Vitamin B12occurs in foods that come from animals. Normally, vitamin B12 is readily absorbed in the last part of the small intestine (ileum), which leads to the large intestine. However, to be absorbed, the vitamin must combine with intrinsic factor, a protein produced in the stomach. Without intrinsic factor, vitamin B12 moves through the intestine and is excreted in stool.
Because vitamin B12 is necessary for the formation of mature blood cells, deficiency of this vitamin can result in anemia. The anemia is characterized by abnormally large red blood cells (macrocytes) and white blood cells with abnormal nuclei. Anemia may not develop until 3 to 5 years after the deficiency begins because a large amount of vitamin B12 is stored in the liver.
or cobalmaine deficiency can cause nerve damage (neuropathy) even when no anemia develops, particularly in people older than 60.
Causes of B12 deficiency
or cynacobalmine deficiency can result when people do not consume enough vitamin B12 or when the body does not absorb or store enough of the vitamin
very common in
Vitamin B12 deficiency develops in people who do not consume any animal products (vegans) unless they take supplements. If a vegan mother breastfeeds her infant, the infant is at risk of vitamin B12 deficiency.
The most common cause of vitamin B12 deficiency is inadequate absorption. The following conditions can cause absorption to be inadequate:
Overgrowth of bacteria in part of the small intestine
Inflammatory bowel disease
Fish tapeworm infection
Surgery that removes the part of the small intestine where vitamin B12 is absorbed
Drugs such as antacids and
Some Trade Names GLUCOPHAGE
(used to treat diabetes)
Lack of intrinsic factor
Decreased stomach acidity (common among older people)