ROLE OF VITAMIN B12 AND ITS RELATED DISEASE IN HUMAN BODY

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 Introduction

Vitamin B12 is also known as Cobalamin and its water soluble vitamin  and the body can store vitamin B12  around 2-5 years. 

Its play a vital role in the nervous functioning ,blood formation and destruction, Cellular metabolism and DNA synthesized.

In nervous system vitamin B12 function as an enzyme to convert  methyl malonic acid  into Succinyl Co-A and this follow up the chain of reaction if vitamin B12 will be missing in this step Methyl melonic  acid will not get conversion into succinyl Co-A  as a result they accumulate in the nervous system they cause disturbance  in the metabolism of  fatty acid and myelin due to this nervous disturbance  happen in Vitamin B12 deficiency. 

In blood formation Vitamin B12 convert methionine into homocysteine that make S-adenosylmethionine that provide many methyl group for lipid, protein , neurotransmitter metabolism, cell function and  DNA regulation and at last it convert back   homocysteine into methionine because  homocysteine is dangerous blood vessels if Vitamin B12 will not available in the body these type of reaction in the will not occur properly as a result DNA regulation will failed that caused the abnormal ]formation of Blood cells happen and the other system that are associated with  these vitamin B12 they also get altered.

    

Vitamin B12 (Cobalamin ) has three units

*Central Cobalt atom

*Corrin ring

*Nucleotide side chain



Function of Vitamin B12

1. Role in DNA synthesis 

 *Vitamin B12 act as coenzyme 

* It activate Folic acid which is necessary for DNA synthesis 

*Formation of thymidine which is important for DNA replication and repair.

* Purine is the basic structure of DNA  and Vitamin B12 is essential for the formation of purine

 2. Role in energy metabolism

* It doesn't provide energy like glucose but help in energy production.

* It act as coenzyme and convert food into usable energy like ATP.

* Vitamin B12 play a vital role in the DNA synthesize especially in rapid growth cell like RBCs

* Healthy RBCs transport oxygen efficiently we can say that it play a role in oxygen transportation 

* Its essential for myelin synthesis and nervous conduction

*It regenerate active folate which is essential for nucleotide  formation

3. Role in nervous systems 

* It is essential  for myelin synthesis and its maintenance ( myelin is a protective  covering around the nerve) e.g it convert  Methylmalonic acid into Succinyl Co-A when this reaction will not proceed Methylmalonic acid cause decrease the metabolism of  fatty acid and myeline  in nervous system.

* Role in DNA synthesis in nervous that is necessary for supporting nerve cell

* it is important in neurotransmitter synthesize e.g methionine synthesis ( it is necessary for SAM formation  and same play a vital role in mood regulation and cognitive function) SAM provide methyl group for several reaction.

* It protect again nerve degeneration 

for more about nervous  system visit this page https://www.healthduhs.org/2026/05/what-is-nervous-system-and-how-it-is.html


4. Role in homocysteine system

* It reduce the concentration of homocysteine ( It is an amino acid in blood  that is produced from  methionine ) higher concentration of homocysteine cause several heart problems.

Step of  Vitamin B12 absorption 

* Dietary B12 bind to proteins in stomach called intrinsic factor  and it makes  vitamin B12 absorbable in the small intestine

* Free B12 binds with haptocorrin ( which is released by saliva and stomach)

* B12 + R- protein moved towards small intestine

* Small intestine again release free Vitamin B12 

* Stomach again release  intrinsic factor which again bind with Vitamin B12 that is essential for  absorption 

*Distal ileum contain specific receptor which recognize B12 complex  and it absorbed here via endocytosis

* B12 released from Intrinsic factor after endocytosis and bind with transcobalamin2

* Which carry B12 to from plasma to liver, bone marrow and tissue

* it store mainly in liver 2-5 mg

* It store in human body for 3 - 4 years

 for more about how absorption happen small intestine visit this page https://www.healthduhs.org/2026/04/what-is-function-of-human-intestine.html

Sources of vitamin b12

It is naturally found in animal not in plant

* Red meat

* Eggs

* Liver

* Poultry

* Fish

* Milk

* Yogurt 

* cheese 

* Fortified plant milk

* vitamin B12 supplements

* Fortified cereals

Requirement of B12

*Pregnancy

2.6 µg/day

*Lactation

2.8 µg/day

*Children

0.9–2 µg/day

*Adults

2–3 µg/day

 Sign and Symptoms of  Vitamin B12 Deficiency

* Shortness of breathing

* Weakness

* Fatigue

* Megaloblastic anemia

*  Pallor

* Difficulty in walking 

* Memory loss

* Depression

* Dementia

*Mouth ulcer

* Diarrhea

* weight loss 

* Loos of appetite 

* Beefy red tongue

Causes

* Malnutrition

* Vegetarian

* Choronic alcoholism

* proton pump inhibitor

* long term usage of metformin

*Gastrechtomy

* Celiac disease

Prevention

Take these items as per mentioned on  the above requirement 

*Red meat

* Eggs

* Liver

* Poultry

* Fish

* Milk

* Yogurt 

* cheese 

* Fortified plant milk

* vitamin B12 supplements

* Fortified cereals

Treatment of B12 deficiency

*  when absorption is disturbed Injection therapy should be recommended

* Intramuscular for patient with initial case 1000ng daily in 1 week

* 1000weekly in 4 weeks for secondary case

* 1000mg in 1 month for life time for severe case and life time treatment

* Oral therapy is available if patient deny from injection 

For more about other vitamin e.g vitamin A visit this sitehttps://www.healthduhs.org/2026/02/importance-and-deficiency-of-vitamin-in.html

Diagnostic test for Vitamin B12

 During the assessment of patient if the sign and symptoms compel the patient toward Vitamin B12 deficiency, we will perform these tests

*    CBC test

*    Serum Vitamin B12

*    Methylmalonic acid 

*    Homocysteine

*    Folate  

Reference


 WHO -World Health Organization
NIH- National Institute Of Health)

 CDC- Centre for Disease Control and prevention


 


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