Vitamin B12 is naturally found in animal foods. It can also be added to foods or supplements. Vitamin B12 is needed to form red blood cells and DNA. It is also a key player in the function and development of brain and nerve cells.
Vitamin B12 binds to the protein in the foods we eat. In the stomach, hydrochloric acid and enzymes unbind vitamin B12 into its free form. From there, vitamin B12 combines with a protein called intrinsic factor so that it can be absorbed further down in the small intestine.
Signs of deficiency may include:
- Megaloblastic anemia—a condition of larger than normal sized red blood cells and a smaller than normal amount; this occurs because there is not enough vitamin B12 in the diet or poor absorption
- Pernicious anemia—a type of megaloblastic anemia caused by a lack of intrinsic factor so that vitamin B12 is not absorbed
- Fatigue, weakness
- Nerve damage with numbness, tingling in the hands and legs
- Memory loss, confusion