Vitamin B12 – Cobalamin

Vitamin B12, also known as cobalamin, is a water-soluble vitamin naturally found in animal products such as meats, fish, eggs, milk and milk products such as yoghurts and cheeses or found in fortified products such as vegan milk and yoghurts, some flours and breakfast cereals. This vitamin is known to play a part in controlling appetite and helps to release energy from foods, vital for a healthy nervous system as it is a key player in the function and development of brain and nerve cells and is needed during periods of rapid growth especially during the young age. Vitamin B12 is needed to form red blood cells and DNA; it is also involved in the use of folate (vitamin B9).

Vegans and vegetarians are likely to be deficient in vitamin B12 because it is not found in plant sources; Novel vegan food products are now fortified with vitamin B12 to support the body needs.

A water-soluble vitamin is a vitamin that can dissolve in water; this essentially means the vitamin can be easily transported around the body to be absorbed by tissues and organs. Other water-soluble vitamins are Vitamin C (ascorbic acid), Vitamin B1 (thiamine), Vitamin B2 (riboflavin), Vitamin B3 (niacin), Vitamin B5 (pantothenic acid), Vitamin B6 (pyridoxine), Vitamin B7 (biotin) and Vitamin B9 (folic acid or folate). Nutritional studies showed that a deficiency in any of these water-soluble vitamins will result in a clinical syndrome that may cause a severe morbidity or mortality. We aim to cover other vitamins in future articles.

Deficiency of vitamin B12

Symptoms of a deficiency in cobalamin include:


A degeneration of the spinal cord

Poor hair growth


Eczema or dermatitis

Sore muscles

Poor memory

In addition, some studies have found associations between vitamin B12 deficiency or low vitamin B12 intakes and depression. In pregnant and breastfeeding women, vitamin B12 deficiency might cause neural tube defects, developmental delays, failure to thrive, and anemia in offspring.


Fatigue– An inadequate intake of vitamin B12 causes anaemia, a condition in which a shortage of oxygen-carrying red blood cells results in excessive tiredness. Vitamin B12 supplements and injections are prescribed by doctors to treat many problems that affect energy levels.

Mood issues– vitamin B12 appears to be involved in the production of the brain’s feel-good chemicals serotonin and dopamine, which control mood and sleep patterns. An increased intake of vitamin B12 may alleviate depression and improve mood overall.

Pernicious anaemia-the form of anaemia that develops when there is a lack of vitamin B12 can be treated successfully with injections of vitamin B12.

Age-related macular degeneration (AMD)– Vitamin B12 has been associated with the development of age related macular degeneration (AMD) and risk of frailty, both leading causes of disability in the elderly. Research showed that patients at risk of vascular disease found a 34% reduction in the relative risk of AMD after supplementation with vitamins B12, B6 and folate respectively.

Groups at Risk of Vitamin B12 Inadequacy

The following groups are among those most likely to be vitamin B12 deficient. The groups include: older adults, individuals with pernicious anemia, individuals with gastrointestinal disorders or who have had a gastrointestinal surgery, infants of vegan women, vegetarians and vegans.


Unlike most water-soluble vitamins, some amount of B12 can be stored in the liver. In addition, multivitamin tablets usually contain 1 mcg of vitamin B12 which is sufficient for an average person to remain healthy and avoid deficiency. Strict vegetarians and vegans will need to take supplements or consume foods fortified with vitamin B12.

Cobalamin as a supplement.

Food sources of vitamin B12

As mentioned above, the food sources of vitamin B12 are principally of animal origin and include liver, beef, pork, salmon, white fish, eggs, milk, fortified breakfast cereals and some yeast extract.

There are no naturally occurring bioactive forms of vitamin B12 in plant sources. Some plant foods contain added vitamin B12 and others e.g. seaweed and mushrooms contain vitamin B12 analogues that are inactive in humans, although some studies suggest certain types of Japanese seaweed (nori) have prevented vitamin B12 deficiency in vegans.

Vitamin B12 binds to the protein in the foods we eat. In the stomach, hydrochloric acid and enzymes unbind vitamin B12 into its free form. From there, vitamin B12 combines with a protein called intrinsic factor so that it can be absorbed further down in the small intestine.

Drug-nutrient Interactions

Some medications are thought to interfere with the absorption or metabolism of vitamin B12. These include proton pump inhibitor (PPI) medications, metformin, nitrous oxide anaesthesia, some epileptic medications and colchicine.


Vitamin B12 is a water-soluble vitamin, so any unused amount will exit the body through the urine (although some excess will be stored by the liver). Generally, up to 1000 mcg a day of an oral tablet to treat a deficiency is considered safe. The Institute of Medicine states “no adverse effects have been associated with excess vitamin B12 intake from food and supplements in healthy individuals.” However, it is important not to start a high-dosage supplement of any kind without first checking with your doctor.


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