Rutgers New Jersey Medical School have built on previous studies that have looked at ADHD and BPA exposure and found how those with neurodevelopmental disorders have a much harder time eliminating BPA from the body.
“[This is] the first hard biochemical evidence that the linkage is between BPA and the development of autism or ADHD,” said lead author T. Peter Stein, a Rowan-Virtua professor of surgery. “We were surprised to find that ADHD shows the same defect in BPA detoxification.”
In 2016, US researchers found that kids with ADHD had a significantly higher concentration of urinary BPA. Two years later, a large Chinese study supported this, finding that neurodivergent schoolkids had much higher concentrations of both urinary BPA and 8-hydroxy-2'-deoxyguanosine (8-OHdG, a biomarker of oxidative DNA damage).
Until now, there has been little data on the metabolic processes that underpin BPA exposure and neurodevelopmental diseases in humans.
BPA, an industrial chemical compound that hardens plastic, has been used in food packaging since the 1960s. It can be found in a wide range of common products, including polycarbonate drink bottles and food packaging and containers. Earlier this year, the US Food and Drug Administration backed its previous stance on the use of the chemical in consumer items, saying that "BPA is safe at the current levels occurring in foods.”
BPA is also an endocrine disruptor that can interfere with the body’s natural hormones, affecting cellular responses and important endocrine pathways. Recent studies have shown how extended exposure to BPA can interfere with dopamine transmission, which is a key area of dysregulation in ADHD brains.
Stein and team were looking at the process of glucuronidation in children: 66 with ASD, 44 with ADHD and 37 with no neurodevelopmental issues. Glucuronidation is a key process in the liver that adds a sugar molecule to toxins to make it more water soluble and therefore able to be expelled from the body more quickly. While this process varies between people, an inability to quickly process BPA leaves the body’s tissues vulnerable to exposure to the toxin for longer.
What they found was that the children with ADHD were around 17% less able to add the sugar molecule for efficient glucuronidation, compared to the control group. The process was around 10% poorer for those with ASD.
Clearance of BPA is a “major pathway, otherwise it would not have been so readily detectable in a study of moderate size,” said Stein.
Both ASD and ADHD are complex, multifactorial neurodevelopmental disorders that can’t be attributed to one source. However, little is known about just how the interplay between environmental factors and genes contribute to the conditions.
The team also points out that not every child with ADHD or ASD has the inability to properly process BPA, and there’s little research into older children or adults with these neurodevelopmental conditions.
BPA has already been linked to cognitive impairment, reproductive issues, cancer, and type 2 diabetes. And recent studies have suggested that consumers should not consider its 'alternative', bisphenol S, to be a healthier option.
The study was published in the journal PLoS ONE.
Source: Rowan University