Vitamin B12

What is vitamin B12?

Vitamin B12, also known as cobalamin(e) because it contains cobalt, is a very important essential nutrient: among other things we use it to synthesise red blood cells and maintain the health of our nervous systems and deficiencies can cause all sorts of neurological damage. Vitamin B12 is unique in that it is manufactured solely by micro-organisms that are commonly found in the soil around the root networks of plants. Animals that eat these plants also ingest some of these micro-organisms that then continue to produce a B12 supply from within their gut.

Our evolutionary relationship to dietary B12 can thus be seen to have developed either from eating animals or from eating unwashed plants. In either instance though, it’s not the animal or the plant that is supplying us with our B12, it’s the micro-organism that lives in or around the plant or animal.

Many non-vegans oversimplify the B12 issue, stating bluntly that there are just no non-animal sources of B12. This would be disastrous as deficiency can result in blindness, brain-damage, infertility, miscarriage and children with impaired cognitive ability and major skin and muscle wasting.

This is worrying, but do vegans have to be specifically concerned about B12 deficiency?

Causes of deficiency

There are several causes of B12 deficiency in both vegans and the general population. While lack of dietary intake is prominent amongst these, a significant percentage of people (including up to 30% of the elderly[1]) cannot absorb naturally occurring B12 due to conditions like intrinsic factor deficiency or celiac disease.

Deficiency and diet

While vegans are at greater risk of B12 deficiency if they do not supplement, it is interesting to note that almost 40% of the US population show very low levels of B12, and that these levels (below 258 picomoles per liter [2]) have been correlated with symptoms of deficiency. An equally worrying percentage of people in developing countries also show serious deficiency, possibly due to pathogen-related malabsorption, poor sanitation or similar issues.

For now, however, let’s accept that vegans are at specific risk of developing B12 deficiency if they do not supplement or consume fortified foods.


The daily requirement for B12 is between 1-3 micrograms (1-3 millionths of a gram). Some professionals suggest taking this amount daily, and most daily multivitamins thus contain several micrograms of cobalamin (up to several hundred micrograms in some cases). Others suggest a much larger weekly dose, leading to the provision of weekly dedicated B12 supplements that contain 100mcg or more (it should be noted that your body stores B12 for a reasonably long time – you only lose around 0.1% of your reserves per day. It will, however, eventually run out if you’re not taking enough in).

These supplements are the best way to obtain dietary B12 and should be taken by anyone who is not certain of their B12 status, vegan or not.

Historically, people have promoted countless other ‘natural’ sources of B12: micro-algaes like spirulina and chlorella, fermented soy products like tempeh and miso, and seaweed and sea vegetables like nori, arame and wakame, etc. However, apart from the fact that the levels of naturally occurring B12 in these foods can vary greatly, they usually contain only the inactive analogue of the vitamin, which not metabolized by humans even though it does show up in tests. In fact, these analogues may actually interfere with the metabolism of active B12.

One of the reasons for the continued promotion of non-supplementary sources of B12 is that there are prominent examples thereof: rural Chinese people for example, some of whom are, for all intents and purposes vegan, don’t display the symptoms we would usually attribute to B12 deficiency.

Indonesians who consume tempeh regularly also don’t seem to suffer from deficiency; it is thought that this is due to B12 producing bacteria that grow on certain kinds of mold that grow on the tempeh. [3][4]

In both cases though, industrial production and processing of food in developed countries dramatically decreases the amount of bacteria, molds, etc. that grow on our foodstuffs, and so we cannot rely on these same sources.

Some people also think that the human gut (or even mouth) contains sufficient concentrations of the necessary micro-organisms to produce ample B12; this is far from proven though, and is likely not to be the case.

Vegans who do not want to use supplements (even though supplementary B12 almost always comes from the same place you would obtain it if you ate unwashed vegetables, moldy tempeh or animal liver: micro-organisms) can still choose to consume fortified breakfast cereals, fortified soy milks (almost all of them tend to be these days), or fortified meat substitutes.

Even energy drinks like Red Bull contain Vitamin B12, although it should be noted that this is often included as a replacement for vitamins that the caffeine stops your body from absorbing.

More about B12

  • Vit B12, or cobalamin(e), is an essential nutrient used among other things to synthesise red blood cells and maintain the health of our nervous systems.
  • Vitamin B12 is manufactured solely by micro-organisms that are commonly found in the soil around the root networks of plants. This is how animals produce B12 in their gut.
  • It is recommended that to ensure adequate B12 vegans must either supplement, consume fortified breakfast cereals, fortified soy milks, or eat fortified meat substitutes.

In conclusion

In short, B12 is not a real concern for vegans if they are willing to supplement (which is an exceedingly small price to pay for the arguable ethical, health and environmental advantages the vegan diet confers) or simply make sure their soy milk and breakfast cereal contain sufficient amounts of B12/cobalamin(e). While the rather dramatic list of symptoms of deficiency does represent the realistic worst case scenarios of severe lack of dietary B12, these are entirely avoidable at all ages of life (via breastfeeding at birth right through to increased supplementation in old age) through simple supplementation and fortification.



[1] US Institute of Medicine –
[2] Katherine Tucker and Jean Mayer – USDA Human Nutrition Research
[3] Areekul S, Churdchu K, Pungpapong V. Serum folate, vitamin B12 and vitamin B12 binding protein in vegetarians. J Med Assoc Thai 1988 May;71(5):253-7.
[4]. Areekul S, Pattanamatum S, Cheeramakara C, Churdchue K, Nitayapabskoon S, Chongsanguan M. The source and content of vitamin B12 in the tempehs. J Med Assoc Thai 1990 Mar;73(3):152-



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