June 2, 2017

Baby Teeth Link Autism, Heavy Metals

BETHESDA, Md -- June 2, 2017 -- Baby teeth from children with autism contain more toxic lead and less of the essential nutrients zinc and manganese, compared with teeth from children without autism, according to a study published in the journal Nature Communications.

Researchers studied twins to control genetic influences and focus on possible environmental contributors to the disease. The findings suggest that differences in early-life exposure to metals, or more importantly how a child’s body processes them, may affect the risk of autism.

The differences in metal uptake between children with and without autism were especially notable during the months just before and after the children were born. Researchers determined this by using lasers to map the growth rings in baby teeth generated during different developmental periods.

The researchers observed higher levels of lead in children with autism throughout development, with the greatest disparity observed during the period following birth. They also observed lower uptake of manganese in children with autism, both before and after birth. The pattern was more complex for zinc. Children with autism had lower zinc levels earlier in the womb, but these levels then increased after birth, compared to children without autism.

The researchers note that replication in larger studies is needed to confirm the connection between metal uptake and autism.

“We think autism begins very early, most likely in the womb, and research suggests that our environment can increase a child’s risk,” said Cindy Lawler, PhD, National Institute of Environmental Health Sciences (NIEHS), part of the National Institutes of Health (NIH), Bethesda, Maryland. “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. With baby teeth, we can actually do that.”

Patterns of metal uptake were compared using teeth from 32 pairs of twins and 12 individual twins. The researchers compared patterns in twins where only 1 had autism, as well as in twins where both or neither had autism. Smaller differences in the patterns of metal uptake occurred when both twins had autism. Larger differences occurred in twins where only one sibling had autism.

The findings build on prior research showing that exposure to toxic metals, such as lead, and deficiencies of essential nutrients, like manganese, may harm brain development while in the womb or during early childhood. Although manganese is an essential nutrient, it can also be toxic at high doses. Exposure to both lead and high levels of manganese has been associated with autism traits and severity.

The study was led by Manish Arora, PhD, Icahn School of Medicine at Mount Sinai, New York, New York. With support from the NIEHS, Arora and colleagues had previously developed a method that used naturally shed baby teeth to measure children’s exposure to lead and other metals while in the womb and during early childhood. The researchers use lasers to extract precise layers of dentine for metal analysis. The team previously showed that the amount of lead in different layers of dentine corresponds to lead exposure during different developmental periods.

“A lot of studies have compared current lead levels in kids that are already diagnosed,” said Dr. Lawler. “Being able to measure something the children were exposed to long before diagnosis is a major advantage.”

The method of using baby teeth to measure past exposure to metals also holds promise for other disorders, such as attention-deficit hyperactivity disorder.

“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,” said David Balshaw, PhD, NIEHS Exposure, Response, and Technology Branch.

SOURCE: National Institutes of Health
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