Vitamin B12 (cyanocobalamin) Deficiency

What is Vitamin B12?

Vitamin B12 is a water-soluble vitamin that is critical for red blood cell formation, cell metabolism, nerve function and production of DNA. Vitamin B12 is also called cobalamin. Vitamin B12 is solely synthesized by gut microflora bacteria and archaea either aerobically or anaerobically. 

What are natural sources of Vitamin B12?

Upon dietary uptake, vitamin B12 binds to a specific protein called intrinsic factor, secreted by gastric parietal cells, that facilitates absorption of Vitamin B12 into bloodstream.

Dietary sources of Vitamin B12 include:
•    Animal products - Meat, liver, kidney, eggs, milk, fish, and shellfish
•    Fortified food- Fortified breads, crackers, and cereals. 

What are the symptoms of Vitamin B12 deficiency?

Human body can store Vitamin B12 for several years, so it takes time to develop any symptoms of b12 deficiency. 

Usual signs of vitamin B12 deficiency are
•    Numbness or sensation of pins and needles in hands, feet, or legs
•    Shivering and cold
•    Mental symptoms such as depression, confusion, memory problems, and dementia
•    Weakness, loss of appetite, weight loss, constipation, swollen or inflamed tongue, heart palpitations, anaemia, nerve damage, moodiness, mouth ulcers.

What causes of Vitamin B12 deficiency?

Common causes include age, lack of intrinsic factor, strict vegan or vegetarian diet, genetic or polyglandular autoimmune syndrome.

Sometimes consumption of certain medication (ex: chloramphenicol, omeprazole, metformin, cimetidine) can also result in Vitamin B12 deficiency via to drug interactions. Rarely it can also be induced by nitrous oxide.

How Vitamin B12 deficiency and anaemia are related?

Vitamin B12 deficiency, along with folate deficiency, is strongly linked with Megaloblastic anaemia, a condition arising due to decreased DNA synthesis and immature nuclei in hematopoietic precursor cells. Pernicious anaemia is a type of megaloblastic anaemia where body is not able to absorb vitamin B12 due to a lack of intrinsic factor. 

There are also neurologic abnormalities such as demyelination of the central nervous system causing psychiatric, cognitive, and proprioceptive disorders, are also clinical implications of Vitamin B12 deficiency.

How to diagnose Vitamin B12 deficiency?

Rather than diagnosing Vitamin B12 deficiency via a B12 serum test and comparing it to normal levels (140-450 pmol/L), some physicians may diagnose B12 deficiency by the presence, or absence, of metabolites generated from Vitamin B12 insufficiency. Elevated methylmalonic acid and homocysteine levels in body fluids or tissues are direct indications of vitamin B12 deficiency.

What is treatment for Vitamin B12 deficiency?

The most common treatement for treating B12 deficiency is by using oral dosage forms such as tablets of 1000–2000 mg/day. If oral therapy is not suirtable, then vitamin B12 (Cyanocobalamin) 1000mcg/ml injection is given by either intramuscular or subcutaneous routes.

What is recommended daily intake of Vitamin B 12?

•    Recommended daily intake of Vitamin B12 is 2.4 μg/day (For adults, with assumption of at least 50% absorption). 
•    For pregnant and lactating women, high doses of 2.6 and 2.8 mg are recommended. 
•    Foods fortified with vitamin B12 or a vitamin B12-containing supplement is advised for 50 plus age group.