Vitamin B12.
Vitamin B12 also called cobalamin, is a water-soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood. It is one of the eight B vitamins. It is not only involved in the metabolism of every cell of the human body, not only affecting the DNA synthesis and regulation, but also fatty acid synthesis and energy production. Vitamin B12 works together with folate in the synthesis of DNA and red blood cells. It also involves in the production of the myelin sheath around the nerves, and the conduction of nerve impulses. You can think of the brain and the nervous system as a big tangle of wires. Myelin is the insulation that protects those wires and helps them to conduct messages. Neither fungi, plants nor animals are capable of producing vitamin B12. Only bacteria have the enzymes required for its synthesis, although many foods are a natural source of B12 because of bacterial symbioses. The vitamin is the largest and most structurally complicated vitamin and can be produced industrially only through bacterial fermentation synthesis. Vitamin B12 was discovered from its relationship to the disease pernicious anaemia, which is an autoimmune disease in which parietal cells of the stomach which are responsible for secreting intrinsic factor are destroyed. Intrinsic factor is crucial for the normal absorption of B12, so a lack of intrinsic factor, as seen in pernicious anaemia, causes a vitamin B deficiency.
The function of Vitamin B12
Vitamin B12 has many important functions in the body.
• It works with Vitamin B (folate) to make our body’s genetic material.
• It helps to keep the levels of amino acid homocysteine in check, which may help decrease the risk of heart disease.
• It is essential for the production of red blood cells, which carry oxygen through the blood to the body’s tissues.
Sources
Vitamin B12 is synthesized by bacteria present in the intestine of every human being. Other than that this vitamin is also found in skimmed milk and vegetarian foods like fortified cereals and soya. A little amount of B12 is also present in vegetables. Fish and eggs have a good amount of Vitamin B12 but they are not to be consumed by the heart patients as they are having a very high content of Cholesterol.
Causes of Vitamin B12 Deficiency
Vitamin B12 deficiency is very rare as the body’s requirements are very low. Vitamin B12 deficiency can have a number of possible causes. Typically it occurs in people whose digestive systems do not adequately absorb the vitamin from the foods they eat.
This can be caused by:
• Pernicious anaemia, a condition in which there is a lack of a protein called intrinsic factor. The protein, which is made in the stomach, is necessary for vitamin B12 absorption.
• Atrophic gastritis, a thinning of the stomach lining that affects up to 30% of people aged 50 and above.
• Surgery in which part of the stomach and/or small intestine is removed.
• Conditions affecting the small intestine, such as Crohn's disease, celiac disease, bacterial growth, or a parasite.
• Excessive alcohol consumption.
• Autoimmune disorders, such as Graves’ disease or Systemic Lupus Erythematosus.
• Long term use of acid-reducing drugs.
Symptoms of Vitamin B12 Deficiency
• Weakness, tiredness or light-headedness
• Stomach upset and weight loss
• Rapid heartbeat and breathing
• Diarrhoea and constipation
• Pale skin
• Tingling and numbness in the toes
• Sore tongue
• Difficulty in walking
• Easy bruising or bleeding, including
• Memory loss, disorientation bleeding gums and dementia
Treatment for Vitamin B12 Deficiency
Vitamin B12 deficiency treatment depends on the cause of the deficiency. If pernicious anaemia or a problem with absorption is the cause, B12 replacement will be necessary. Most often this is given by injection; some people may be prescribed vitamin tablets.
For some people, B12 supplementation may be necessary for life. If a diet lacking in animal products is the cause, the doctor will recommend dietary changes along with supplementation of vitamin B12 by injection or tablet. For most people, treatment resolves the anaemia; however, any nerve damage that has occurred as a result of the deficiency could be permanent. A dose of 5-10 mg of folic acid daily is effective. Patients who have less than 5g/dl of haemoglobin need a blood transfusion. Iron and B12 are often required before a full haematological response can occur.
Dr atima Gupta
Consultant pathologist