What B12 Supplement Should I Take?
I get this question all the time, so I finally decided to write up a blog post to point people to.
Cyanocobalamin is the most common form of B12 supplement and is the form found in fortified foods. It doesn’t occur much in nature, but it is the most stable form of vitamin B12, and the cheapest. It has been the most studied form and has consistently been shown to be effective. Unless there are extenuating circumstances, I recommend that people take cyanocobalamin as their B12 supplement.
Cyanocobalamin contains a molecule of cyanide, but the amount of cyanide in cyanocobalamin supplements is so small as to be physiologically insignificant (more info).
Some people have cyanide metabolism defects, and they should not take cyanocobalamin. If you are asking yourself right now if you might be one of those people, you can assume the chances are close to zero.
People with cyanide poisoning should not take cyanocobalamin. If you have not previously suspected that you might have cyanide poisoning, then you can assume you don’t have it.
People with chronic kidney problems should probably take a non-cyanocobalamin form of B12 (more info).
Finally, cigarette smokers might want to take a non-cyanocobalamin form of vitamin B12 as they can build up cyanide in their system. This is theoretical – I have never come across a vegan cigarette smoker who reported vitamin B12 deficiency based on taking cyanocobalamin and the Institute of Medicine has concluded that “The effect of smoking on the B12 requirement thus appears to be negligible (1).” (More info.)
Methylcobalamin & Adenosylcobalamin
Methylcobalamin is one of the two co-enzyme forms of vitamin B12, the other being adenosylcobalamin (known by many other names, including “dibencozide”). When I first got into the B12 issue, dibencozide was all the rage, now it’s methylcobalamin for some reason. The two forms have different functions in the body and both are necessary (more info).
Methylcobalamin is promoted by some alternative health practitioners and the supplement industry as superior to cyanocobalamin, primarily because it is a co-enzyme form of vitamin B12.
Based on many studies and case reports in the scientific literature in which cyanocobalamin has successfully cured vitamin B12 deficiency, it appears that the body can convert cyanocobalamin into methylcobalamin without any problem. The body also has to convert methylcobalamin or cyanocobalamin into adenosylcobalamin for B12 to carry out all of its functions. (A fourth form of vitamin B12, hydroxocobalamin, is the form typically found in animal products and B12 injections; it must also be converted into the co-enzyme forms.)
But is there any harm in taking methylcobalamin over cyanocobalamin? Probably not, but methylcobalamin is thought not to be as stable as cyanocobalamin and therefore higher doses are recommended, a minimum of 1,000 µg per day. Recommendations for cyanocobalamin are much lower (more info).
Some people with chronic fatigue report getting more relief from adenosylcobalamin than either methylcobalamin or cyanocobalamin (more info), while other people report feeling better only when taking both co-enzyme forms (adenosyl- and methyl-).
Cyanocobalamin supplements are ubiquitous, cheap, and well-studied, while methyl and adenosyl are much more of an unknown entity. Unless you have a good reason to be using them, I recommend cyanocobalamin.
Living Food Vitamin B12
Some companies claim to have a natural, living, plant, or raw source of vitamin B12. The B12 can come from seaweed or other unstated sources. Unless a label lists the source of vitamin B12 as cyanocobalamin, methylcobalamin, adenosylcobalamin, or hydroxocobalamin, I would not rely on it.
Specific Brands of Vitamin B12
I do not have recommendations regarding any specific brands of vitamin B12 supplements. As far as cyanocobalamin goes, I assume all sublingual or chewable tablets to be effective. I do not have an opinion on B12 skin patches or sprays.
As far as methylcobalamin supplements, as I stated above, I’m not as confident about them, and I have no opinion on any specific brand name.
Are B12 Supplements Vegan?
Yes. (More info.)
1. Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academy Press; 2000.