Vitamin B12: Importance and Deficiencies

Vitamin B12 is a deep-red coloured water-soluble vitamin, called cobalamin. Of all the vitamins, B12 has the most complex structure. It is a coordination complex with a corrin ligand in the middle, with a benzimidazole ligand and an adenosyl group. This adenosyl ligand can be replaced by other chemical groups. It forms cyanocobalamin when the adenosyl ligand is replaced by a cyanide group. It may also form hydroxocobalamin or methylcobalamin when the adenosyl group is replaced by a hydroxide or a methyl group respectively. The vitamin is hence unique as it has a metal ion in its structure.  

Sources Of Vitamin B12 

The daily dose of Vitamin B12 can be achieved by taking foods rich in vitamins. Some of the sources of cobalamin include: 

  1. Green vegetables like broccoli, peas, spinach, beans, etc 
  2. Oranges 
  3. Sprouts 
  4. Wheat germ 
  5. Soybeans 
  6. Asparagus 
  7. Eggs 
  8. Meat 
  9. Poultry 
  10.  Shellfish 
  11.  Liver 
  12.  Fortified cereals 

Average Recommended Intake Of Vitamin B12 

The average dietary intake for Vitamin B12 for different age groups is given below: 

  1. Infants less than 6 months: 0.4 mcg 
  2. 7 to 12 months: 0.5 mcg 
  3. 1-3 years:  0.9 mcg 
  4. 4-8 years: 1.2 mcg 
  5. 9-13 years: 1.8 mcg 
  6. 14-18 years: 2.4 mcg 
  7. Adults: 2.4 mcg (2.6 mcg if pregnant and 2.8 mcg if breastfeeding) 

Functions Of Vitamin B12 

Vitamin B12

Some of the key functions of the vitamin B12 include: 

  1. Cofactor in DNA synthesis 
  2. Cofactor in fatty acid metabolism 
  3. Cofactor in amino acid metabolism 
  4. Synthesis of myelin 
  5. Maturation of red blood cells 
  6. Somatic cell metabolism 

Deficiency symptoms

Vit. B12 deficiency is related to the deficiency of cyanocobalamin.  

The common deficiency symptoms include: 

  1. Fatigue 
  2. Poor memory or dementia 
  3. Lethargy 
  4. Weak muscles 
  5. Numb feeling in the hands and the feet 
  6. Weight loss 
  7. Palpitation (noticeable heartbeats) 
  8. Breathlessness 
  9. Headache 
  10. Pale skin 
  11. Depression 
  12. Mouth ulcers 

In some cases, if the deficiency is highly severe, it may lead to 

  1. Psychosis 
  2. Irreversible brain damage 
  3. Irreversible damage to the nervous system 

Risk factors: 

The risk factors that may lead to Vit. B12 deficiency are: 

  1. History of deficiency 
  2. Gastric or intestinal removal 
  3. Autoimmune diseases 
  4. HIV 
  5. Strictly vegetarian or vegan practices 
  6. Prolonged medications (e.g. antibiotics, antacids, and anti-seizure medications) 
  7. Tapeworm infection 
  8. Increasing age 
  9. Pernicious anaemia 
  10. Chron’s disease 

Vitamin B12 Deficiency Anaemia (Megaloblastic anaemia): 

As Vitamin B12 is key to the maturation of RBCs, its deficiency results in anaemia. The condition is termed megaloblastic anaemia owing to an increase in the size of RBCs. An affected individual will not have enough RBCs which results in inadequate oxygen transport in the body. This results in a variety of symptoms like tingling, weight loss, fatigue, etc. Approximately, 1-2% of anaemia patients is deficient in Vit. B12

Cause: The major cause of Vit. B12 deficiency anaemia is a low intake of Vit. B12 containing foods, lack of intrinsic factor, intestinal infection, malabsorption of Vit. B12 or prolonged use of some medications. Vegans and vegetarians are at a higher risk compared to non-vegetarians. 

Diagnosis: A blood test is the easiest way to diagnose B12 deficiency anaemia. The parameters considered include levels of haemoglobin, folate and B12 in the blood and the number and size of RBCs.  

Treatment: The treatment options depend on the cause of the deficiency. If the deficiency is diet-related, you may have to include vit. B12 rich foods in the diet. If the deficiency is not diet-related, the treatment may include injections of hydroxocobalamin or cyanocobalamin.   

Complications: Some of the complications include neurological changes resulting in problems in vision, memory, body movement; infertility; stomach cancer, and neural tube defects in pregnant females. 

Vitamin B12 deficiency v/s Multiple Sclerosis 

Vit. B12 deficiency anaemia and multiple sclerosis are often misdiagnosed. The common symptoms of Vit. B12 deficiency and multiple sclerosis include muscle weakness, difficulty in walking, memory impairment and sensory disturbances. However, some symptoms can help us differentiate between the two. Vit. B12 deficiency affects both the central and peripheral nervous systems, affects the legs more than the arms and affects both the sides of the body equally. In multiple sclerosis, only the central nervous system is affected, affects all body parts equally and is predominant on one side of the body. 


The inclusion of Vit. B12 in our daily diet is of extreme importance because of the numerous functions it does in the human body. B12 improves heart health, supports good mood and healthy brain function. It also helps to tackle anaemia and is key for a good nervous system. It can also boost our energy levels, sleep, metabolism, cognition, and focus. It is good for skin, hair and nails. It gives mental clarity and helps with anxiety. 



One Comment