Vitamin B12 FORM – Cyanocobalamin safe? Methylcobalamin adequate? (What I recommend)

January 8, 2020 0 By Ewald Bahringer


We finished off our vitamin B12 discussion
last time with various dosing strategies, including the potential of regularly eating
fortified foods as a possible means of getting enough B12. I mentioned that unlike methylcobalamin, cyanocobalamin
is permitted to be used to fortify foods, and is the form that all the numbers I discussed
in that video apply to for supplementation since it is the best-studied and known to
work. So what’s the deal with all these other forms? Why do they exist at all? And why do some people recommend against taking
cyanocobalamin? There are two main reasons that people recommend
against this form of the vitamin: It’s cyanide content, and the fact that it is not a co-enzyme
form of the vitamin and hence is not a so-called “natural” form. I’m going to argue why there is no need to
be concerned about either of these factors. If you take methylcobalamin, make sure you
watch until the end as I’ll also be touching on how this form of the vitamin may not provide
full nutritional adequacy. First of all, let’s take a quick look at how
vitamin B12 is actually manufactured to inform the rest of our discussion. The cobalamin molecule is far too complex
to be synthesised by chemical methods and all B12 is produced by bacterial metabolism. This notion of “synthetic” and “natural” B12
is a myth – no B12 is synthetic, it is all made by micro-organisms. The four forms of B12 all differ simply by
the moiety bonded to the cobalt atom of the molecule. Bacteria produce all of adenosyl-, methyl-
and hydroxocobalamin, and we intentionally replace these moieties with a cyano group
as part of the extraction process to produce cyanocobalamin, valued for it’s stability
and shelf-life in supplements and foods. But is this added cyano group, a well-known
posion, a concern? The chemically simple cyano group is commonly
found in nature including in many foods and especially certain seeds, so it is unsurprising
that we have biological mechanisms to detoxify small amounts. Indeed, the moiety is found in various molecules
that are important in our own normal functioning. Like with other chemicals, it is the dose
that makes the poison – cyanide only becomes toxic once these mechanisms are overwhelmed. So what is the toxic dose of cyanide? The lowest recorded lethal single dose of
cyanide in humans in .56 mg/kg, or around 40 mg or 40000 μg for a 70 kg person. A common dose of cyanocobalamin is 1000 μg,
of which around 2% is cyanide by weight. So a single dose of this supplement would
provide 20 μg cyanide not all of which will be absorbed, a long way off the worst case
scenario lethal dose of 40000 μg. But we don’t take B12 supplements as a one-off,
we take them regularly and usually every day. What about chronic cyanide poisoning? The WHO has set the provisional maximum tolerable
daily intake of cyanide at 20 μg/kg/day, or around 1400 μg per day for a 70 kg person
– still a long way off the 20 μg found in the supplement. Of course, I recommend you take a lot less
than 1000 μg cyanocobalamin daily, but the reasons for this have nothing to do with cyanide. Check out my last video for more on dose. The other common argument against cyanocobalamin
is that it is not a biologically active co-enzyme form of B12. However, it is common practice for medicinal
preparations, including drugs to be formulated in an inactive form with the intention of
only becoming active on metabolism. There are many reasons for this depending
on the compound, such as improvement of half-life, taste, sensitivity to stomach acid, sequestration
to and use by the relevant tissue, or in the case of cyanocobalamin, stability and absorbability. In fact, even methylcobalamin, though marketed
as a “biologically active form” that does not require conversion, is converted into
an intermediate before being regenerated to methylcobalamin and the other vital form for
humans – adenosylcobalamin. This is an important and relatively unknown
point – methylcobalamin is only one of the two essential biologically active forms of
the vitamin, and there has even been some concern that supplementation with only one
active form may result in inadequacy of the other if this regeneration is insufficient. Given the unjustified condemnation of cyanocobalamin,
methylcobalamin has been more heavily promoted and used recently. This is not recommended given that we need
both forms, so it is suggested we either take both, or much more simply, just take a cyanocobalamin
supplement, which can be converted to both forms. The active forms of B12 are not likely to
be superior to cyanocobalamin and the only way we will know for sure is a randomised
controlled trial comparing the different forms, but until we have that there is nothing wrong
with taking the cheaper and more reliable and stable cyanocobalamin and avoiding the
higher doses we would need to take to ensure adequacy with other forms. To be clear though, the other forms and methods
of administration of cobalamin definitely have their role, such as for pernicious anaemia,
tobacco amblyopia, kidney issues and inborn errors of metabolism including remthylation
disorders, as well as cyanide poisoning, amongst many other indications. The recommendations in this video are for
the general healthy population looking to maintain an adequate status and you should
continue with the form and regimen prescribed by your health care provider. In summary, cyanocobalamin is the form used
to fortify food. Like the three other forms of B12, it is made
by bacteria but has a cyano group added. The amount of cyanide it provides is physiologically
insignificant. The fact that it is not a biologically active
form may actually be an advantage by being more easily converted to both active forms. The other forms play a role in certain conditions,
and the bottom line is to follow the regimen prescribed by your health care provider. Thanks for watching, and I hope this video
has given you a better understanding of the different forms of B12. Be sure to share this video with anyone you
know that might be uninformed on this topic. If there was something that wasn’t clear from
the video, feel free to let me know in the comments and I’ll get back to you. Give us a thumbs-up if you found the video
informative and subscribe if you haven’t already so you don’t miss the next one. That’s it for now though guys, talk to ye
soon. Sláinte!