Study of Baby Teeth Links Autism and Exposure to Heavy Metals Such as Lead
Recent research has revealed that autism is linked to new onset genetic mutations (called ‘de novo’ mutations) that occur during early fetal development. A new study suggests that levels of heavy metals such as lead and zinc (but not mercury) may affect the likelihood that these mutations will occur.
The 2017 study by Manish Arora and colleagues in the journal Nature Communications included twins with and without autism, particularly twin pairs in which one twin had autism and the other did not. An international team of scientists collected naturally shed baby teeth from the twins. The researchers then used lasers to extract specific layers of dentine, the hard substance beneath tooth enamel, which correspond to different developmental periods, including before birth and in early childhood. The researchers then analyzed these dentine samples to determine the children’s uptake of various heavy metals in early life.
The analysis showed that children with autism had higher levels of lead (a neurotoxin) throughout development, but particularly right after birth. Children with autism also had lower uptake of manganese, an essential nutrient. Compared to children without autism, children with autism had lower zinc levels in utero, but higher zinc levels after birth. Zinc is another essential nutrient. Lead and manganese levels were also linked to autism severity.
The method of analyzing teeth allows researchers to look back in time and measure what children were exposed to years earlier. This may help identify environmental factors that contribute to autism spectrum disorders.
