What Does Intrinsic Factor Have to Do With B12?

When we talk about B12, we need to discuss “intrinsic factor.”

Several causes may lead to a B12 deficiency, but the usual reason one develops pernicious anemia is the inability to absorb the vitamin. The natural means of obtaining vitamin B12 is by way of the foods we eat, but B12 is not found in plants. You must eat protein foods such as liver, whole milk, eggs, oysters, pork or chicken, and its complex structure makes it much more difficult to absorb in comparison to other nutrients. In addition, the stomach secretes a substance known as “intrinsic factor” which binds to the B12 allowing it to be absorbed through the intestinal walls.


 An absence of vitamin B12 in the diet is seldom the cause of a vitamin B12 deficiency. It is much more common to find deficiencies in individuals who fail to absorb the vitamin from the intestine. This failure to absorb the vitamin results in pernicious anemia. The gastric parietal cells are responsible for the synthesis of a glycoprotein (a combination of carbohydrate and protein), called the “intrinsic factor”. When these cells are destroyed, the intrinsic factor is no longer produced and absorption of vitamin B12 is no longer possible.  Furthermore, as we reach the age of 50 and beyond, the stomach begins to produce less hydrochloric acid as well as less “intrinsic factor.” This is the condition that causes the elderly to have the inability to completely break down the protein in their diet, thus they are unable to free the protein-bound B12. This in turn creates the B12 deficiency.


 If an individual is missing or under producing “intrinsic factor,” it is not possible to absorb B12 regardless of how much one eats. The availability of “intrinsic factor” can also be affected by any type of stomach surgery, iron deficiency, pregnancy, aging, and intestinal disorders (like Crohn’s disease). Because of all these factors, many more people than generally recognized suffer from some level of B12 deficiency. 


 The “good news” to this is that when taking a sublingual B12 supplement, it does not matter whether or not you have any “intrinsic factor”, or even Crohn’s disease for that matter. The B12 will be absorbed directly into the bloodstream, thus by-passing any dependency on stomach hydrochloric acid or the production of the “intrinsic factor”.


 Next time, we’ll discuss how devastating a B12 deficiency can be.

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