I often hear "I had to go back to eating animals, because I was b12 deficient." It's worth considering if veganism caused this deficiency or if it was pre-existing. Needs for it can be easily established in carrots, squash, apricots, papaya, broccoli, mangoes, avocado, peaches, peppers and melons.
It's very easy to throw in a clip and paint veganism with an entire broad brush stroke by onlookers who don't care to know any better. However, the same careless method could be used for any person or practice in life which is the opposite approach of what God's word encourages us to do. There's so many misunderstandings and prejudices against the lifestyle and it takes earnest study and care about food, health and ecosystems to appreciate the value in it all, otherwise the false claims just amount to no motivation and indifference towards it all.
The B12 is a water soluble vitamin. It is a bacteria found in soil and it's essential for formation of red blood cells and in the health of our nerve tissue. B12 is unique because it has a trace mineral called 'cobalt' and hence the scientific name cobalamin. Cobalt is found in the soil and if the soil is deficient which a lot of our soil today is from modern farming methods, then there is no b12 in the produce. Without cobalt, you cannot create b12. Contrary to popular meat and dairy industry propaganda and well meaning doctors, eating meat, seafood, dairy and eggs does not protect you from b12 deficiency. In addition it can make you more susceptible to b12 deficiency as meat will not provide you b12 since there's many processes between the ingestion and absorption.
Humans aren't designed to eat meat therefore our bodies are not equipped to deal with the unnaturally high doses of hydrochloric acid produced in an attempt to digest it (affecting b12 production and absorption). If you're interested in learning and changing, consider raw, organic kale and seaweed, if not, I'll leave you to the consequences of the ensuing lifestyle.