Vitamin B12 deficiency can occur in anyone at any age.

Both vegans and non-vegans can suffer from B12 deficiencies. Vegans may suffer because of low intake; others due to the inability to absorb B12.

Vitamin B12 is absorbed by the intrinsic factor in the stomach. High proteins from meat and milk force the stomach to produce more acid to digest them. (Proteins are digested mainly in the stomach.) This high acid secretion not only causes acidity but also destroys the lining of the stomach so that the intrinsic factor is deficient. Thus, vitamin B12 is not absorbed.

When the deficiency is due to a lack of intrinsic factor, B12 tablets will not help, and injections are required. Deficiencies could also be the result of bacterial flora being destroyed by antibiotics or because of deficient intake of bacteria in our unnaturally sterile food.