Is Cyanocobalamin just as good as Methylcobalamin and Adenosylcobalamin? How about oral B12?

 

1) 20 mcg of systemically-absorbed B12 is NOTHING compared to what an injection or a transdermal application provide. For early stages of B12 deficiency, 20 mcg may lead to a "quick" repletion, i.e. liver stores restocked within 6 months (liver stores ~3 mg). If you are showing signs of B12 deficiency or plasma levels have begun to drop, your liver stores are compromised, and this takes a long time to replete if only absorbing 20 mcg per day.

 

2) Orally absorbed B12 results in a short window of plasma elevation. This means your tissues have about 2-3 hours to take whatever B12 they need. Injections (especially subcutaneous) and transdermal allow for slow release, extending the cellular availability window by up to 12-fold longer. This is a major advantage to quickly repleting tissue stores and fulfilling cellular demand.

 

3) Though 20 mcg might sound like a lot compared to the RDA, it fails to consider what happens when tissues become depleted and are dependent upon capacity-limited active transport. That 20 mcg is distributed across the entire body, and the brain and nervous system then only have 2-3 hours to obtain B12. Furthermore, the brain stores a small, functional amount of B12 (much less than the liver but not clearly defined), so a B12 deficiency will very quickly impact neurological function. Providing a continuous delivery window for the brain and nervous system would provide a clear advantage over the short delivery window and very modest absorption of oral B12.

 

4) Cyanocobalamin is junk. One of the major benefits of B12 injections and transdermal B12 is a pharmacological effect that is completely separate from its cofactor functions. It neutralizes cyanide and excess hydrogen sulfide (these two have been proven) thus removing a major inhibitor of respiratory chain complex IV. This effect is nil with nutritional doses of B12 and is only measurable when the concentration is of supraphysiological levels. Adenosylcobalamin is not the only reason B12 injections and transdermal B12 have a major positive effect on mitochondrial function - this neutralization of cyanide and hydrogen sulfide in the electron transport chain also improve mitochondrial function in a big way. Cyanocobalamin is not capable of neutralizing cyanide, as it releases a cyanide molecule during lysosomal processing.  The best that cyanocobalamin can do is have no net effect on cyanide in the body - but assuming this scenario also means it would contribute nothing to B12 supply, as the molecule cannot be used in its cofactor functions if it is used to bind cyanide.  At worst, high-dose cyanocobalamin contributes to the body's toxic load of cyanide.

 

5) Finally, to obtain 20 mcg of vitamin B12 every 2-3 hours (let's use 3 hours for charitable math), you would have to take 1000-2000 mcg of vitamin B12 orally 8 times per day, waking up during the night twice to do so (perhaps three times for a child). To obtain the same total B12 exposure by injection (or completely absorbed transdermal B12), one would only need to supply 160 mcg every day - that is a fraction of a drop of either methylcobalamin solution or transdermal product.