This can actually be good for elderly who do not make enough intrinsic factor or those who have had parts of the stomach and intestines removed. Vitamin B12 shots have been given by doctors for tiredness, lack of energy, etc for decades. Objective testing of this conclusively demonstrated no benefit over a placebo. However, some doctors still give B12 injections to elderly patients for non-indicated conditions. The only indication for B12 injections is a demonstrated deficiency of the vitamin.
Rich sources are liver and kidney.
High sources are egg yolk and seafood. B12 is also found in lean meats, fish and dairy products. Vegans must take supplements. Some yeasts are grown under conditions that enrich them in vitamin B12 but not all yeast provides B12. The claim that not washing vegetables leaves enough bacteria containing vitamin B12 is simply not true.