Vitamin B12, or Cobalamin, is an essential vitamin necessary for the maintenance of the nervous system and for preventing anemia. A slight deficiency of vitamin B12 can lead to anemia, fatigue, mania, and depression, while a long term deficiency can potentially cause permanent damage to the brain and central nervous system.
Vitamin B12 is synthesized by micro-organisms and can be found in some natural vegan foods like tempeh, seaweed, mushrooms, beer, wine, and yeast extract spread. Unfortunately, the amount of vitamin B12 in these foods can vary greatly, and even when they do contain vitamin B12, it is likely they do not contain enough to be a good source of vitamin B12 over the long term.
Due to bio-accumulation and biomagnification meats and animal foods typically provide more vitamin B12, however, this same bio-accumulation effect is what makes meat accumulate metals and other toxins. Avoiding these toxins in meat is one of the health benefits of veganism.
Without reliable natural vegan sources of vitamin B12, and without animal food products, fortified vegan foods are the only reliable and consistent source of vitamin B12 for vegans. Healthy vegan foods fortified with vitamin B12 include commercial cereals, fruit and vegetable juices, dairy substitutes, fortified tofu, and vitamin waters. Since all these foods have vitamin B12 added to them, their levels can vary greatly. Check product labels before buying.
In addition to the fortified foods above, supplements can also be a cheap, healthy, and effective option to get enough vitamin B12. Below is a list of vegan foods highest in vitamin B12, for more, see also the article of vegetarian foods highest in vitamin B12, and cereals high in vitamin B12.