Relationship between Vitamin B12 and the intrinsic factor

Carlos Sánchez 5 min. of reading Vitamins 1 Comment

Did you know that vitamin B12 needs intrinsic factor to be properly absorbed by the body?

In this article, we explain the crucial connection between this vitamin and intrinsic factor for your health and energy, answering all your questions about this important process.

What is intrinsic factor?

Vitamin B12 is a nutrient obtained from eating animal-based foods. For the body to absorb it, B12 must pass through the wall of the small intestine. Due to its size, this is only possible with the help of a specific transport mechanism. This is where intrinsic factor comes into play, a protein that helps B12 cross the intestinal wall and be absorbed.

Without intrinsic factor, vitamin B12 can only be absorbed in small amounts through a process called passive diffusion, rather than the active transport used by intrinsic factor.

How does intrinsic factor help absorb vitamin B12?

When we eat, vitamin B12 binds to proteins in food. As we chew, B12 mixes with saliva and stomach acid. Gastric acid releases B12, which then binds to a protein called R-protein. Although R-protein helps transport B12, intrinsic factor is more effective for absorption.

Intrinsic factor binds to B12 and transports it via a receptor in the ileum, the final part of the small intestine, allowing the body to absorb the vitamin properly.

Where is intrinsic factor produced?

Intrinsic factor is produced in the parietal cells of the stomach lining. These cells generate it in quantities that exceed the body’s physiological needs.

Although it is not yet fully understood why it is produced in such high amounts, experts believe its main function is to facilitate vitamin B12 absorption in the final part of the small intestine.

When is intrinsic factor not produced?

In some cases, the body does not produce intrinsic factor, which can negatively affect its ability to fight infections. This can happen for several reasons:

Hereditary absence of intrinsic factor.
Mutation of the gene encoding intrinsic factor.
A condition similar to HIFD known as Imerslund-Gräsbeck syndrome, which results in poor vitamin B12 absorption.

How is vitamin B12 deficiency treated when intrinsic factor is absent?

If you are in one of the situations mentioned above, there is no major cause for concern, as the absence of intrinsic factor can be compensated with a high dose of vitamin B12. In this case, cobalamin absorption occurs through passive diffusion across the intestinal wall.

Since only about 1.2% of the absorbed vitamin B12 is used by the body, a very high daily dose of cobalamin is necessary, ranging between 1,000 and 2,000 micrograms.

Autoimmune reaction against this factor

Pernicious anaemia is an autoimmune disease characterised by the production of antibodies against intrinsic factor. These antibodies bind to intrinsic factor, preventing vitamin B12 from attaching to it and being transported through the intestinal wall.

What happens when intrinsic factor production is insufficient?

In some cases, the body does not produce enough intrinsic factor to absorb the required amount of vitamin B12. This insufficient production may be due to several causes:

Ageing: A study revealed that between 1% and 2% of people over 70 years old do not produce enough intrinsic factor.
Loss of function of parietal cells: These stomach cells can be affected by diseases such as AIDS, leading to reduced production of stomach acid, pepsin, and intrinsic factor.
Surgical intervention in the digestive tract: Procedures such as gastric bypass or gastrectomy (partial removal of the stomach) can result in the loss of parietal cells, reducing or eliminating intrinsic factor production.

Intrinsic factor and its link to infections

The relationship between bacterial infections and intrinsic factor is reciprocal. On one hand, bacteria can negatively affect vitamin B12 absorption by interfering with intrinsic factor. On the other, intrinsic factor plays a crucial role in fighting infections.

Vitamin B12 and gastrointestinal conditions

Finally, let’s examine the relationship between cobalamin and certain gastrointestinal conditions:

Malabsorption syndrome: The main cause of vitamin B12 deficiency is malabsorption syndrome, which generally occurs when the stomach lining loses its ability to produce intrinsic factor.
Gastric acid deficiency: Conditions such as oesophagitis and indigestion, caused by acid reflux, may result from excessive or insufficient gastric acid production. The use of acid blockers, common in people with indigestion and heartburn, can inhibit the production of hydrochloric acid needed for digestion and nutrient absorption.

The lack of stomach acidity makes digestion difficult and reduces the amount of nutrients absorbed.

In conclusion, intrinsic factor is crucial for vitamin B12 absorption, which is essential for the body’s energy. If you have a deficiency or insufficient production of this factor, adequate vitamin B12 supplementation may be the solution.

Complete vitamin B12 catalogue

References

Neale G. B12 Binding Proteins. Good, 1990, 31, 59-63.
Se Arregló HP. Intrinsic Factor Secretion and Cobalamin Absorption. Physiology and Pathophysiology in the Gastrointestinal Tract. Scand J Gastroenterol Suppl. 1991; 188: 1-7.
Kapadia CR. Vitamin B12 in Health and Disease: Part I – Hereditary Disorders of Function, Absorption, and Transport. Gastroenterologist. 1995 Dec; 3 (4): 329-44.
Boina Abdallah A, Ogier de Baulny H, Kozyraki R. How Can Cobalamin Injections Be Spaced in Long-Term Therapy for Congenital Errors of Vitamin B(12) Absorption? Mol Genet Metab. 2012 Sep; 107 (1-2): 66-71.
Berlin H, Berlin R, Brante G. Oral Treatment of Pernicious Anaemia with High Doses of Vitamin B12 Without Intrinsic Factor. Acta Med Scand. 1968 Oct; 184 (4): 247-58.

Related Posts