What Can Baby Teeth Tell Us about Autism and Heavy Metals?
Autism is a complex, diverse developmental disorder, and there is still so much we don’t know about it. But in recent years, there have been incredible advancements. Consider some of the wide-ranging potential causes and risk factors that have been identified: Research has linked autism spectrum disorder (ASD) to various biological, environmental, and genetic elements, as well as to prenatal exposure including certain prescription drugs.
Now researchers from the Institute for Exposomic Research at the Icahn School of Medicine at Mount Sinai have unveiled a new milestone: They discovered a way to predict ASD by looking at baby teeth. The teeth show how babies and children metabolize metals, which are essential for neurodevelopment. And disruptions in these biological processes have been linked to ASD.
To detect the presence of metals, researchers studied the zinc-copper cycles—the rhythmic patterns of these metals in the body that regulate metal metabolism—of shed baby teeth. During fetal development, babies’ teeth form new layers, which can show what metals the babies were exposed to during development. “Teeth are like biological hard drives that take a snapshot of what’s happening in the body every day,” says Dr. Christine Austin, an analytical chemist and a postdoctoral fellow in the Department of Environmental Medicine and Public Health at the Icahn School of Medicine. “We can use teeth to go back in time to measure early-life exposures to metals.”
The analysis shows that the zinc and copper metabolic rhythms were disrupted in the children with ASD, says Austin, who led the baby teeth analysis in the study, along with Dr. Manish Arora, a professor of dentistry and environmental medicine and public health at the Icahn School of Medicine.
Austin and Manish’s findings could have far-reaching implications for how early we detect ASD and offer therapies to children with ASD. Further, it could change how we detect and treat other neurological disorders in kids and even neurodegenerative conditions that manifest later in life. Their research is also fascinating for another reason: what it might tell us about exposure to heavy metals and how the body metabolizes them.
Q&A with Christine Austin, Ph.D., and Manish Arora, Ph.D.
Austin: Environmental factors influence ASD risk, but these factors are understudied. This is a missed opportunity because, unlike genetics, we can modify our environment to reduce the risk of ASD.
The brain is most vulnerable to environmental exposures early in life—meaning before birth and during early childhood. But studying the role of early-life exposures in ASD is challenging. To do this type of study well, we would typically follow thousands of pregnant women and their children to see who developed ASD. Next, we would find exposures that are linked to the disease. This type of study is expensive and takes years to generate results. To address these issues, we’ve developed a new technology using baby teeth. Teeth are like biological hard drives that take a snapshot of what’s happening in the body every day. We can use teeth to go back in time to measure early-life exposures to metals. This way, we can study children with ASD and children without ASD without having to follow them for years. Then we can identify exposures in teeth that occurred before symptoms of ASD were apparent.
Arora: The method we developed is known as a classifier. We used baby teeth to try to predict which children do and do not have ASD—and we distinguished them with 90 percent accuracy. In ASD teeth, we identified disruptions in zinc-copper cycles from the second trimester of pregnancy through the first year after birth. Kids start losing their baby teeth around six years of age, which is after most children with ASD have shown clinical signs. So this makes baby teeth less useful as a screening tool. However, if we can collect other biological samples around the time of birth and identify the same zinc-copper disruption, we could potentially create a different early-screening tool for ASD. Early detection of ASD could improve outcomes by allowing early introduction of therapies.
There is the potential that our technology could be used to detect other disorders. Currently, we are working on methods to distinguish between ASD and other neurological disorders in children, such as attention deficit hyperactivity disorder (ADHD). We’re also studying neurodegenerative conditions that manifest later in life, such as Lou Gehrig’s disease (ALS).
Austin: Several studies have linked early-life exposure to metals—both high levels of toxic metals and deficiencies of nutritional elements—with symptoms associated with ASD, like intellectual disability, language and attentional problems, and behavioral issues. However, studies looking at the relationship between metals and ASD diagnosis have shown mixed results. Some studies have found links between toxic metals and ASD, while other studies have not. Evidence suggests that metals are absorbed and metabolized differently in children with ASD but a major limitation of these studies is that they are measuring metal levels after diagnosis. This makes it difficult to know whether metal concentrations in these studies are a consequence or a cause of the disease.
Early-life exposure to metals could be an important player in ASD risk. However, our work focuses not only on metal concentrations but also on metabolic cycles and timing of exposure. Importantly, this dysregulation is apparent before diagnosis of ASD.
Arora: Our study shows that, in children who go on to develop ASD, the zinc-copper metabolic cycle is disrupted during early life. Zinc and copper are nutritional elements that are tightly regulated in the body. They also affect the metabolism of other metals. The zinc and copper levels we measured were not high enough to be considered toxic exposures. Rather, the timing and rhythmicity of zinc-copper cycles were altered in children with ASD. It is possible that the disruption of zinc metabolism may increase vulnerability to toxic metals as well.
Austin: Yes, our method can measure multiple metals within a baby tooth. In our study, we also found disruptions of zinc-lead cycles in children with ASD. Currently, we are investigating other toxic or nutritional metals that may be dysregulated in children with ASD.
Arora: There are simple steps any family can take to reduce environmental exposures in the home. Our Mount Sinai Children’s Environmental Health Center and Region 2 Pediatric Environmental Health Specialty Unit has a guide, Ten Tips to Greening Your Family. If you have concerns about possible environmental exposures where children live, learn, eat, sleep, or play, talk to your child’s pediatrician. If you need further assistance from an environmental expert, you can find one through the national Pediatric Environmental Health Specialty Unit.
Austin: We found that zinc-copper cycles in baby teeth distinguish children with ASD from neurotypical children. We hope to refine our classifier and test it using other biological samples available at birth. This would be the first step toward developing an ASD screening tool that could be applied soon after birth. Ideally, this will enable early-intervention strategies.
Dr. Christine Austin received her Ph.D. from the University of Technology, Sydney. She is a postdoctoral fellow in the Department of Environmental Medicine and Public Health at the Icahn School of Medicine at Mount Sinai in New York City. Austin specializes in the development and application of analytical chemistry techniques in studies of children’s environmental health.
Dr. Manish Arora is an environmental epidemiologist and exposure biologist. He is the Edith J. Baerwald Professor and the vice chairman of the Department of Environmental Medicine and Public Health at the Icahn School of Medicine at Mount Sinai in New York City. He received his Ph.D. from the University of Sydney and undertook postgraduate fellowship training at the Harvard School of Public Health. Arora’s research focuses on effects of prenatal and early-childhood chemical exposures on lifelong health trajectories.
The views expressed in this article intend to highlight alternative studies. They are the views of the expert and do not necessarily represent the views of goop. This article is for informational purposes only, even if and to the extent that it features the advice of physicians and medical practitioners. This article is not, nor is it intended to be, a substitute for professional medical advice, diagnosis, or treatment and should never be relied upon for specific medical advice.