In order to improve autism treatment or prevent the disease, it’s imperative to understand what causes it. New research from the National Institute of Environmental Health Sciences found that the baby teeth of children with autism carry more dangerous lead and less zinc and manganese, which are important minerals. To rule out genetic and environmental influences, the investigators used sets of twins in their work. These findings, which were reported in Nature Communications and are outlined in the following video, suggest that exposure to metals and how a body deals with it could be affecting the development of autism.
There are growth rings in baby teeth, and the scientists used lasers to follow them, mapping throughout various developmental stages. They determined that the differences in the uptake of metals was pronounced right before and after birth. Throughout development, there were higher lead levels in autistic children, although the greatest disparity was found after birth. For zinc, it was more complicated. Compared to non-autistic children, autistic children had lower levels of zinc before birth, while the levels normalized after birth.
“We think autism begins very early, most likely in the womb, and research suggests that our environment can increase a child’s risk. But by the time children are diagnosed at age 3 or 4, it’s hard to go back and know what the moms were exposed to,” said Cindy Lawler, Ph.D., head of the NIEHS Genes, Environment, and Health Branch. “With baby teeth, we can actually do that.”
The research was conducted with the teeth of 12 individual twins and 32 twin pairs. There were comparisons of twins with only one case of autism, with both twins affected, and with neither affected by autism. Greater differences were seen in metal uptake patterns in the case of twins with only one autistic child. The small sample size will recently require confirmation with more participants, something the researchers noted.
Previous work has shown that deficiencies of important nutrients or exposure to lead and other toxic metals can harm development of the brain in utero or in early childhood. Manganese appears to be both harmful at levels that are too high or too low, increasing risk of autism and the severity of it.
Manish Arora, Ph.D., an environmental scientist and dentist at the Icahn School of Medicine at Mount Sinai in New York led the work, and has created a way to analyze metal exposure through baby teeth. Arora noted that genes and the environment probably both influence autism development, but it’s been a challenge to figure out what in the environment increases the risk.
“What is needed is a window into our fetal life,” he explained. “Unlike genes, our environment is constantly changing, and our body’s response to environmental stressors not only depends on just how much we were exposed to, but at what age we experienced that exposure.”
“A lot of studies have compared current lead levels in kids that are already diagnosed,” said Lawler. “Being able to measure something the children were exposed to long before diagnosis is a major advantage.”
It may be possible to use baby teeth for researching other developmental disorders. “There is growing excitement about the potential of baby teeth as a rich record of a child’s early life exposure to both helpful and harmful factors in the environment,” commented David Balshaw, Ph.D., head of the NIEHS Exposure, Response, and Technology Branch.