The underlying causes of autism spectrum disorder (ASD) are still up for debate, but new research on diet suggests that increased heavy metal intake, such as lead exposure, and decreased manganese and zinc during late pregnancy, are both associated with a greater risk that a child will be born with ASD.

The study, published online in Nature Communications, also found that the amount of metal exposure after birth helped predict the severity of the child’s autism later in life.

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"Our data shows a potential pathway for interplay between genes and the environment," said study researcher Abraham Reichenberg, in a statement. “Our findings underscore the importance of a collaborative effort between geneticists and environmental researchers for future investigations into the relationship between metal exposure and ASD to help us uncover the root causes of autism, and support the development of effective interventions and therapies."

For their research, the team from Mount Sinai Hospital/School of Medicine looked at toxin and nutrient levels in the teeth of young twins. These twins either were a pair of normally developed children, or a pair where one twin was diagnosed with ASD while the other was not. Both nutrients and toxins that the children were exposed to left an “imprint” on their baby teeth, leaving a chronological list of their environmental and nutritional exposures. The team used this list to compare which nutrients and toxins were more and/or less abundant in twins with ASD as opposed to those without the condition.

According to WebMD, manganese is a mineral found in foods such as nuts, legumes, seeds, tea, whole grains, and leafy green vegetables. It is considered an essential nutrient, because the body requires it to function properly and helps with building strong bones. Zinc is also an essential vitamin linked to proper cell division. Zinc is also found in high amounts in nuts, LiveStrong reported.

Diets low in zinc and manganese are already known to lead to poor growth and development in babies and children, LiveStrong reported, as well as reproductive problems, poor wound healing, low energy, and weight loss in adults.

This study doesn't prove what causes ASD, but it may lead researchers on the right path to eventually uncover the root cause. The team plans to conduct additional research into whether it was differences in the amounts of certain metals and nutrients in the children or differences in their genetics that lead to discrepancies in ASD prevalence.

Source: Arora M, Reichenberg A, Willfors C, et al. Fetal and postnatal metal dysregulation in autism. Nature Communications . 2017

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