B12 is necessary to our well-being. It is naturally produced from a ground fungus being consumed by animals, when they are wild or grass-fed. You get B12 from eating and drinking foods (eggs, dairy) from fish and animals that pick up the fungus, which contains the bacteria that animals absorb in their guts and into their systems. .

Factory farms feed livestock grains that are unnatural - corn, soy and many other things that are terrible for the animal digestive system. Corn and soy are likely GMO as well. The diet of these poor animals have been altered completely from their natural diets. The nutrition in factory-farmed meat is absolutely not the same as it is in wild or pasture-raised animals. And B12 is sadly lacking - since they aren't able to feed on dirt that contains the fungus needed to produce B12.

B12 is needed for the production of healthy red blood cells, for synthesis of DNA, and for neurological function. It is needed to metabolize fat and protein. It is needed to synthesize hemoglobin. B12 ultimately is needed to maintain proper function of DNA, RNA, protein lipids, and hormones.

B12 deficiency can cause anemia, fatigue, weight loss, weakness. Neurological disorders may and have occured. B12 deficiency may cause tingling (feet or hands "go to sleep"), numbness, memory issues, balance issues, etc.

To find out your B12 level - you need a blood test. If deficient, you need to supplement B12 by the amount your doctor tells you.

Non animal B12 sourses include fortified foods, minerals and supplements, and shots. B12 suplementation needs to be in uncooked sources, and kept in the dark. Yeasts may be fortified with B12 - but look for the ones that are.

I learned much about B12 when I was tested to be low, even though I was eating fish and game meat. I may not be absorbing it well, or may not be eating enough meat daily, or both in combination. With supplementation I have stabilized the B12 level.