With a B-13 deficiency a host of nervous system problems can develop including depression and memory loss. When deficiency hits, it can be devastating to the individual and their family if it is not diagnosed and treated quickly. Most Americans consume plenty of B-12 in meat, poultry, fish, eggs and milk products. B-12 deficiency commonly stems from a reduced ability to absorb it from food. Normal stomach acid and enzyme levels are needed to make B-12 available for absorption.
Many older people experience a decline in the secretion of stomach acids.
Also, many drugs or antacids taken for stomach problems interfere with the function of stomach acid, further impairing the release of B-12 from food. In these forms, the vitamin is not bound to protein, so its absorption is not impaired by low stomach acid production. A small percentage of those with B-12 deficiency have a condition called pernicious anemia. With this condition, they can't absorb B-12 even from supplement sources. The usual treatment is monthly injections of B-12 for the remainder of the person's life.