An autism cohort study of cobalt levels following vitamin B12 injections

The effects of methylcobalamin (vitamin B12) injection (75mg kg ) on cobalt levels in autism spectrum disorders (ASDs) and potential toxic effects of cobalt on human neurons were evaluated. A cohort of ASDs (n1⁄4 72) presenting to the Genetic Centers of America were evaluated for the frequency of methylcobalamin injections and cobalt levels using Laboratory Corporation of America (LabCorp) testing. Potential toxic effects of cobalt (cobalt(II) nitrate hexahydrate) to human neurons grown in vitro were evaluated. Methylcobalamin injections significantly increased the mean levels of plasma cobalt (6.83-fold) and urinary cobalt (51-fold) in comparison to unexposed subjects, and significant positive correlations were found between the frequency of methylcobalamin injections and the levels of plasma and urinary cobalt (injections every second day induced cobalt levels in excess of the LabCorp cobalt occupational maximum exposure limits). The LC50 in human neurons following 24 h incubation with cobalt is 559mM. Research must be conducted to determine optimal therapeutic methylcobalamin doses.