# B-12 and the Intrinsic Factor

**URL:** <https://boards.straightdope.com/t/b-12-and-the-intrinsic-factor/93157>\
**Category:** Factual Questions\
**Created:** [November 13, 2001, 5:56pm UTC](https://boards.straightdope.com/t/b-12-and-the-intrinsic-factor/93157 "2001-11-13T17:56:36Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![barbitu8](https://avatars.discourse-cdn.com/v4/letter/b/839c29/32.png) [@barbitu8](https://boards.straightdope.com/u/barbitu8)\
**Post date:** [November 13, 2001, 5:56pm UTC](https://boards.straightdope.com/t/b-12-and-the-intrinsic-factor/93157/1 "2001-11-13T17:56:36Z")

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Years ago I read that some people, particularly some old farts, have problems absorbing B-12 from the intestines due to lack of the “intrinsic factor.” The name of this factor was never mentioned, apparently because no one knew what it was. Even until very recently, I’ve seen references to this intrinsic factor. Such persons need to have B-12 shots.

However, I just read in the November’s issue of \* Health \* the following:

> [@](#):
>
> Experts hae long known that older people don’t absorb B-12 well because they hae lower levels of stomach acid and the enzyme pepsin. These factors help digest protein, which is what the B-12 in food is attached to. That’s why the government’s National Academy of Sciences recommends that everyone over 50 get B-12 from a nutritional supplement or B-12 fortified cereal products. These sources contain the vitamin in its free form…

\*Health \*, I don’t believe, is a very reliable source. From this article, has the medical establishment determined that there is no intrinsic factor and nobody needs shots since everyone can absorb B-12 from supplements or cereals?

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**Author:** ![Bob\_Scene](https://avatars.discourse-cdn.com/v4/letter/b/e19adc/32.png) [@Bob\_Scene](https://boards.straightdope.com/u/Bob_Scene)\
**Post date:** [November 13, 2001, 6:47pm UTC](https://boards.straightdope.com/t/b-12-and-the-intrinsic-factor/93157/2 "2001-11-13T18:47:36Z")

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Intrinsic factor is a glycoprotein secreted by gastric parietal cells that binds to B[sub]12[/sub] in the digestive tract and then binds to receptors on cells in the small intestine so the vitamin can be absorbed. There’s an autoimmune disorder called pernicious anemia where the parietal cells are destroyed and so patients develop B[sub]12[/sub] deficiency.

But I think what your article is describing is another reason, besides lack of intrinsic factor, that some people can’t absorb B[sub]12[/sub]. The vitamin is usually bound to protein, and older people, because of a relative lack of stomach acid and digestive enzymes, have a harder time freeing it from the protein so it can bind to their intrinsic factor and be absorbed.

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**Author:** ![Bob\_Scene](https://avatars.discourse-cdn.com/v4/letter/b/e19adc/32.png) [@Bob\_Scene](https://boards.straightdope.com/u/Bob_Scene)\
**Post date:** [November 13, 2001, 6:51pm UTC](https://boards.straightdope.com/t/b-12-and-the-intrinsic-factor/93157/3 "2001-11-13T18:51:48Z")

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I want to add that people who lack intrinsic factor still need the shots. They can’t absorb enough dietary B[sub]12[/sub] in any form.

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**Author:** ![barbitu8](https://avatars.discourse-cdn.com/v4/letter/b/839c29/32.png) [@barbitu8](https://boards.straightdope.com/u/barbitu8)\
**Post date:** [November 13, 2001, 7:42pm UTC](https://boards.straightdope.com/t/b-12-and-the-intrinsic-factor/93157/4 "2001-11-13T19:42:54Z")

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Thanks Bob Scene, you answered my question. Moderators, please close this thread.