Vitamin B12 or cobalamin is one of the most important B vitamins that essentially required for the production and maturation of RBC, cellular metabolism, DNA synthesis, and nerve functions. Deficiency of Vitamin B12 is considered as the main cause of developing pernicious anaemia hence this vitamin is known as anti-pernicious anaemia vitamin. It is only found in animal source thus vegans are more prone to develop cobalamin deficiency.
Chemistry
- Vitamin B12 is an important water-soluble vitamin
- It has seen that among every vitamin, Vitamin B12 has very complex structure and it is composed of corrin ring with a cobalt atom at center. This corrin ring contains four pyrrole units among which two units are bound with each other directly and remaining two units are connected through methane bridge
- It has four vitamers (related chemical forms) that include cyanocobalamin, methylcobalamin, hydroxycobalamin and adenosylcobalamin
Interrelation of Vitamin B12 with folic acid
- Deficiency of Vitamin B12 or folic acid develop similar type of anaemia that indicates a probable biochemical relationship between them
- It has seen that the activity of the enzyme named homocysteine methyltransferase reduced in Vitamin B12 deficiency.
- This enzyme is responsible for converting N5-methyl THF to tetrahydrofolate (active form of folic acid). Deficiency of this enzyme is responsible for blocking the respective pathway and leads to the reduction of THF pool in body, as a result entire body folate get trapped as N5-methyl THF, this is termed as folate trap. This is how Vitamin B12 deficiency is related with the functional deficiency of folate and causes megaloblastic anaemia. Consumption of Vitamin B12 and folate combined diet is beneficial for preventing this type of anaemia
- It has also seen that both vitamins are functioning closely for improving iron utilization and RBC synthesis
Absorption, transport and storage of cobalamin
Vitamin B12 can only be able to perform its tasks if it is absorbed properly within blood and transported to every cells of the body. Below chart will show an overview of the absorption, transport and storage of Vitamin B12 -
Sources
Foods rich in Vitamin B12 are listed below –
- Meat like beef, ham, lamb and pork
- Animal liver
- Animal kidney
- Fish especially sardine, salmon, tuna
- Eggs
- Poultry like chicken, turkey
- Milk
- Curd
Health benefits
Role on RBC production
- It helps in the synthesis of RBC from bone marrow
- It also helps to mature RBC and maintains its small and round shape which makes RBC functionally active
- Deficiency of B12 is related with poor RBC production with abnormal shape (large and oval) that interferes with normal functioning of RBC and results in developing anaemia
Role on nervous system
- Myelin is an essential fat substance requires for the formation of myelin sheath which covers every neuron of central and peripheral nervous system and protects them from external injuries. Myelination of neuron is associated with effective and fast transmission of nerve impulse throughout the body
- Cobalamin helps to synthesize myelin and maintains the health and functionality of myelin sheath and hence prevents neurons from damages
Role on DNA synthesis
- It plays significant role in the synthesis of DNA as it helps to supply the methyl group essentially required for DNA synthesis
- It also helps in RNA and protein synthesis
- It has seen that Vitamin B12 and folic acid help in cell division
Role on bone health
- It has seen that Vitamin B12 helps in promoting the growth and development of bones
- It helps to enhance the bone mineral density and thus prevents the bone from becoming delicate and fragile
Role on preventing birth defects
- Vitamin B12 is one of the most important nutrients that required during pregnancy. It helps to support the growth of fetal nervous system and helps in synthesizing blood, DNA, RNA, proteins and new cells of fetus. Deficiency of maternal vitamin B12 contributes to still birth, preterm infants and increases the risk of miscarriages
- It has seen that women who have Vitamin B12 deficiency during their gestational period are more prone to give birth child with congenital anomalies (birth defects)
Role on vision
- Consumption of Vitamin B12 is beneficial for promoting vision as it helps to prevent the risk of developing macular degeneration (an eye disease that affects the vision)
- Elevated level of homocysteine is the main causative factor of macular degeneration and Vitamin B12 helps to reduce homocysteine concentration in blood and thus helps to improve the symptoms of the respective disease
Role on mental health
- Vitamin B12 helps in the synthesis and metabolism of serotonin, a biochemical substance of body responsible for regulating mood. It has seen that deficiency of Vitamin B12 is associated with developing a depressed mood as its deficiency causes a reduction in serotonin level
- It also helps to prevent depression and anxiety
Role on cardiac health
- Elevated level of homocysteine in blood is associated with increasing the risk of developing heart disease by facilitating clot formation within blood vessels
- Vitamin B12 helps to reduce homocysteine level in body and hence prevents the prevalence of cardiovascular diseases
Biochemical function of cobalamin
- Vitamin B12 in the form of methylcobalamin helps to synthesize methionine from homocysteine
- It has seen that degradation of certain amino acids or odd chain fatty acids or pyrimidines produce methylmalonyl-CoA, which is then converted into succinyl CoA (an important intermediate of TCA cycle) with the help of Vitamin B12 coenzyme
Recommended Dietary Allowance
- Adult males and females should consume 3µg of vitamin B12 daily for fulfilling its requirements
- Requirement of Vitamin B12 get increased during pregnancy and lactation and it is beneficial to consume 4µg of vitamin B12 per day for its increased requirement
- Children should consume 0.5 to 1.5 of Vitamin B12 daily
Disease states
It is better to consume cobalamin as per recommendation otherwise it may develop various health complications. Below table will show an overview of its deficiency and toxic symptoms -
| Deficiency disorders | Hyperactivity |
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Source:
Green, R., Allen, L.H., Bjørke-Monsen, A.L., Brito, A., Guéant, J.L., Miller, J.W., Molloy, A.M., Nexo, E., Stabler, S., Toh, B.H. and Ueland, P.M., 2017. Vitamin B 12 deficiency. Nature reviews Disease primers, 3(1), pp.1-20.
Langan, R.C. and Goodbred, A.J., 2017. Vitamin B12 deficiency: recognition and management. American family physician, 96(6), pp.384-389.
Moll, R. and Davis, B., 2017. Iron, vitamin B12 and folate. Medicine, 45(4), pp.198-203.
Obeid, R., Heil, S.G., Verhoeven, M., Van Den Heuvel, E.G., De Groot, L.C.P.G.M. and Eussen, S.J., 2019. Vitamin B12 intake from animal foods, biomarkers and health aspects. Frontiers in nutrition, 6, p.93.
Pannérec, A., Migliavacca, E., De Castro, A., Michaud, J., Karaz, S., Goulet, L., Rezzi, S., Ng, T.P., Bosco, N., Larbi, A. and Feige, J.N., 2018. Vitamin B12 deficiency and impaired expression of amnionless during aging. Journal of cachexia, sarcopenia and muscle, 9(1), pp.41-52.
Smith, A.D., Warren, M.J. and Refsum, H., 2018. Vitamin B12. In Advances in food and nutrition research (Vol. 83, pp. 215-279). Academic Press.
Watkins, D., Venditti, C.P. and Rosenblatt, D.S., 2020. Vitamins: cobalamin and folate. In Rosenberg's Molecular and Genetic Basis of Neurological and Psychiatric Disease (pp. 687-697). Academic Press.
Wong, C.W., 2017. Vitamin B12 Deficiency in the Elderly. In Nutrition and Functional Foods for Healthy Aging (pp. 159-166). Academic Press.
