Oh my, there’s cyanide in B12 supplements. Really. | Science and Society Office

There are many things to worry about in life, but cyanide in vitamin B12 supplements is not one of them. Why am I talking about it? Because of a video circulating about “the toxic ingredient in your child’s vitamins”. In the video, a man says he finds it “hard to believe that we are allowed to make vitamins from hydrogen cyanide in this country, but we are.” That man turns out to be Gary Brecka, who calls himself a “human biologist,” whatever that means, based on a BS in human biology from the National College of Chiropractic. Not exactly Harvard.

Yes, there is indeed cyanide in B12 supplements, but the fear of it is complete nonsense. Vitamin B12 is synthesized by bacteria that inhabit the intestines of animals and is present in foods of animal origin. These bacteria are not found in fruits, grains or vegetables, which is why vegetarians and vegans are generally advised to take a supplement. Vitamin B12, which the body needs for various tasks ranging from red blood cell production and DNA synthesis to proper nerve function, is actually not a single compound. The term can refer to any of four very closely related compounds, each of which has vitamin activity. They share the common characteristic of having a cobalt atom in the center of the molecule, but differ in the substituents attached to this atom. This does not affect their biological activity.

None of these “vitamers,” as they are called, can be synthesized from single molecules in the lab, so supplements must be produced by fermentation using the same bacteria that make B12 in animals. Fermentation yields adenosylcobalamin and methylcobalamin, but the problem here is that these tend to degrade when formulated into supplements. However, treatment with potassium cyanide (not hydrogen cyanide as shown in the video) converts them to cyanocobalamin which is very stable. Once ingested, cyanocobalamin is converted back to the original adenosylcobalamin and methylcobalamin, releasing the cyanide. This is where the fear comes from.

Vitamin B12 doses are measured in micrograms, or millionths of a gram. The recommended daily intake is 2 to 3 micrograms, but supplements can contain up to a few thousand because B12 is poorly absorbed from the gut. Even at the highest doses, the amount of cyanide released is around 20 to 40 micrograms, which is far below the amount of naturally occurring cyanide one might be exposed to by consuming flax seeds, milk unpasteurized almonds, fresh apple juice or apricots.

The oral dose of cyanide below which there is no risk has been determined at 50 micrograms per kg of body weight. This means that a child weighing 15 kg who receives a gigantic daily dose of 1000 micrograms of B12, would ingest even less than 3% of this safe amount! There is simply no problem here. How about people who are drawn to smoothies made with raw almonds or flax seeds, which contain the highest doses of cyanide one could reasonably be exposed to? A 70 kg adult would have to consume 16 normal-sized smoothies in less than two hours to be poisoned with cyanide! A child should drink about three. This is of course completely unrealistic. But what about someone who drinks a smoothie every day that contains as much cyanide as a smoothie can hold, or about 220 micrograms per serving? Always less than 6% of the maximum safe dose!

At the end of the line ? There’s no reason to be concerned about cyanide in vitamin B12 supplements, but there is cause for concern about so-called pseudo-experts with a sketchy understanding of the science alarming the public, usually in plain sight monetary gain in one way or another.


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