A reason to avoid Cyanocobalamin B12

[G2G2]

greenmedinfo.com/blog/99-vi...? The methyl form is safe.

[helvella Administrator Thyroid UK]

I am not impressed by the numbers quoted:

Cyanide in non-vitamin form, of course, is extremely toxic and a poster child of sorts, among dangerous substances. It only takes 6.44 mg per kilogram, or 1.61 mg to kill 50% of your average-sized (500 gram) rats through the oral route of exposure.

Bearing in mind that we are probably doing quite well if we absorb 10 micrograms of B12 (whichever form) from an oral dose. (It is only what we absorb that can be toxic inside our bodies.) Which is about 1/1600 of the 1.61 mg mentioned. The cyanide group is only a tiny fraction of the total mass of cyanocobalamin (about 1.92%). Which works out around 0.19 micrograms of 10 micrograms. We are hugely larger than a rat - of the order of a hundred times the weight.

Yes - I agree that cyanocobalamin seems a less desirable way of getting our B12 by a small margin. (By a larger margin in those who have issues such as Leber's hereditary optic neuropathy or, perhaps, are exposed to higher levels of cyanide.) But Hydroxocobalamin would be my default choice as it is considerably more stable than Methylcobalamin.

(Have not verified the figure, but a single apple seed might contain 1.92 micrograms of cyanide! Most of which will usually pass through without being absorbed.)

[G2G2 in reply to helvella]

Yours are excellent points.

[000ggg in reply to helvella]

When take b12 I take methylcobalamin. It has a dramatic affect. Goes quite high.. it has been jumping around a lot the past three or four years sometimes even without supplementation as far as I recall. It has gone as high as 2400 and now it is back to about 240 on my last test I think. I don’t think I supplemented at all the last time it spiked I think it went to 1000 maybe. Now it has dropped to 240 or so for no reason.