What Are The Causes Of Vitamin B12 Deficiency & Malabsorption?

Vitamin B12 is essential for the function of red blood cells and neurons. It participates in many enzymatic processes in the body. B12 can't be manufactured by the body--it need to be obtained from food. It can be stored in the body for several years. If there is a problem with supply or absorption, it generally takes several years before symptoms appear. There are several common causes of B12 deficiency. The risk of developing a deficiency is greatest among the elderly.

Pernicious Anemia

Pernicious anemia is an autoimmune condition in which cells lining the stomach's interior are attacked and destroyed by the body's own immune system. It can occur along with other autoimmune diseases such as Grave's disease, Myasthenia Gravis and Addison's disease. These cells produce intrinsic factor, to which B12 binds once it enters the stomach. The bound B12 then becomes available for absorption further down the gastrointestinal tract, in the small intestines. Without intrinsic factor, absorption is diminished, leading over time to B12 deficiency. Pernicious anemia can take decades to develop and usually appears after the age of 30.

Vegan Diet

B12 is present in foods from animals sources, nutritional yeast and fortified cereals. Adults should consume at least 2.4 mcg of B12 a day, more in certain conditions such as pregnancy. Vegetarians obtain B12 from milk and eggs -- a cup of yogurt provides about half the daily requirements -- but vegans are at risk of developing B12 deficiency. In order to get enough of the vitamin, people who follow vegan diets should consume either fortified cereals, one serving of which can contain 100 percent of the RDA, depending on the specific brand, or as an alternative, should take B12 supplements.

Fish Tapeworm

Fish Tapeworm, or Diphyllobothrium latum, lives in bodies of fresh water. Humans become infected when they eat undercooked or raw fish that contains tapeworm cysts. The tapeworm grows in the intestine and can reach lengths of 30 feet. It competes with the human host for the absorption of B12, thus leading to deficiency in the infected person.

Atrophic Gastritis

Atrophic gastritis is a condition that develops in older people, in which the lining of the stomach atrophies. As a result, production of acid decreases. Acid is needed to separate B12 from the food that contains it. If a significant portion of the lining is destroyed, B12 deficiency may occur.