Vitamin B12 is a vitamin important for normal functioning of nervous system and blood formation. It is generally agreed that there are no unfortified vegan foods that can be considered as reliable sources of this vitamin. That includes fermented foods such as tempeh, miso or sauerkraut, seaweeds, yeast, etc. Vitamin B12 is required in very small quantities. However, even if requirements are very low, missing it may have important and long term bad consequences.
The question whether vegans need to use vitamin B12 supplements remains controversial and complex. Some long-term vegans do not show any signs of B12 deficiency even after decades of no significant consumption of B12 supplements, while others need regular use of supplements to be optimally healthy. There are different theories why that happens, ranging from B12 production by bacteria in our digestive tract to getting enough B12 with some types of food that might have the vitamin in some conditions.
For those vegans who want to stay on a safe side, it is recommended to use B12 supplements on a regular basis. Vegan B12 tablets are produced by using controlled fermentation process and their production do not require any animal use or animal ingredients.