I see that cyanocobalamin is not naturally occurring, and is synthesized in vivo to methylcobalamin. As part of the synthetic pathway, cyanide is broken off. All opinions I can find are that this isn't a problem as cyanide is naturally occurring in many foods anyway, and is safely detoxified via the the Rhodenase pathway.
However, given its synthetic creation and vast prevalence as the primary B12 source in nearly all supplements, I was curious if any actual studies did exist to rule out potential (albeit minor) long term cyanide toxicity for this synthetic form of B12. I'm unable to find a single study where cyanide toxicity was directly tested for, only studies stating that RDA in excess of 1000 times the daily dosage isn't lethal.
I understand no evidence currently exists for cyanocobalamin toxicity, but this wouldn't be surprising if there aren't any studies done in the first place.
Would anyone be able to reference an actual study that directly measured levels of potential cyanide toxicity for cyanocobalamin in any animal or humans?