Vitamin B12 also called as cobalamin is an essential vitamin without which the body cannot function. It is present in various forms like methylcobalamin, cynocobalamin etc.
How much does the body require ?
The daily requirement of B12 is very small, about 2-3 ug (micro grams). 1000 ug=1 gm.
How do we get B12 ?
B12 is not produced in the human body. B12 also is not a part of any food of plant origin. Only food of animal origin contains B12. For persons with a vegetarian diet, milk and dairy products is the only source of B12.
Physiology of Vitamin B12
Absorption of B12 is a 2 step process.
1. The cells of the stomach lining that secrete acid also produce a substance called as intrinsic factor. This factor binds with B12 that is present in food.
2. This complex of intrinsic factor and B12 is then absorbed in the distal (last) part of the small intestine called as ileum.
In the absence of intrinsic factor, only 1% of B12 in food can get absorbed.
What are the causes of B12 deficiency ? There are several causes. a. Poor dietary intake (Vegetarian diet), b. Defect in production of intrinsic factor.
c. Defects in digestion .
d. Antacids that suppress acid producing cells of the stomach, also decrease the production of intrinsic factor.
e. Autoimmune diseases that destroy the lining of acid producing cells. (Pernicious anaemia)
History of B12.
It has been known since ancient times that some persons developed an unexplained disease which resulted in decrease in haemoglobin, and the person appearing almost white. This disease had no known cure and was fatal in 3-5 years. This disease has also been described in Mahabharat as Pandu Rog.
In 1824 it was first realised that B12 deficiency was a disease related to a disorder of the digestive system and was called as pernicious anaemia. In 1887 it was shown that neurological symptoms are also seen in pernicious anaemia.
In the early 1920s, most doctors believed that pernicious anaemia was caused by a toxic substance in the body, and they prescribed doses of arsenic, transfusions, or removal of the spleen as treatments. But after these remedies were administered, patients had relapses. Death was inevitable. Across the world, 6,000 lives a year were lost to the scourge of pernicious anemia.
It was as recently as 1928 that Minot and Murphy treated pernicious anaemia using liver extracts. Animal liver is rich in B12. When huge quantity of B12 is given orally, small quantity can get absorbed without intrinsic factor, resulting in correction of B12 deficiency. It was only in 1950 that B12 was purified and is now available to us in oral or injectable form.
Discovery and purification Vitamin B12 is a precious discovery of modern medicine which now saves life of thousands of patients.
What is the function of B12 ?
It has 2 functions.
a. It is required for the production of DNA and RNA and is thus required by by every cell in the body. In the absence of B12 cells in the body cannot produce DNA and RNA and are thus unable to divide.
Deficiency of B12 affects the rapidly dividing cells like platelets and WBC the most, resulting in low platelet counts and low WBC counts.
b. B12 is also required by nerve fibres or maintenance of myelin sheath (covering of nerve fibres). In the absence of myelin, nerve functions slows down and a person has difficulty maintaining balance.
Not all patients have all symptoms. In fact most patients with B12 deficiency have just a mild anaemia and complain of low energy levels.
How do we diagnose B12 deficiency
This is done by testing the blood. Reports are usually available the same day. Levels of more that 300 pg/ml in blood are adequate. Please note that B12 levels in blood are in picograms . 1 picogram is 10-12 grams a very small quantity.
How do we treat B12 deficiency ?
Most patient require oral supplementation. Some patients require B12 in a injectable form. After treatment, levels of B12 in the blood can go high and are frequently reported as More than 2000 pg/ml. This can happen even after a single injection.
How is B12 stored in the body ?
B12 is stored in the liver. In normal persons the stores are sufficient to last for 2-3 years even if the person does not take oral B12. So when we see a patient of B12 deficiency, we conclude that the factors that produce B12 deficiency must be there for more that 2-3 years.
Who requires to check B12 levels ?
a. Vegetarians are more likely to develop B12 deficiency because of diet.
b. In pregnancy requirements of B12 increase
c. Any person with digestive problems.
d. Patients with anaemia (low haemoglobin)
B12 is a very important molecule required by the body. Low levels can produce severe problems. Blood tests can easily detect low levels and can be corrected by supplements.
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