Does soy-based infant formula cause ADHD? Update and public policy considerations.

An earlier article hypothesized a relationship between soy-based infant formulas, manganese (Mn) neurotoxicity and symptoms of ADHD. In this update, more recent literature on ADHD, Mn and Mn neurotoxicity is reviewed, as well as the risks of Mn toxicity that may accompany ingestion of soy-based infant formula. The results of several critical studies are described, including rodent and primate models that demonstrate an association between ingestion of relatively high levels of Mn and: overactivity, disinhibition and inattention; stereotypes and disturbances of social relatedness; and alterations of dopamine D1 and D2 receptors and dopamine transporter in critical brain regions. Similar deficits have been shown in children with ADHD. In addition, ADHD-like symptoms of behavioral disinhibition were found to be correlated with Mn content in tooth enamel, apparently deposited at or before the fifth gestational month. The results are discussed in terms of their weight as a risk factor in ADHD, vis-à-vis compelling evidence of genetic, epigenetic and other environmental risk factors associated with the disorder, as well as the appropriateness of additional public policy decisions regarding the safety of soy formula.