TABLE 9-4Conditions That May Result in Vitamin B12 Deficiency

CausePathogenesis
Dietary deficiencyInsufficient B12 intake, as seen in complete vegetarians
Pernicious anemiaLack of intrinsic factor
GastrectomyLack of intrinsic factor
Atrophic gastritisInability to digest protein-bound B12 and bacterial uptake and/or conversion
Bacterial overgrowth of the small intestineBacterial uptake and/or conversion of B12
Infection with Diphyllobothrium latumUptake of B12 by the parasite
Terminal ileal disease or resectionInability to absorb B12
Pancreatic insufficiencyInability to digest protein-bound B12

From: 9, Vitamin B12

Cover of Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline
Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline.
Institute of Medicine (US) Standing Committee on the Scientific Evaluation of Dietary Reference Intakes and its Panel on Folate, Other B Vitamins, and Choline.
Washington (DC): National Academies Press (US); 1998.
Copyright © 1998, National Academy of Sciences.

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