the "fruitarian problem"

i always read that the main problem why most fruitarians give up being fruitarian is the vitamin b12 deficiency which is very important for the body because it is needed for building red blood cells.

i like to avoid this and always read that this vitamin gets build by food and bacteria. so when u eat foods from the wild, unwashed with all the bacteria, this bacteria will build the b12. what is your opinion on this subject?