Vitamin B12 or hydroxocobalamin is a water soluble vitamin. Actually, cobalamins include the whole group of compounds called B12. The group in the molecule connected with divalent cobalt gives the certain cobalamin its name. Cyanocobalamin is a term that is frequently used as an equivalent of vitamin B12. In vitamin preparations, hydroxocobalamin is generally used (it dominates in the blood serum) because it is preserved in the organism for a longer period of time than cyanocobalamin (mainly due to its longer half-life).
Which foods contain the vitamin?
- Black pudding
Food of animal origin is virtually the only important source of vitamin B12.
Biological functions of the vitamin
Realised in coenzyme forms. Human organism needs the coenzymes of hydroxocobalamin in two reactions. First, to methylate RNA and to reproduce methionine from homocystein and, second, to convert methylmalynol-CoA to succinyl-CoA in the catabolism of branched chain amino acids (threonine, isoleucine, valine).
Hydorxocobalamin is also needed in the metabolism of folic acid, synthesis of nucleic acids, functioninf of pantothenic acid and vitamin C and the development of erythocytes, synthesis of myelin and the normal development of skin.
Absorption, storage and excretion
Is absorbed in combination with intrinsic factor in ileum, mediated by receptors, whereas the process itself is saturated, which means that during each meal, 1–3 μg of vitamin B12 is absorbed and the synthesis of new intrinsic factors may take up to hours. Therefore, the additional administration of hydroxocobalamin does not have an effect, if there is sufficient amount of vitamin B12 in the organism. Absorption is inhibited by excessive alcohol, coffee, smoking, oral contraceptives, stomach hypoacidity, underproduction of intrinsic factors, calcium and iron deficiency in food and the use of laxatives.
The microflora of large intestine also synthesises small amounts of hydorxocobalamin.
The absorption of vitamin B12 decreases in old age.
This vitamin is mainly stored in liver but also in bone marrow, kidneys and pancreas. The supplies last for 1–3 years.
Problems resulting from deficiency
- Memory gaps
- Menstrual cycle disorders
- Unpleasant body smell
- Megaloblastic and pernicious anaemia
- Sore and cracked lips
- Dry tongue
- Schizoid symptoms (delusions)
- Progressive demyelinisation
Deficienciy is mainly the result of malabsorption, only very rarely due to the lack of vitamin in food.
Risk groups for developing the deficiency
- Patients with removed stomach or small intestine
- Persons with tapeworm
- Elderly people
- Pregnant and nursing women
- Long-term vegetarians
- Persons with stomach hypoacidity
- Patients who have the function disorders of the exocrine part of pancreas
Allergic reactions such as hives and skin eczema may occur.
Use of vitamin preparations
As an additional treatment component, vitamin B12 is used for treating alcoholism, peptic ulcer, gastritis, atherosclerosis, anaemia, osteoporosis and diabetes.
Figure 1. Vitamin B12: hydroxocobalamin
Vitamin B12 content in food
Quantities of food products which should be consumed daily to obtain the recommended daily amount of vitamin B12.
|Liver||5 g||10 g||14 g||14 g||14 g||18 g||18 g|
|Pork||187 g||373 g||522 g||522 g||522 g||672 g||672 g|
|Curd, 1%||179 g||357 g||500 g||500 g||500 g||643 g||643 g|
|Yoghurt, 2,5%||521 g||1042 g||1458 g||1458 g||1458 g||1875 g||1875 g|
|Cheese, 25%||78 g||156 g||219 g||219 g||219 g||281 g||281 g|
|Salmon||20 g||40 g||56 g||56 g||56 g||73 g||73 g|
|Egg||54 g||109 g||152 g||152 g||152 g||196 g||196 g|
|Black pudding||568 g||1136 g||1591 g||1591 g||1591 g||2045 g||2045 g|
|Liver||14 g||14 g||14 g|
|Pork||522 g||522 g||522 g|
|Curd, 1%||500 g||500 g||500 g|
|Yoghurt, 2,5%||1458 g||1458 g||1458 g|
|Cheese, 25%||219 g||219 g||219 g|
|Salmon||56 g||56 g||56 g|
|Egg||152 g||152 g||152 g|
|Black pudding||1591 g||1591 g||1591 g|