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Vitamin B12 and Intrinsic Factor

author image Charis Grey
For 15 years, Charis Grey's award-winning work has appeared in film, television, newspapers, magazines and on the Internet. She has worked as a story editor on the CBS drama "Flashpoint" and her work appears bimonthly in "The Driver Magazine." She has a Bachelor of Science in biology and a doctorate in chiropractic medicine from Palmer College.
Vitamin B12 and Intrinsic Factor
Raw oysters over ice. Photo Credit: JPC-PROD/iStock/Getty Images

Vitamin B-12 is the most molecularly complex of all the essential vitamins. Its effects are wide-ranging and crucial to many aspects of your health. Though this vitamin is readily available in many common foods, disorders related to the absorption of B-12 sometimes lead to deficiencies. A chemical called intrinsic factor, which is secreted by cells in your stomach, aids in the absorption of this vital nutrient.

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About B-12

B-12 is sometimes referred to as cobalamin, due to the presence of a cobalt ion within its molecular structure. Your body needs B-12 for nerve function, red blood cell formation, and the creation of substances such as DNA, hormones and proteins. When you consume B-12 in foods, it is bound to a protein that makes it difficult for your body to absorb. In your stomach, acids release B-12 from the protein that binds it, thus enabling the freed B-12 to bind with another gastric secretion: intrinsic factor.

About Intrinsic Factor

Intrinsic factor is a glycoprotein released by parietal cells that line the internal surface of your stomach. Without intrinsic factor, your body can only absorb about 1 percent of the B-12 you ingest. With the help of intrinsic factor, this amount increases to 56 percent of a 1 microgram dosage of B-12. However, Intrinsic factor has its limits. If you take dosages of B-12 that exceed the capacity of intrinsic factor – between 1 and 2 micrograms – absorption is decreased.

Conditions Affecting Intrinsic Factor

Some disorders can affect your ability to produce intrinsic factor and, consequently, your ability to absorb B-12. Pernicious anemia is an example of this type of malabsorption syndrome. If you have pernicious anemia, your body undergoes an autoimmune response that incorrectly identifies your parietal cells as a threat. Your immune system attacks and destroys these cells, thus compromising your ability to absorb B-12.

B-12 Deficiency

A deficiency in B-12 can take years to become apparent, as your body stores large amounts of B-12 in your liver. Once it does occur, however, B-12 deficiency is a serious matter. Adverse effects such as fatigue, weakness can be signs of megaloblastic anemia due to B-12 deficiency. B-12 deficiency can also cause nerve damage that affects cognitive and muscle function and can become permanent if not treated in time.

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