Vitamin B12 deficiency overview

Vitamin B12 deficiency Microchapters

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Overview

Historical Perspective

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Differentiating Vitamin B12 deficiency from other Diseases

Epidemiology and Demographics

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Natural History, Complications and Prognosis

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

## Overview

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B12 deficiency can potentially cause severe and irreversible damage, especially to the brain and nervous system.

The daily cobalamin (vitamin B12) requirement is 1-2 mcg. An intake of 5-20 mcg/day is usual in a Western diet. The total body can store 2-5 mg. 60% of vitamin B12 is efficiently absorbed via the ileum when it is bound to intrinsic factor (IF).

The first deficiency symptom that was discovered was anemia characterized by enlarged blood corpuscles, so-called megaloblastic anemia.

The anemia is thought to be due to problems in DNA synthesis, specifically in the synthesis of thymine, which is dependent on products of the MTR reaction. Other cell lines such as white blood cells and platelets are often also low. Bone marrow examination may show megaloblastic hemopoiesis. The anemia is easy to cure with vitamin B12.

Far more serious is the damage to the nervous system that may occur due to deficiency.

## Historical Perspective

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## Classification

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## Pathophysiology

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## Causes

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## Differentiating [Disease] from Other Diseases

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## Epidemiology and Demographics

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## Risk Factors

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For vegans, the risk is very high because none of their natural food sources contain B12. One American study found blood levels below normal in 92 % of vegans, 64 % of lacto-vegetarians, and 47% of lacto-ovo vegetarians.[1] The study applied the old normal values, so in reality a considerably greater proportion may have been deficient.

## Screening

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## Natural History, Complications, and Prognosis

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### Natural History

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### Complications

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### Prognosis

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## Diagnosis

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### Diagnostic Criteria

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### History and Symptoms

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### Physical Examination

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### Laboratory Findings

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### Imaging Findings

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### Other Diagnostic Studies

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## Treatment

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### Medical Therapy

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### Surgery

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### Prevention

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## References

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1. ↑ Dong A and Scott SC (1982). "Ann Nutr Metab 26(4):209-16".

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