But levels of B12 that are too low can be detrimental. "At some point, an extreme decrease in metabolism…is not compatible with cell survival," Deth said. Similarly, lower vitamin B12 levels can have negative consequences for people of younger ages, as the brain is still developing. Deth's group found that the levels of vitamin B12 in the brains of young people with autism and in middle-age people with schizophrenia were about one-third of the levels found in similarly aged people who did not have these neurological conditions.
The people in the study with autism, who were all under age 10, had levels similar to those found in a 57-year-old. It's not clear what these low levels imply, but the uptake of too little B12 might hinder the brain's ability to establish important neural connections between regions, Deth said.