Vitamin B12 has the largest and most complex chemical structure of all the vitamins and it contains cobalt ion. That is why it is called cobalamin.

Human body needs methyl cobalamin and 5-deoxyadenosyl cobalamin. Most of the supplements contain cyanocobalamin which is readily converted to methylcobalamin and 5-deoxyadenosyl cobalamin in the body.

The functions of vitamin B12 include:

• Needed for building proteins
• For the production of red blood cells
• Normal function of nervous system
• Important to our metabolism, e.g. DNA synthesis, regulation of fatty acid synthesis
• Important for the transfer of hydrogen atom between two adjacent atoms, transfer of methyl group between two molecules and removal of halogen atom from an organic molecules in the body

The deficiency symptoms include:

• Decreased red blood cell production leads to pernicious anaemia
• Affects the gastrointestinal tract resulting nausea, vomiting, bloating, gas, heartburn, diarrhoea or constipation, loss of appetite and weight loss
• Can damage the nervous system with all the negative symptoms like numbness and tingling in the hands and feet, unsteadiness, difficulty walking, confusion, depression, memory loss, and dementia
• Pale skin, cold hands and feet, weakness, sore mouth and tongue
• Confusion or dementia

The overdose side effects include:

• Can increase the danger of narrowing blood vessels in patients receiving coronary stents
• Skin problems
• Peripheral vascular thrombosis
• Can worsen liver diseases
• Can cause loss of fibres in optic nerve
• High numbers and abnormal red blood cells
• Allergy or sensitivity to cobalt or cobalamin

The recommended dietary allowance (RDA) for an adult is 2.4 microg per day. The RDA for pregnant women is 2.6 microg per day and lactating women is 2.8 microg per day. Excess vitamin B12 should not be taken during pregnancy and lactation.

Organ meat, milk and dairy products, egg, fish, clams and oysters are rich in vitamin B12.

Vegetarians can get vitamin B12 from Brewer’s yeast or nutritional yeast or from vitamin B12 fortified soy milk and cereals.

The vitamin B complex tablets have different amounts of vitamin B12. Consult your doctor always before you decide for a supplement.