well there are many reasons to become B 12 deficiant , one main reason is that metformin actually lowers ones abillity to uptake vitamin B 12 ... and maybe think metfomine even damage the cells in the intestines that are the only ones that can uptake vitamin B 12 , otherwise one has to have injections of vitamin B 12 .... vegans dont get enough vitamin B 12 because vitamin B 12 is only found in foods made of animal stuff also like eggs...
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hen becomming older some also loose the abillity to uptake vitamin B 12 and in previous times they would have has a miserable life and died initially..
usualy the liver has a store of vitamin B 12 that can last up til 6 years , so going vegan will many times not result in a measuralble deficiency untill many years later like 6 years after becomming vegan, .. it is thought though that the body tries to save vitamin B 12 for the most essential use in the body , but the symptoms and damage that is unfortunately very often ireversible are nerve damage ....
the autoimune reactions toward ones own body and different functions also seem to cause a higher rate of diabetes and also casue sometimes the damage of these very special cells in the intestine that can uptake vitamin B 12 which maybe why there are many people in this forum having a lack of vitamin B 12 ...
there are reasosn for the deficiensy but the causing reason are many times not the same... it is a known fact that vegans very often end up with vitamin B12 deficiency.. many do "sin" and eat some animal stuff on seldome occasions and thereby delate the time where they´ll get this damage that vitamin B 12 deficiency causes...
Even vegan organisations aknowledge this problem , so it is certainly not something I have found up for being rude to vegans, and yes it can be taken as pill suplement which is why I believe humans were not truely ment to be pure vegans ... some do avoid even taking pills as they think that is also un-natural and that is a problem if one is vegan...