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Published on: November 27, 2016
Vitamin B12 absorption and malabsorption
Jean-Louis Guéant1, Rosa-Maria Guéant-Rodriguez2, David H Alpers3
1University of Lorraine, INSERM UMR_S 1256, Nutrition, Genetics, and Environmental Risk Exposure (NGERE), Faculty of Medicine of Nancy, Nancy, France; Department of Biochemistry, Molecular Biology, Nutrition, and Metabolism, University Hospital of Nancy, Nancy, France; Department of Hepato-Gastroenterology, University Hospital of Nancy, Nancy, France.
Vitamin B12 absorption involves complex transport proteins and receptors. Malabsorption stems from dietary issues or digestive diseases, necessitating new diagnostic tests.
Area of Science:
- Biochemistry
- Gastroenterology
- Nutrition Science
Background:
- Vitamin B12 (cobalamin) absorption is a complex physiological process.
- Deficiency often results from inadequate dietary intake (vegans) or malabsorption linked to digestive disorders.
Purpose of the Study:
- To review the physiology of vitamin B12 absorption.
- To explore mechanisms and diseases causing vitamin B12 malabsorption.
- To highlight the need for reliable diagnostic tests.
Main Methods:
- Literature review of vitamin B12 absorption physiology.
- Analysis of transport proteins: haptocorrin (HC), intrinsic factor (IF), transcobalamin (TC).
- Examination of receptor mechanisms involving cubilin and amnionless.
Main Results:
- Vitamin B12 binds to HC in the stomach, then transfers to IF in the duodenum.
- Receptor-mediated uptake occurs in the distal ileum.
- Numerous conditions cause malabsorption, including inherited disorders, digestive diseases, and post-surgical states.
Conclusions:
- Genetic causes of B12 malabsorption may be underestimated.
- Current diagnostic methods like the Schilling test are inadequate.
- There is an urgent need for a reliable alternative test for B12 malabsorption.
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